CHEVY BIG BLOCK VI

grumpyvette

Administrator
Staff member
Top 10 Reasons to Build Gen VI Big Blocks (NOTE NOT MARK V)
http://garage.grumpysperformance.com/index.php?threads/block-prep.125/


http://garage.grumpysperformance.com/index.php?threads/installing-splayed-caps.7267/#post-68837

http://garage.grumpysperformance.com/index.php?threads/427-tall-deck-bbc.14451/

http://hotrodenginetech.com/finding-vintage-big-blocks/

https://www.chevydiy.com/ultimate-guide-building-chevy-big-blocks-cylinder-blocks-instruction/

1. Standard production 4-bolt mains
2. Priority main oiling
3. One-piece rear main seal
4. Thicker deck surfaces
5. Thicker cylinder walls
6. Revised coolant passages
7. Accepts all Mark series cylinder heads
8. Machined fuel pump pad
9. Revised oiling to allow for bigger cam bearings/cam lift
10. Set up for roller cams or flat tappet cams

GEN VI blocks all have 4-bolt mains, priority main oiling and leak resistant 1-piece rear main seals. These cylinder cases have revised cylinders in either siamesed or open configuration and they provide thicker cylinder wall and deck surfaces for greater stability. They accept all common big block cylinder heads and they incorporate a fully machined fuel pump pad and provisions for either hydraulic or flat tappet lifters. Study the accompanying features to see how a GEN VI block can enhance your next big block build
Plus:

Bowtie Sportsman versions have splayed bolt main caps
Choice of siamesed or open cylinder bores
Can be drilled for use with 10-bolt front timing cover
Auxiliary oil pressure line added to front of block
Racing-style oil filter cast feature with added oil pressure port
Two bosses added for manual transmission clutch pivot (machined)
Additional material added around lifter bosses
Additional clearance added for roller timing chains

This is a cut and paste i stumbled on.
I know alot of people ask about this so I thought I would put it over here.
Big Block Chevrolet Gen V and Gen VI Oiling System
Solving the mystery of the Gen V and Gen VI Priority Main Oiling system

Priority Main Oiling System
The Generation V and VI big block Chevrolet blocks feature a priority main oiling system where the main oil supply passage is located adjacent to the camshaft tunnel. Drilled passages which intersect this large oil tunnel carry oil directly to the main bearings. If you are facing the front of the block with the engine in the upright position, this main oil supply tunnel is located in the 2 oÂ’clock position just below the right hand lifter oil supply line.
Oil Cooler Plumbing
Located along the oil pan rail just ahead of the oil filter pad are two drilled and tapped (3/8” NPT) oil passages for routing oil to an external oil cooler. The hole located closest to the oil filter pad (#2) is for the outgoing supply line to the oil cooler. The front passage (#1), which is farthest from the filter pad, is the return line from the oil cooler.
Careful examination reveals that these two passages intersect the same return line that feeds oil back to the main oil tunnel. This requires that a special fitting be used in the #2 supply line to prevent oil from short circuiting the oil cooler.
Part number SD1540 provides the necessary diverter basket to prevent the supply oil from entering the return line before going to the oil cooler. This fitting has a dash 10AN thread to allow the use of aftermarket components to plumb your external oil cooler. The front passage #1 will require a 3/8” NPT by dash 10AN adapter (#FCM2185), which is available from Scoggin-Dickey.
Understanding By-pass Valve Locations
Factory assembled 454, 502 engines and short blocks have two by-pass valves installed in the block. These factory installed by-pass valves (#25013759) will open at an 11 psi pressure differential. One by-pass valve is installed in the center hole on the oil filter pad (#4). This hole is the oil return passage from the oil filter. The second by-pass valve is installed in the adjacent hole (#3). The egg shaped hole (#5) is the high pressure oil supply passage from the oil pump.
For all racing application that will NOT use an oil cooler but will maintain the stock oil filter location, you must remove the center by-pass valve in location #4. Removing this valve eliminates three redundant right runs in the oil system. However, if you leave this by-pass in place the oil system will still function as it was intended, but a loss of oil pressure can result from the four right angle turns required for oil to return to the main oil tunnel.
If you intend to use a remote oil filter, a high pressure by-pass valve part number 25161284 must be installed in position #3. This valve will open at a 30 psi pressure differential. A plug will be installed in position #4 to prevent oil flow thru this passage. Oil should be returned to the block in the 3/8” hole located just able the oil filter pad. An oil filter block off plate kit (#SD3891) can be purchased from Scoggin-Dickey for Gen V and VI blocks to plumb your external oil filter.
If you intend to maintain the stock filter location and will use the factory provided oil cooler passages to install your oil cooler, then you must install two high pressure by-pass valves (#25161284). One will be installed in location #3 and the second in location #4.
Happy oiling
!
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There are gaskets made specifically for this swap. Use other gaskets at you're own risk- these are what you want (from a V/R press release, presumably prior to the Gen 6 engine release):

General Motors 7.4L Head Gasket
Issue:

General Motors (GM) 7.4L (454 CID) engines use two types of engine blocks: the Mark IV and Mark V. The Mark IV is found on 7.4L engines in model years from 1965 to 1990, and the Mark V is found on 7.4L engines in model years from 1991 and newer.

Often, installers will attempt to adapt a Mark IVcylinder head for a Mark V block. This conversion can be made if attention is paid to the coolant circulation. Mark IV and Mark V have different coolant flows and were originally designed for different head gaskets. If the conversion is not performed correctly, the engine will overheat, causing premature engine wear and damage.

Resolution:
Victor Reinz has designed two Nitroseal® head gaskets to specifically allow for this conversion. The installation requires Victor Reinz part number 4918 be installed on the right cylinder bank to maintain proper coolant circulation, and part number 4923 to be installed on the left cylinder bank for the correct coolant flow.
Chevy Performance BBC Bow Tie Race Engine Blocks | JEGS

Cast Iron Bow Tie Race Block Technical Notes
Precision CNC-machining means +/- 0.001'' tolerances
Standard deck (9.800'') or tall deck (10.200'')
4.240'' Finish Bore (4.600'' Maximum Bore, .250'' Minimum Wall Thickness)
A sonic bore check data sheet is provided with each block
Lifter bores are .300'' taller than standard blocks
Siamese cylinder bores
Improved cooling around number 1 cylinder
Accepts Mark IV or Gen V, Gen VI cylinder heads
Use Gen V head gaskets with Mark IV and Gen V cylinder heads
Use Gen VI head gaskets with Gen VI cylinder heads
Requires Mark IV design 2-piece rear main seal oil pans
Requires Mark IV design crankshafts
Can use Mark IV and Gen V, Gen VI camshafts, timing sets, lifters and timing cover
(aftermarket belt drive timing covers may require clearancing)
Blind-tapped head bolt holes; extra inner head bolt bosses provided
4-bolt SAE 8620 main caps splayed 16° on the three center mains
Priority main oiling wet sump system
Provisions for dry sump oil line provided
Honed camshaft and crankshaft bores
0.842'' lifter bores (maximum 1.06'') may be relocated
Distributor gear clearance at bottom of number 8 cylinder bore should be checked
Machined mechanical fuel pump pad
Tested to 1,200 horsepower!
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Application:
Victor Reinz part numbers 4918(right bank) and 4923 (left bank) are available for GM 7.4L (454 CID)
engines.
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BTW, , on BIG BLOCKS the oil pumps and oil filter adapters are different due to the block oil filter recess and rear seals being different
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mark iv blocks
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mark v blocks
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(keep in mind that ALL '91 and later Gen.V and Gen.VI big blocks come with 4-bolt main caps. The two-bolt big blocks are no longer in production
be aware that head bolts enter the block coolant passages,
so if you failed to dip the bolt threads in sealant when they were assembled,
through the heads coolant can seep up along the head bolts,
into the area under the valve cover
btw read this



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both of these work great at sealing head bolt threads,

MANY BUT NOT ALL aftermarket head designs have been modified to work on both the early MARK IV 1965-90 and later MARK V & VI blocks 1991-later.)

BTW, , on BIG BLOCKS the oil pumps and oil filter adapters are different due to the block oil filter recess and rear seals being different
GEN 4 or MARK IV
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IT helps to know exactly what year and casting number your engine block is as early production big block engines used a different rear cam bearing and cam, a potential rear cam bearing oil flow issue is found on the 1965- too a few very early 1967 engines ,if you install the older design BBC cam with a grooved rear main in EITHER config with EITHER rear bearing your covered, and since thats just not expensive and any decent machine shop can modify any cam like that cheaply is the smart route to take if your in doubt. obviously having the machine shop groove the rear cam journal under the cam bearing in the block like the later BBC engines would be ideal.

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1965396CamOilGroovea.jpg

http://garage.grumpysperformance.com/index.php?threads/cam-bearing-install-tools-install-info.1479/


http://garage.grumpysperformance.co...k-after-a-cam-lobe-rod-or-bearings-fail.2919/

http://garage.grumpysperformance.com/index.php?threads/cam-wear-articles-you-need-to-read.282/

GEN V and VI
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MARK VI BLOCK OIL CONNECTIONS

Big Block Chevrolet Gen V and Gen VI Oiling SystemSolving the mystery of the Gen V and Gen VI Priority Main Oiling system
Priority Main Oiling System
The Generation V and VI big block Chevrolet blocks feature a priority main oiling system where the main oil supply passage is located adjacent to the camshaft tunnel. Drilled passages which intersect this large oil tunnel carry oil directly to the main bearings. If you are facing the front of the block with the engine in the upright position, this main oil supply tunnel is located in the 2 o’clock position just below the right hand lifter oil supply line.

Oil Cooler Plumbing
Located along the oil pan rail just ahead of the oil filter pad are two drilled and tapped (3/8” NPT) oil passages for routing oil to an external oil cooler. The hole located closest to the oil filter pad (#2) is for the outgoing supply line to the oil cooler. The front passage (#1), which is farthest from the filter pad, is the return line from the oil cooler.

Careful examination reveals that these two passages intersect the same return line that feeds oil back to the main oil tunnel. This requires that a special fitting be used in the #2 supply line to prevent oil from short circuiting the oil cooler.

Part number SD1540 provides the necessary diverter basket to prevent the supply oil from entering the return line before going to the oil cooler. This fitting has a dash 10AN thread to allow the use of aftermarket components to plumb your external oil cooler. The front passage #1 will require a 3/8” NPT by dash 10AN adapter (#FCM2185), which is available from Scoggin-Dickey.

Understanding By-pass Valve Locations
Factory assembled 454, 502 engines and short blocks have two by-pass valves installed in the block. These factory installed by-pass valves (#25013759) will open at an 11 psi pressure differential. One by-pass valve is installed in the center hole on the oil filter pad (#4). This hole is the oil return passage from the oil filter. The second by-pass valve is installed in the adjacent hole (#3). The egg shaped hole (#5) is the high pressure oil supply passage from the oil pump.

For all racing application that will NOT use an oil cooler but will maintain the stock oil filter location, you must remove the center by-pass valve in location #4. Removing this valve eliminates three redundant right runs in the oil system. However, if you leave this by-pass in place the oil system will still function as it was intended, but a loss of oil pressure can result from the four right angle turns required for oil to return to the main oil tunnel.

If you intend to use a remote oil filter, a high pressure by-pass valve part number 25161284 must be installed in position #3. This valve will open at a 30 psi pressure differential. A plug will be installed in position #4 to prevent oil flow thru this passage. Oil should be returned to the block in the 3/8” hole located just able the oil filter pad. An oil filter block off plate kit (#SD3891) can be purchased from Scoggin-Dickey for Gen V and VI blocks to plumb your external oil filter.
http://www.superchevy.com/how-to/en...-big-block-casting-changes-through-the-years/
Here’s a Look at the Various Chevy Big-Block Casting Changes Through the Years
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With LS swaps all the rage these days, it’s easy to forget big-blocks are still alive and thriving. That’s because when it comes to making big power and even bigger torque, building it with a big-block is as easy as goading a smug Mustang driver into embarrassing himself at the stoplight.

Most enthusiasts know the basic big-block cylinder block casting was updated in the 1980s, but fewer know General Motors quietly updated the basic design of the block casting only a few short years ago to give it greater strength, greater performance capability, and make common much of the differences between the early, Mark IV blocks and later, 1980’s-type Gen V castings.

Big-block production engines were introduced, of course, in 1965 and remained in production with few changes for more than 20 years. Those are the Mark IV engines. In the late 1980s a new version arrived, designed primarily for marine and automotive fuel-injection applications. Those updated versions are referred to as the Gen V (and Gen VI) engines.

Distinguishing between Mark IV and Gen V blocks is easy: if it has a mechanical fuel pump mounting pad, it’s a Mark IV. If there’s no fuel pump pad, it’s a Gen V block. There are several other differences—particularly in the water jackets near the deck surfaces—that make some Mark IV and Gen V parts non-interchangeable, including crucial components such as cylinder head gaskets.

Within the last few years, General Motors revised the production-based big-block casting to accommodate features of the Mark IV and Gen V, enabling cylinder head and gasket interchangeability. It also features a mechanical fuel pump pad recast into the architecture. Other, less-visible changes to the basic casting include revised oiling to allow for larger camshaft bearings, thus higher camshaft lift. There has also been talk of creating extra clearance for roller timing chains, but as of our press deadline, that change hadn’t been implemented.

The latest block design is available from Chevrolet Performance (chevrolet.com/performance) under part numbers 19170538 and 19170540. The “0538” version comes with 4.250-inch finished bores to support 427- and 454-cubic-inch engines, while the “0540” block has larger-diameter 4.470 bores to build a 502-inch engine. Each can be overbored for a larger displacement, with the 0540 block supporting up to 4.500-inch bores. Notably, all of Chevrolet Performance’s crate engines use the revised casting design.

If you’re looking to build a mountain motor with an even larger bore, you’ll have to look at Chevrolet Performance’s Bowtie blocks, which support up to a 4.600-inch bore, or an aftermarket block.

For strength and parts interchangeability, the big-block castings’ specific changes and updates include a slightly beefier main web on the 0538 block, while both versions have revised water jackets near the deck surfaces, allowing Mark IV or Gen V head gaskets to be used interchangeably. The front bulkhead is revised, too. It is thicker and stronger, with marked provisions for a 10-bolt timing cover. Actually, the bulkhead is drilled and tapped for a conventional six-bolt cover, while the remaining holes must be finished by drilling out the prescribed positions. There is more material around the lifter bosses and a revised rear-of-block section allows for the machining of one- or two-piece main seals (similar to the Gen V design).

Oil pressure feed holes were added to the oil filter boss and front bulkhead to support oil feeds for superchargers, turbochargers, etc., while the oil hole next to the camshaft bore (at the front of the block) was repositioned to enable safe machining of the cam bore to accept a 50mm roller camshaft bearing. A new boss was added next to the distributor hole in the valley to support hardware for digital ignition equipment, and a front clutch boss has been added for older vehicle applications.

Also, a pair of new core plugs was added to the rear bulkhead. Chevrolet Performance says they enhanced the manufacturing process at the foundry and help improve overall quality. Also, a “Bowtie” emblem and other identifying marks were added to the Bowtie block, distinguishing it from previous castings.

In addition to the production-based “Mark”-type casting, Chevrolet Performance’s Bowtie block castings are designed for the highest-performance applications. They feature a few minor differences when compared with the Mark block, but include the common core’s updates for greater interchangeability. Most notably, the Bowtie blocks are machined for splayed main bearing cap bolts, whereas the “standard” versions feature production-style parallel main cap fasteners. The Bowtie blocks also have a distinctive water jacket design that allows the 4.600-inch bore capacity. There are seven part numbers offered for Bowtie blocks, some with the standard 9.800-inch deck height and one-piece rear main seal, and others with a tall, 10.200-inch deck height and two-piece rear main seal design.

There you have it: The big-block is renewed and improved after more than 50 years of stalwart performance. The updates will keep big-block engines viable for the foreseeable future and continue to prove the adage that there’s simply no replacement for displacement.
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The latest big-block casting has undergone significant updates to align the differences that distinguished earlier Mark IV and later Gen V blocks, while also strengthening the block and adding provisions that support greater performance.
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The most noticeable visual change to the latest design is the reintroduction of a mechanical fuel pump mounting pad machined into the passenger-side front corner of the block. Gen V blocks did not have this provision.
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The front of the block was revamped for greater parts interchangeability with the Mark IV and Gen V, including using 6-bolt or 10-bolt timing chain covers. (It comes with the 6-bolt cover holes machined, but is easily drilled and tapped for the 10-bolt cover.) Also, a Bowtie-style auxiliary pressurized oil line hole is machined near the bottom of the China wall.
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A revised oiling design (the oil hole next to the cam bore was repositioned) allows the camshaft bore to support the 50mm bearing of a roller-style, high-lift camshaft.

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The valley is mostly unchanged, but is machined for a roller-type valvetrain with more material cast around the lifter bosses. Also, a bolt boss is added next to the distributor boss to support digital ignition systems.
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Deck height specs remain unchanged at 9.800 inches for production-based blocks, but the water jackets beneath them are revised so that early Mark IV-type and later, Gen V-type head gaskets can be used interchangeably. Some versions of the Bowtie block are offered with a 10.200-inch deck height.
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The rear of the block casting is updated with a common core that enables the machining of one-piece or two-piece rear seals. This permits the engine to be fitted with and dressed like an early Mark IV engine, albeit with the modern block casting.

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There are subtle changes to the interior bulkheads that incorporate the Bowtie design into 8.2L Mark blocks; the smaller-displacement 7.4L Mark block is unchanged, due to knock sensor accommodations. There are subtle machining updates, too.


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All Mark-type blocks—such as the one seen here—are manufactured with production-style parallel four-bolt main caps. The race-oriented Bowtie casting features splayed mains.
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The rear of the block features new plug holes, similar to what GM did with the small-block casting.

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A new hole (shown at the very bottom of the photo) is added to the oil filter boss on the block to support a pressurized oil feed.
(keep in mind that ALL '91 and later Gen.V and Gen.VI big blocks come with 4-bolt main caps. The two-bolt big blocks are no longer in production
MANY BUT NOT ALL aftermarket head designs have been modified to work on both the early MARK IV 1965-90 and later MARK V & VI blocks 1991-later.)
BTW, , on BIG BLOCKS the oil pumps and oil filter adapters are different due to the block oil filter recess and rear seals being different
GEN 4 or MARK IV
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GEN V and VI
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Another major addition to the big-block casting is a clutch equalizer boss that makes the block a better fit for vintage muscle cars and their four-speed transmissions.
If you intend to maintain the stock filter location and will use the factory provided oil cooler passages to install your oil cooler, then you must install two high pressure by-pass valves (#25161284). One will be installed in location #3 and the second in location #4. Happy oiling!

SPRAYING ALL VALVE TRAIN COMPONENTS DURING ASSEMBLY WITH MOLY REDUCES FRICTION
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pre-spraying all bearing and valve train components with a moly based spray, helps embed micro moly lubricants in the metallic surface micro fissures , a good paste lube like cranes assembly lube over the spray surface helps insure a good lubricant surface coating, that is far stronger than just the ZINC and PHOSPHATES in oil
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Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
Coolant Routing Mk IV/Gen 5/Gen 6There are two different ways that coolant can be routed through the engine: series flow and parallel flow. Both ways work just fine. There may be a slight preference for parallel flow, but it is not a big deal. Series flow has the water exiting the water pump, flowing through the block to the rear, it then transfers through the head gasket and into the cylinder head through two large passages on each cylinder bank at the rear of the block. The coolant then travels from the rear of the head, forward to the front of the head, into the intake manifold water passage and out past the thermostat and thermostat housing. The water cools the block first, then it cools the head. The coldest water (coming out of the water pump) is directly below the hottest water (having already picked up the heat of the block and the head) as the hot water transfers into the intake manifold. By contrast, parallel flow has the water exiting from the water pump into the block, where a portion "geysers" up into the head between the first and second cylinder, another portion "geysers" up to the head between the second and third cylinders, another portion geysers up to the head between the third and fourth cylinder, and the remainder transfers to the head at the rear of the block. The coolant temperature inside the engine is more even that way. The differences in coolant routing is having (or not having) the three additional coolant transfer holes in each block deck, and three matching holes in the head gasket. The heads have passages for either system, and are not different based on coolant flow.

Be aware that gaskets that DO have the three extra holes between the cylinders often have restricted coolant flow at the rear--instead of having two large coolant transfer holes at the rear, there is only one, and it's the smaller of the two holes that remains. This is important because if you use a parallel flow head gasket on a series flow block, you can have massive overheating and there's NOTHING that will cure the problem except to replace the head gaskets with ones that don't restrict flow at the rear of the block, or to drill the block decks to allow the coolant to flow into the head between the cylinders. Here's why they can overheat: A series-flow block doesn't have the openings between the cylinders, no coolant can flow up to the head there. The gasket may only have the single, smaller opening at the rear, so the amount of water that gets through that opening is greatly reduced from what the block designers intended. The result is that the coolant flow through the engine is only a fraction of what is needed.

Most, but NOT all Mk IV engines are Series Flow. ALL Gen 5 and Gen 6 engines are Parallel Flow. A series flow block can be converted to parallel flow by drilling 3 holes in each deck surface, and then use parallel flow head gaskets. You can use the parallel flow gaskets as templates for locating the additional holes. It's really easy: Put the parallel flow gaskets on the block, mark the location and size of the three extra holes. Remove the gasket. Grab a 1/2" drill and a drill bit of the correct size, and pop the extra holes in the block. There is NO modification needed on the head castings. Some blocks have one of the holes already, but it needs to be ground oblong to properly match the gasket. Again, very easy with a hand held die grinder and rotary file.

I dug up some photos that may help. The holes in question are on the LOWER side of the deck surface, BETWEEN cylinders.

First: A Mark IV series-flow deck surface; painted white for visibility. There is only one coolant hole between cylinders; it's between #5 and #7. Note that hole's shape and position--Kinda "D" shaped with the flat side to the bottom; and very low on the deck surface.
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This image has been resized. Click this bar to view the full image.
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Quoted from and source
http://reviews.ebay.com/Big-Block-Ch...00000001563647
BlackoutSteve posted these pictures
What cylinder head?
With my 4.280" bore and AFR head, I am forced to use a 4.540" bore gasket because the chambers are wide and would otherwise allow the gasket to "hang" in the chamber.

For example..
428gaga.jpg

454gaga.jpg
This guide is intended to help you sort out the more major differences among Big Block Chevrolet engines produced since 1958. Chevrolet has designed and produced several different "big block" engine families. Within each family, there can be evolutionary changes, and special parts designed for competition use which may not be directly interchangeable with the regular production items. I don't intend to cover every possible variation. For practical purposes, all big block Chevrolet engines use a cylinder bore spacing of 4.84 inches although note the one exception below.

Early engines were designated as Mark I, (Mk I) Mk II, Mk III, and Mk IV. Later engines continued the numbering system as Generation 5 (Gen 5), Gen 6, Gen 7. There are some conflicting theories as to the reason for the change from "Mark" to "Generation". My first guess: "Gen 5" sounds much more modern, hi-tech, and trendy than "Mk V".

Mark I: The original "Big Block Chevy", also called the "W" engine perhaps because of the layout of the valves and therefore the shape of the valve covers--although another possibility is that GM chose the "W" prototype for production rather than the competing "X" or "Y" prototypes, and therefore it's a convenient coincidence that the valve layout is in the shape of a "W". It should be noted that this engine became "Mark I" only after the Mark II was being designed years after the "W" was introduced. Whatever the origin of the name, this engine family was installed in vehicles beginning in 1958, as a 348. In 1961, it went to 409 cubic inches, (as immortalized in the Beach Boys song "She's so fine, my 409") and for one year only (1963) a few well-connected racers could buy a car with a 427 cubic inch version called the Z-11. The 427 version was all about performance, and had special parts which were not directly interchangeable with the 348/409. While production of the 427 was severely limited, both the 348 and 409 were offered in passenger cars and light- and medium-duty trucks. The truck blocks were somewhat different from the passenger car blocks, having slightly different water jackets and of course, lower compression achieved by changes in the piston in addition to more machining of the top of the cylinder. A novel feature of this engine is that the top of the cylinders are not machined at a 90 degree angle to the bore centerline. The top of the cylinder block is machined at a 16 degree angle, and the cylinder head has almost no "combustion chamber" cast into it. The combustion chamber is the top wedge-shaped section of the cylinder. Ford also introduced an engine family like that in '58--the Mercury/Edsel/Lincoln "MEL" 383/410/430/462. The "W" engine ended it's automotive production life part way through the 1965 model year, when the 409 Mk I was superseded by the 396 Mk IV engine.

Mark II: This is more of a prototype than a production engine. It is the 1963-only "Mystery Engine" several of which ran the Daytona 500 race, and in fact won the 100-mile qualifier setting a new record. It is largely the result of engineering work by **** Keinath. Produced mainly as a 427 but with a few 396 and 409 cubic inch versions, all in VERY limited numbers. Even though it was intended as a NASCAR-capable engine, it had 2-bolt main caps. This engine was never installed in a production-line vehicle by GM, it only went to racers. And even though it was available in 1963, it has very little resemblance to the 427 Mark I "W" engine of the same year. The Mark II was a "breakthrough" design using intake and exhaust valves that are tilted in two planes--a canted-valve cylinder head, nicknamed the "Semi-Hemi" or "Porcupine" because it is "almost" a hemi head, and the valve stems stick out of the head casting at seemingly random angles. The engine was the subject of an extensive article in the May, 1963 Hot Rod Magazine. Because of NASCAR politics, Chevrolet was forced to sell two 427 Mark II engines to Ford after the '63 Daytona race, (to "prove" that it was a production engine, and therefore eligible to race in NASCAR events) and so this engine is not only the grandfather of the Mark IV and later big block Chevies, it's also the grandfather of the canted-valve Ford engines: Boss 302, 351 Cleveland and variants, and the 429/460 big block Ford. The bore and stroke of the 427 MK II is not the same as the 427 MK IV.

Mark III: Never released for production. This was rumored to be the result of GM/Chevrolet's proposed buyout of the tooling and rights to the Packard V-8 engine of the mid-to-late '50's. The Packard engine was truly huge, having 5" bore centers. The former president of Packard wound up at Ford after Packard folded, perhaps because of that, Ford was also interested in this engine. Ford wanted to make a V-12 variant from it just as Packard had once envisioned. One way or another, neither GM nor Ford actually went forward with the purchase.

Mark IV: The engine that most people think of as the "big block Chevy". Released partway into the 1965 model year as a 396, superseding the older 409. It is a development of the Mark II and using similar but not identical canted valve (semi-hemi/porcupine) cylinder heads. It was later expanded to 402 (often still labeled as a 396, or even a 400,) a 427, a 454, and a few "special" engines were produced in the late '60's for offshore boat racing as a 482. There was a 366 and a 427 version that each had a .400 taller deck height to accommodate .400 taller pistons using four rings instead of the more usual three rings. These tall-deck engines were used only in medium-duty trucks (NOT in pickup trucks--think in terms of big farm trucks, garbage trucks, dump trucks, school busses, etc.) The tall-deck blocks all had 4-bolt main caps, forged crankshafts, and the strongest of the 3/8 bolt connecting rods. All-out performance engines used 7/16 bolt connecting rods, along with other changes. This engine family was discontinued in 1990, with the Gen 5 appearing in 1991.

Gen 5: General Motors made substantial revisions to the Mark IV engine, and the result was christened "Gen 5" when it was released for the 1991 model year as a 454. There were 502 cu. in. versions, but never installed in a production vehicle, the 502s were over-the-parts-counter only. Changes to the Gen 5 as compared to the Mk IV included, but are not limited to: rear main seal (and therefore the crankshaft and block) were changed to accept a one-piece seal, oiling passages were moved, the mechanical fuel pump provisions were removed from the block casting, the machined boss for a clutch bracket was eliminated, the cylinder heads lost the ability to adjust the valve lash, and the coolant passages at the top of the cylinder block were revised. The changes to the coolant passage openings meant that installing Mk IV cylinder heads on a Gen 5 block could result in coolant seepage into the lifter valley. Frankly, the changes (except for the one-piece rear main seal) were all easily recognized as cost-cutting measures which also removed some quality and/or utility. All told, the Gen 5 engine was not well regarded by the Chevy enthusiasts because of the changes to the coolant passages and the lack of an adjustable valvetrain. As always, the aftermarket has provided reasonable fixes for the problems. The Gen 5 lasted only until 1995.

Gen 6: GM recognized that it did not make any friends when it designed the Gen 5, and so they chose to revise the coolant passages again when designing the Gen 6, allowing the older heads to be used without coolant seepage problems. The boss for the clutch bracket returned, but was generally not drilled and tapped. The non-adjustable valvetrain remained, as did the one-piece rear main seal. Some but not all Gen 6 454 (and not 502) blocks regained a mechanical fuel pump provision. Production engines installed in pickup trucks got a high-efficiency cylinder head, still canted-valve, but with a modern heart-shaped combustion chamber of about 100cc. The intake port has a "ski jump" cast into it to promote swirling of the intake air flow. All production vehicles with a Gen 6 used a 454 version, but over-the-counter 502s are available. The Gen 6 is sometimes referred to as the "Gen Fix" because it fixed a number of issues that disappointed enthusiasts when the Gen 5 was released. As an added bonus, most if not all Gen 6 engines use hydraulic roller lifters.

Gen 7: A very major revision of the previous engines resulted in the 8.1 liter/ 8100/ 496 cubic inch Gen 7 in 2001. The block gained .400 in deck height so it is the same height as the previous "Tall Deck" truck blocks, wider oil pan rails, and the cylinder heads have symmetrical port layouts instead of the previous 4 long/4 short port layout. Very little interchanges between the 8.1 liter engine and the previous Mark IV/Gen 5/Gen 6 engines. The head bolt pattern and even the firing order of the cylinders has been changed. There are some things that remained true to the previous Mk IV/Gen 5/Gen 6--the bellhousing bolt pattern, the side motor mount bolt pattern, the flywheel bolt pattern, and the exhaust manifold bolt pattern are the same. Note that the bolt holes are threaded for metric fasteners. The 8.1 is internally balanced, so you could install a flywheel/flexplate from a 396/427 Mk IV provided you use the correct bolts to suit the 8.1 crankshaft.

I have had a chance to compare Mark IV, Gen 5/6 and Gen 7 head gaskets. It seems to be possible--but very difficult--to install IV/5/6 heads on the Gen 7 block. GM did this on one show vehicle, it IS possible. You must move three head bolt holes in the block; and as the holes only move about 1/2 their diameter it would be difficult to plug the existing holes, re-drill the new holes, and still have enough strength in the deck surface. There are cooling system differences as well that must be addressed. I have NOT done this conversion; but I do have comparison photos of the head gaskets.
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There are gaskets made specifically for this swap. Use other gaskets at you're own risk- these are what you want (from a V/R press release, presumably prior to the Gen 6 engine release):

General Motors 7.4L Head Gasket
Issue:

General Motors (GM) 7.4L (454 CID) engines use two types of engine blocks: the Mark IV and Mark V. The Mark IV is found on 7.4L engines in model years from 1965 to 1990, and the Mark V is found on 7.4L engines in model years from 1991 and newer.

Often, installers will attempt to adapt a Mark IVcylinder head for a Mark V block. This conversion can be made if attention is paid to the coolant circulation. Mark IV and Mark V have different coolant flows and were originally designed for different head gaskets. If the conversion is not performed correctly, the engine will overheat, causing premature engine wear and damage.

Resolution:
Victor Reinz has designed two Nitroseal® head gaskets to specifically allow for this conversion. The installation requires Victor Reinz part number 4918 be installed on the right cylinder bank to maintain proper coolant circulation, and part number 4923 to be installed on the left cylinder bank for the correct coolant flow.
Application:
Victor Reinz part numbers 4918(right bank) and 4923 (left bank) are available for GM 7.4L (454 CID)
engines.

read the links
http://www.chevydiy.com/ultimate-guide-building-chevy-big-blocks-cylinder-blocks-instruction/

http://www.superchevy.com/how-to/4567-chevrolet-big-block-engine-generations/


http://www.chevydiy.com/gaskets-fasteners-guide-big-block-chevy-engines/


With a series-flow head gasket laid on top of the deck. Two coolant holes at the end of the deck on the right side are open. NO coolant holes between the cylinders are open (not even the existing one between 5 'n' 7); the gasket has no holes there for coolant to pass through.
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Lastly, that same series-flow deck with a parallel-flow gasket on top. Note that the gasket has the three coolant-flow holes between the cylinders; just below the head bolt holes. Two of those holes show a full "circle" of the white-painted deck surface; one of them is partially over the existing hole already in the deck so some white shows but is not a full "circle". You would DRILL the two holes the same size as the holes in the gasket; and OBLONG the existing hole to match the hole in the gasket. Three (not four) holes per deck are either added or modified to match the gasket.
My apologies for the photo being so dark where the rearmost coolant passages are in the deck and gasket; that gasket has ONLY the smaller hole at the rear and would cover (block) the larger opening. This is NOT a problem because you've added the additional area of the drilled/oblonged holes.
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ear.

12/13
All ’87-and-later Chevy blocks come with a one-piece rear-main seal. This requires the use of a late-model one-piece rear-main seal crank. Starting with the ’88s, most passenger-car engines converted to hydraulic roller cams that required a spider. This is a truck block where the spider mounting bosses are not drilled and tapped, because the truck engine used a flat-tappet cam. These can be easily drilled and tapped to mount the spider for a hydraulic roller cam.



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mark iv blocks
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mark v blocks
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(keep in mind that ALL '91 and later Gen.V and Gen.VI big blocks come with 4-bolt main caps. The two-bolt big blocks are no longer in production
MANY BUT NOT ALL aftermarket head designs have been modified to work on both the early MARK IV 1965-90 and later MARK V & VI blocks 1991-later.)

BTW, , on BIG BLOCKS the oil pumps and oil filter adapters are different due to the block oil filter recess and rear seals being different
GEN 4 or MARK IV
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GEN V and VI
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MARK VI BLOCK OIL CONNECTIONS
RELATED INFO
viewtopic.php?f=44&t=4543&p=12111&hilit=hemi#p12111
http://bangshift.com/general-news/ebay- ... never-run/

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0704ch_08_z+chevy_big_block+.jpg



most big block blocks will take a .060 over bore without issue some will take .100 but your almost sure to have very thin bore walls that won,t seal the rings well, and keep in mind many of those blocks have internal water passage rust issues after all many are 25-30 plus years old

bore x bore x stroke times 8 x .7854= displacement
example
a 4.310 " x 4.310" x 4.25" x 8 x .7854=496 cubic inches

read these links and sub links

viewtopic.php?f=69&t=1420

viewtopic.php?f=69&t=5123

viewtopic.php?f=69&t=6125

viewtopic.php?f=69&t=189

BUY A FEW REFERENCE BOOKS ITS MONEY VERY WELL SPENT

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several COMMONLY USED GEN IV BIG BLOCK HEAD GASKETS (PRE 1991 MUSCLE CARS)
Brand:Fel-Pro

Manufacturer's Part Number:1027

Part Type:Head Gaskets

Product Line:Fel-Pro Performance Head Gaskets

Summit Racing Part Number:FEL-1027

UPC:084113010279

Bore (in):4.370 in.

Bore (mm):110.998mm

Gasket Material:Steel core laminate

Compressed Thickness (in):0.039 in.

Compressed Volume (cc):9.700cc

Lock Wire:No

Quantity:Sold individually.

Notes:pre-flattened copper wire.
For Aluminum heads only.
Will not fit Gen V or GEN VI blocks.



Brand:Fel-Pro

Manufacturer's Part Number:10171

Part Type:Head Gaskets

Product Line:Fel-Pro Performance Head Gaskets

Summit Racing Part Number:FEL-10171

UPC:084113107351

Bore (in):4.540 in.

Bore (mm):115.316mm

Gasket Material:Steel core laminate

Compressed Thickness (in):0.039 in.

Compressed Volume (cc):10.346cc

Lock Wire:No

Quantity:Sold individually.

Notes:pre-flattened steel wire. Will not fit Gen V or GEN VI blocks.


http://www.summitracing.com/parts/cgt-c5816-027


http://www.summitracing.com/parts/cgt-c5816-030/applications/


http://www.summitracing.com/parts/fel-508sd/applications/

http://www.summitracing.com/parts/mrg-3150g/applications/

a couple known dependable engine builders
http://www.lewisracingengines.com/

http://www.straubtechnologies.com/

http://vortecpro454.com/
 
Last edited:

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
The 427ci Big-Block: Comparing L88, ZL1, ZZ427 Engines

http://garage.grumpysperformance.com/index.php?threads/block-prep.125/
http://www.felpro.com/technical/tecblogs/head-gasket-coolant-holes.html
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the upper closed chamber head is bath tube shaped to provide dual opposed quench areas that squish against the piston deck,
forcing the fuel air mix toward the central cylinder bore, the lower open chamber head combustion chamber was found to un-shroud the valves,\
thus increasing the cylinder fill efficiency especially at upper rpms.
the dome higher compression ratio pistons for both combustion chambers are similar in shape to the combustion chambers they are designed too be used with.
the closed chamber piston can be used with the larger open chamber combustion chamber , but its reduced volume results in less effective compression and the dome,
of the closed chamber dome is marginally restrictive to the flame front propagation.

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http://www.chevyhardcore.com/tech-stories/engine/the-427ci-big-block-comparing-l88-zl1-zz427-engines/



Since its inception, the 427 cubic-inch Chevrolet big-block has become a legend for engine enthusiasts around the world. Whether it’s a small-block stroker or big-block powerhouse, chills seem to find their way up the neck of those lucky enough to have one in their ride.

The first of a three-part installment will be dedicated to the series of 427 cubic-inch engines that were so popular in the late-60s musclecar era. Part one will take a look back at the early L88 and ZL1 engines and compare them to the modern day ZZ427. In the coming months, part two will show how to build a modern day ZL1 using the aluminum block still available from Chevrolet Performance and aftermarket parts. Finally, part three will cover what goes into building a modern day ZZ427 using parts from Chevrolet Performance.


The pre-production L88 big-block was introduced in 1967 and was first seen in passenger cars in 1969.

The Legendary L88

The L88 engine was introduced in 1967, and although it was only offered in production vehicles until 1969, its legacy has carried on for decades. Only the informed would have been impressed with a quick glance under the hood, however, each year brings about improvements, creating a legacy that has survived into modern times.


The L88 was produced from 1967 to 1969, and featured aluminum heads.

Although a forged-steel crankshaft with forged I-beam rods was used, the beam portion of the rod wasn’t quite up to the task of supporting nearly 500 horsepower for any length of time. A weak point was quickly identified, and it was cured the following year with a new, thicker connecting rod that included floating wrist pins and spiral-lock retainers. The 3/8-inch knurled shank rod bolts were also replaced with 7/16-inch smooth shanks.

The pistons were also forged. With the availability of high-octane leaded fuel, the compression ratio was higher than most street engines today. Static compression was calculated at 12.5:1 requiring at least a 103 octane fuel. The increased compression allowed the relatively short stroke of the 427ci engine to produce plenty of torque.

The L88 used the same solid lifter camshaft profile for all three years. Duration was advertised as 326 degrees on the intake, while the exhaust breathed a bit longer at 334 degrees. Lift at the valve was .540 and .560-inches for the intake and exhaust respectively. The aggressive cam profile also required a third inner damper spring to control the valves at speeds up to 7,000 rpm. Rocker arms were stamped steel and required a longer slot for the L88’s high lift. Pushrods were also a hefty 7/16-inch diameter.



L88 Aluminum cylinder heads.

Aluminum cylinder heads reduced the big-block’s overall weight by 70 pounds compared to the iron head versions. Closed combustion chambers were used with the first generation of L88 heads, and chamber size poured out at 106.8cc. Intake valves measured 2.19-inches and exhausts were 1.72-inches. Intake ports were a rectangular shape, and exhaust ports were squared-off to match up with the exhaust manifold.


Rectangular ports as used on the ZL1 and L88 heads are compared to oval ports used on trucks.

In 1969 significant improvements were made for the aluminum cylinder head. Intake ports were reshaped, and material around the spark plug was removed, allowing for 30 percent more airflow. The pop-up piston was also reshaped with airflow in mind. As a result of the 118cc open chamber and reduced piston volume, compression was lowered to 12.0:1. However, the improved design still resulted in more power. The exhaust ports were also rounded to match tube headers, further extending its power capabilities.

A dual-plane aluminum intake manifold was used, and the carburetor pad accepted a standard four-barrel Holley. The divided-plenum under the carburetor was milled down to create an open chamber on the high-rise intake. In 1969, the divider was trimmed down even further to accompany the better flowing cylinder heads.

Chrome valve covers and natural finish heads offered a more stylish look.

Only the intake manifold was left unpainted for the 1967 versions; the aluminum heads were covered in orange. Chrome valve covers were installed in 1968, and Chevy left the bare aluminum finish of the heads unpainted, making the engine a bit more aesthetically pleasing.

In order to compete in Production Class racing, the engine needed to be street legal from the factory. Although a PCV valve (Positive Crankshaft Ventilation) was widely used starting in 1963, the L88 utilized a road draft tube in 1967, which meant it could not be licensed in California. However, all vehicles, starting in 1968, were required to have a PCV system and a purified exhaust. As a result, even the high-performing L88s came with a belt-driven Air Injection Reaction (AIR) pump and PCV system. The government also mandated the installation of a heater and defroster on all street cars, requiring a heater hose connection on the intake manifold.

ASK LOTS TO QUESTIONS & SHOP CAREFULLY,
the better aftermarket aluminum blocks are both comparatively very expensive and noticeably lighter weight,
but do your research, as theres a big BIG difference in the structural rigidity, and strength, between the thicker aluminum blocks
designed for serious racing
and those designed mostly to reduce weight, and duplicate the original iron block dimension-ally

The Corvette was Chevrolet’s flagship performance car, and it was logical that the Bow Tie’s most powerful engine be featured in the Corvette. However, Zora Duntov previously argued that the early 348ci and 409ci engines would be detrimental to the car’s handling because of its weight. Nevertheless, big engines with big power dominated the 1960s, forcing the second generation of Corvette to be built with this in mind. The production of the aluminum head L88 in 1967 reduced the weight of the large displacement big-block to 610 pounds overall, but there were still pounds to shave.



Feeding The Animal


In 1967, the L88 engine was equipped with an 850 cfm vacuum-secondary Holley carburetor.

In 1969, Chevrolet switched to a mechanical-secondary carburetor.

The ZZ427 uses a 770 cfm vacuum-secondary carburetor from Holley, and the electric choke is fully functional.

Developing The Aluminum Block


While the heavy big-blocks were holding their own in the drag race scene and stock car racing, weight kept these powerhouses out of the Can-Am sports car series. For those guys, Chevrolet R&D had been supplying all aluminum 327ci small-block racing engines to Chaparral cars in Midland, Texas, since 1963. When rumor hit that Ford was releasing an all-aluminum 427ci for the 1968 season Vince Piggins and his product promotions group countered with an aluminum block 427ci Chevrolet to be offered to the Can-Am competitors.

Piggins was able to see beyond the Can-Am scene, and also lobbied to bring the aluminum block to production cars. Excited to trim some pounds off the L88 for the Corvette, Duntov supported the idea 100 percent. Fred Frincke, casting designer for the L88 aluminum head, was now on the production engineering team and designed the aluminum production block. In 1969, the ZL1 engine was born.

A Fledgling Legend: The ZL1

In addition to the second design L88 cylinder head, 1969 was a big year for the “Rat” engine, as Chevrolet offered its first all-aluminum big-block for production cars. The ZL1 was a Regular Production Option (RPO) for the Corvette, and a Central Office Production Order (COPO) for Carmaros that were strictly intended for racing.


The aluminum 1969 ZL1

The now-coveted block was made of 356-T6 aluminum and produced at the Tonawanda foundry in New York. A programmable five-axis, omni-mill, machining center, shaped the aluminum castings into the final state. Thicker decks, bulkheads, and cylinder walls were utilized with additional core supports, gussets, and reinforcement webs for strength. Cylinder liners were needed, and were made of cast iron. These liners were frozen and then placed inside of a heated block. When both returned to room temperature, they wer inseparable. All of the primary dimensions of the ZL1 block matched its iron sibling.

The aluminum block did feature a main oil galley that was moved next to the camshaft and offered a provision for an external dry-sump system. The use of additional head bolts also carried over from the competition blocks to production units. Two threaded tabs protruded into the lifter valley from of each deck to provide extra clamping force.



Other than the block and camshaft, the ZL1 was identical to the L88. Both used the second design cylinder head that flowed 30 percent better than the first. The ZL1 capitalized on the extra airflow by utilizing a more aggressive camshaft. Intake valve lift was increased .020 inches to .560 inches, while the exhaust reached .600 inches. Intake duration was reduced to 322 degrees advertised duration; the exhaust duration was unchanged from the L88 camshaft. An aluminum timing gear with nylon coated teeth was attached to the camshaft and driven by an inverted tooth chain.



Conservative power ratings for the ZL1 were averaged at 525 horsepower. Installing a set of tube headers helped the peak number grow closer to 600 horsepower, but all that power came with a hefty price tag attached and added $4,718.35 to the bill, doubling the price of a Corvette coupe. Sticker shock surely contributed to the rarity of this nostalgic masterpiece. Government regulations required lower-octane fuel and consequently lower compression ratios. Chevrolet added a longer stroke to make up for the lost power, and in 1970 the 454ci engine replaced the L88 and ZL1 engines. The only year it was offered in a production car was 1969.


The modern day ZZ427.

Everyone’s ZZ427

The L88 engine is one of the most popular big-block engines in Chevrolet’s history. While the aluminum-headed 427ci was only offered in production vehicles between 1967 and 1969, its demand carried on for decades. Chevrolet Performance resurrected the 427ci Rat from the grave, and packed in some modern goodies.

“The ZL1 and L88 were only produced for a couple of years and were designed to burn race fuel,” says Bill Martens, Chevrolet Performance special programs manager. “The modern-day ZZ427 has a pump-gas friendly 10.1:1 compression ratio, which makes this 427ci streetable.”



The bore and stroke dimensions have changed slightly. A 4.250-inch bore is just a tick smaller than the 60s version, while the stroke grew to 3.766 inches. Both the crankshaft and connecting rods are constructed of 4340 forged-steel, while the pistons are forged aluminum. The eight slugs have a smaller dome than the previous engines to reduce the compression ratio to 10.0:1, allowing the use of 92 octane pump gas. It still puts out a stout 480 horsepower.



The modern-day ZZ427 has a pump-gas friendly 10.1:1 compression, which makes this 427ci streetable. – Bill Martens, Chevrolet Performance
quote2.png


Camshaft designs have changed tremendously over the past 40 years, and the ZZ427 features the better performing, more reliable roller camshaft. The solid tappet lifters have been replaced with hydraulic rollers, eliminating lash adjustments for a maintenance free valvetrain. This allows for more power in lower RPM ranges, enhancing the drivability and power range for street applications. Duration is measured at .050-inch lift and comes out to 224 degrees for the intake and 234 degrees for the exhaust. Valve lift works out to .527 inches on the intake and .544 inches on the exhaust with the 1.7:1 aluminum roller rocker arms.


While the ZZ427 uses an iron block and aluminum heads like its L88 predecessor, the new versions are quite different than the old school production. Cylinder head intake ports are a true oval shape, and valve size stayed the same as the second generation old school heads. But, ovate wire beehive springs are used in place of the triple-spring setup, allowing for better valve control with less pressure, heat, and wear on the springs. Also, the combustion chambers have shrunk to 110cc.


Exhaust ports were rounded to match tubular headers for 1969.

The Gen VI iron block has the main oil gallery next to the camshaft, just like the ZL1, and all five main caps benefit from the extra clamping force of four bolts. A one-piece rear main oil seal replaced the two-piece design of the 60s, and the front timing cover is a six-bolt design with an integral timing pointer designed to house a high-strength, single row timing chain. The ZZ lifter bores are longer with a machined boss on the top edge that accepts roller lifters with dog-bone style retainers. Finally, the deck surface of the ZZ has a modified, teardrop-shape coolant passage, making any head gasket designed for the Mark IV big-block incompatible.

Whether it’s the popular aluminum-headed L88, an ultra-rare aluminum block ZL1, or a modern day ZZ427, it is certain that the 427ci has made an impression on the automotive enthusiast. Stay tuned for more as we cover what it takes to build one of these iconic big-blocks for yourself.

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the reduced diameter of beehive valve springs usually eliminates the rocker too retainer clearance issue

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Rear main seal leakage remains a problem on engines that still use 2-piece rear main seals. We all know the time honored method of offsetting the seal parting lines so they do not match the main cap to block interface. And many builders still incorporate a small bit of non-hardening sealer on the parting surfaces, but it is still a craps shoot even for experienced builders. For several years now a new type of rear seal has been making the rounds of racing engine builders with great success. This one piece seal from GST RACING SEALS TM is designed to be cut and twisted around the crankshaft for installation. While this seems extreme, it is in fact a brilliant solution.

The 1-pc seals are designated “F-Type” because they have built-in flexibility which enables the seals to be opened out around the crankshaft. Before assembly the seal is cut radially in one position using a very sharp blade. This enables the seal body to be opened & twisted around the crankshaft flange before the main bearing cap is installed. The seal has two lips. The flywheel side incorporates a bonded PTFE facing which holds crankcase vacuum without raising friction.

The oil control lip incorporates their highly efficient HD2 Bi-Directional Hydrodynamic helix feature which reduces seal drag & improves sealing reliability. Being bi-directional the seal can also be used in Marine engines with reverse rotation. A further advantage of the seal is that it only has one joint face which is installed towards the top of the engine for maximum effect. When installed the cut surfaces match perfectly and no sealant is required. The cut does not have to be made with any particular precision. It has been test with extreme angles and still works properly.

The seals have been in use for almost 4 race seasons without problems, and many users have advised that the seal solves all of the basic problems with the two piece seals i.e. oil leakage & poor vacuum handling. The BBC seals are being used in race engines at 25.0”Hg vacuum without problems & dyno tests have verified that the engine can produce both extra power & increased torque after fitting the F-Type Seal.

We installed the test seal in the accompanying photos on a 1000+ horsepower big block Chevy and found no leakage after 27 dyno pulls and a half a dozen passes on the car. The held 25" of vacuum consistently and performed flawlessly.

The F-Type seal program currently includes big and small block Chevys, Ford and Mopar seals, & they now offer the seals for Buick/Olds/Pontiac V8 for maximum coverages. GST Racing Seals are now being specified by major race teams, constructors, and engine builders in NASCAR, ARCA, NHRA Pro-Stock, BAJA Off-Road, and Australian Super V8.

Pricing is batch quantity-related but typically a larger Engine Builder may pay $35 – $45 each & a smaller purchaser perhaps $65 – $75 each.

Approved stocking U. S. Distributors include:

Fast Fish Auto Parts
Kannapolis, NC (Chrysler)
704-701-6658
http://www.fastfishautoparts.com

James Engineering (SBC and BBC)
2380 W Midway Blvd # 1
Broomfield, CO 80020
303-941-3970http://www.james-engineering.com

BOP Engineering (Jefferson, WI) (Buick/Olds/Pontiac
N3651 Schmidt Rd
Jefferson WI 53549-9768
Phone (920) 674-6058
http://www.bopengineering.com

Manufacturers Rep in Concord, NC
Randy Edwards
704-467-2698)

Manaufacturer
GST RACING SEALS TM
148 Earls Road
Southampton
SO14 6TL, U.K.
info@gstracing.co.uk
023 8022 4104

The General Motors Vortec 8100 V8 was introduced in 2001 fullsize Chevy and GMC pickup trucks, RVs, vans, and SUVs as an alternative to the then-new Duramax diesel for customers seeking maximum hauling capability without the sourcing hassles and cost of diesel fuel. Also popular in maritime applications, the nautical version marketed by Crusader was branded Captains Choice, a great name if ever there was one. Of concern to car crafters, the Vortec 8100 (also known by its RPO number L18, but we'll just call it the 8100 in this story) was never offered in Chevrolet passenger cars because its hefty cast-iron heads and block bring total engine weight to 761 pounds.

But there is still a strong following among light-truck and SUV enthusiasts, even though the 8100 has been out of production (for highway use) since 2010. And, yes, more than a few Camaros, Chevelles, Corvettes, and Novas have been treated to 8100 power at the hands of builders seeking something out of the ordinary. These guys inevitably turn to lightweight aluminum heads from the aftermarket to shed weight. The resulting 500-plus-incher may not rev to 7,000 rpm like an LS, but with another 150 lb-ft of torque off the line, who needs revs? Check around, 8100 swaps have become popular with a host of car builders looking for something different.






Back to the history lesson, the 8100 was part of a final wave of domestic, gas-burning truck engines that included the 1994 8.0L Dodge V10 and 1997 6.8L Ford V10. Volatile gasoline prices conspired with advances in diesel engine technology like direct injection and refined turbo systems to make these oil-burners more appealing than ever. This slashed demand for these comparatively thirsty gasoline powerplants, and only the Ford V10 remains in production today. Dodge pulled the V10's plug after 2003 (except for Vipers), while the last Vortec 8100 was assembled in December 2009.


The nautical version marketed by Crusader was branded Captains Choice, a great name if ever there was one.
While Dodge and Ford added cylinders to get the necessary displacement, for the Vortec 8100, GM simply took the venerable 454 big-block V8 crankcase and gave it a shot in the arm. Though not officially designated as such by the factory, enthusiasts refer to the 8100 as a Gen 7 big-block because it borrows from the Gen 6 454/502 heavily. Call it what you will, the 8100 was the result of GM bumping the Vortec 7400/454's 4.00-inch stroke to 4.37, thanks to longer connecting rods and a block with taller decks. Sharing the 454's 4.25-inch bore, a burly 496 ci resulted. Being a heavy-duty, truck-specific engine, four-bolt main bearing caps are used, but unlike traditional high-performance 396 through 502 blocks—where the end caps (numbers 1 and 5) got the usual two bolt caps—the 8100 takes it all the way with four-bolt caps at every location (like many diesels).

If all of this makes builders of traditional rat motors drool with visions of inexpensive 600-cube torque monsters based on recycled 8100 blocks, beware. Changes were made to the block's oil-pan rails, all fasteners are Metric, and the 18-point head-bolt pattern (two more than the 396–502) is radically different and doesn't begin to accept factory or aftermarket big-block heads. Thus, the 8100 block isn't of much use to traditional Chevy big-block builders, but as we'll see, all is not lost.

And about those heads; though an assembled 8100 may not look much different from the 454-based Vortec 7400 it replaced, the intake ports were radically reworked. Since its debut in 1965, the Chevy big-block's canted valves delivered excellent breathing characteristics, thanks to the moving valve head's trajectory away from the shroud-inducing cylinder wall. But due to the need to allow space for things like pushrods, water jackets, fastener bosses, and intake ports, non-symmetrical, siamesed intake ports resulted. In short, the engine inhales through two distinctly different-sized intake runners: two short and two long. The symmetrical exhaust ports are less compromised, but there was room for improvement in both areas.

gm-vortec-8100-v-8-engine.jpg
2/21
Improvement came from the LS1. One look at the tall, thin cathedral intake ports first used on the 1997 LS1 cylinder head will show that their designers were fixated on symmetry. By focusing on shaping the ports as close as possible to each other in terms of size, contour, volume, and flow capacity, the density and velocity of the intake charge entering each cylinder is closer to equal. The resulting cylinder pressure during combustion is then equalized—as are the spent gas-evacuation characteristics during the exhaust stroke—and a more efficient engine results. That the LS1 (and subsequent Gen III small-blocks) are potent is an understatement.

For the 8100, GM designers cast aside the big-block's traditional long-port, short-port intake design and applied the LS1's strategy of making each intake and exhaust port as close to the rest as possible. With the intake manifold removed, the 8100's evenly spaced intake-port openings are a foreign sight compared to the traditional siamesed ports of previous big-block heads. What worked on the LS1 also worked on the 8100, though as a truck-oriented workhorse, GM concentrated on low- and midrange torque production, so don't expect to see fist-sized orifices.

More than a few Camaros, Chevelles, Corvettes, and Novas have been treated to 8100 power at the hands of builders seeking something out of the ordinary.
The big-block's traditional canted valve layout was retained because it still works. So yanking an 8100 valve cover reveals the big-block's non-linear, "porcupine," valve-stem configuration and stud-mounted rocker arms. Overall, GM did a fine job of giving the "Rat" a new lease on life. But at 340 net horsepower in stock trim, there's plenty of unexplored potential on tap.

We recently got a call from Patrick Davis, owner of a 2006 Chevy Avalanche, who turned us on to the world of 8100 performance modifications, thanks to an engine rebuild performed by James Bostick and the guys at Bostick Racing Engines in El Cajon, California. It turns out there are lots of frustrated 8100 owners—on land and sea—who need more than 340 hp and 450 lb-ft of torque, but don't want to turn to diesels. They all go to Raylar Engineering for help. Raylar is the go-to shop with a full line of available rotating assemblies, camshafts, valvetrain and intake-manifold upgrades and even a line of Big Power aluminum cylinder heads. Raylar's website even shows how to swap an 8100 into a C3 Corvette! Let's dig in and see how Pat's Avalanche has improved.



gm-496ci-vortec-8100-v-8-engine.jpg
3/21
The 496ci Vortec 8100 appeared in 2001 as a replacement for the 454ci Vortec 7400. The 8100's 42 extra cubes, siamesed intake ports, and other improvements delivered 340 hp and 450 lb-ft of torque in stock trim. The outgoing 454 rated 290 hp and 410 lb-ft. This 2006 Chevy Avalanche's owner needed even more and put Bostick Racing Engines on the job.

gm-496ci-vortec-8100-v-8-engine-block-main-caps.jpg
4/21
The 8100 block bears external 8.1L markings for quick identification. With four-bolt main caps in all five positions, bottom-end strength is abundant and all-out builds can easily handle 7,000 rpm. Lacking a distributor-mounting hole, the factory crank trigger ignition is retained to fire the plugs. The 8100's main cap bolts torque to 110/100 lb-ft (inner/outer) at all locations. Believe it or not, the 8100 block is 20 pounds lighter than a 502 due to its thin wall casting.

raylar-engineering-stroker-kit.jpg
5/21
The dominant source for upgraded 8100 parts for land and sea use, Raylar Engineering offers everything needed to transform the 8100 into a stormer. The Raylar 4.75-inch stroker kit bumps displacement to 547 cubes using all forged rotating parts. Stock 8100 cranks and pistons are cast with powdered metal rods. Raylar's kit uses all forged parts and hard-anodized piston skirts with anti-friction coatings. The rotator can handle 800 hp and even turbocharging. Note the crank position tone ring at the tail of the crank (left).

gm-496ci-vortec-8100-v-8-engine-cylinder-barrels.jpg
6/21
The Avalanche block's seasoned bores are enlarged 0.030-inch to 4.280 to eliminate existing wear. The bottoms of the cylinder barrels require modest notching to clear increased swing arc of rods. Swapping 8100s into classic Chevys with manual transmissions requires a hydraulic clutch actuator. The 8100 block lacks the threaded receptacle for clutch pivot ball.

gm-496ci-vortec-8100-v-8-engine-with-raylar-540-stroker-assembly.jpg
7/21
The Raylar 540 stroker assembly grows to 547 with the 0.030-inch cylinder overbore. Swappers love the 8100 block for its combination of LS style and traditional motor-mount bosses. The dual circular holes tapped into the oil-pan rail ahead of the oil-filter pad connect to factory-stock external oil-cooler circuitry. The wider oil-pan rail doesn't accept non-8100 oil pans. Truck pans swapped into cars are aluminum and require modifications to fit.

raylar-big-power-cnc-aluminum-heads.jpg
8/21
Stock 8100 cast-iron heads weigh 78 pounds each and are not interchangeable due to a front-mounted coolant transfer tube. Raylar's Bigpower CNC aluminum heads weigh less than half that and interchange from side to side. Port flow at 0.300-inch lift is 240/176 cfm (I/E), 0.400 lift yields 295/201 cfm, 0.500 lift yields 330/229 cfm, and at 0.600 lift you'll see 341/252 cfm. More than 400-cfm flow numbers are possible with the CNC Extreme head option.

The resulting 500-plus-incher may not rev to 7,000 rpm like an LS, but with another 150 lb-ft of torque off the line, who needs revs?
raylar-intake-ports.jpg
9/21
At 315 cc, Raylar intake ports are significantly larger than stock 8100 heads (see sidebar). Raylar also embraced the LS-style, high-velocity, symmetrical intake-port configuration to feed its 2.19-diameter EV8 stainless intake valves. Manganese-silicon bronze valve guides and hardened steel valve seats are ready for anything from trailer hauling to turbocharged dragstrip duty.

raylar-exhaust-ports.jpg
10/21
Like the stock 8100, Raylar retains the good D-shaped exhaust port but with a larger 135cc volume. Exhaust valves measure 1.750-diameter and share necked 11/32 valve stems with intake side. Both seats feature a five-angle competition valve job. Optional CNC Extreme heads use 2.25/1.88 valves and extensive CNC porting to boost flow.

raylar-aluminum-heads-combustion-chambers.jpg
11/21
Like GM, Raylar's aluminum heads retain the benefit of the big-block's stock canted valve arrangement, as well as the stock guideplates and rocker studs. Fully CNC-machined 107cc combustion chambers bring compression ratio to 10:1 (9:1 is stock). Extra-thick 5/8-inch cylinder head decks ensure rigidity; the factory iron head decks are ½ inch.

raylar-aluminum-heads-with-double-valvesprings-and-chromoly-retainers.jpg
12/21
Up top, the Raylar Big Power castings come with double valvesprings and chromoly retainers providing 140 pounds on the seat at 1.900-inch installed height and 380 pounds at 0.600-inch lift. Stock 8100 valve covers must be used since the bolt pattern is different than traditional big-blocks—more on that in a moment. Beware, the stock 8100 is an all-Metric engine and its stock fasteners are all one-time-use, torque-to-yield items.

raylar-hydraulic-roller-cams.jpg
13/21
The 8100's LS-style port spacing and 1-8-7-2-6-5-4-3 firing order prevent the use of traditional big-block camshafts. Raylar honcho Larry Hofer says he's invested too much dyno time to give away the ideal cam specs. Thus, Raylar offers nine proprietary performance-proven hydraulic roller cams to suit applications from trailer towing to turbocharged drag racing. This trio depicts (left to right) the 203 (high-torque, stock-idle quality, emissions-compliant, safe with stock piston crowns), the 206 (for stock displacement or strokers with deep-relief pistons, choppy idle, 2,500-rpm stall recommended, improved midrange and top-end power), and the 213 (high lift, choppy idle, ideal for extra-displacement applications, requires Raylar deep-relief pistons). We pried, but all Hofer would say was that valve lift ranges between 0.500 and 0.660 lift. Call Raylar to make sure your pistons and cam are safely matched. Our 547 Avalanche runs the 206 cam. One benefit is the stock GM roller lifters can be reused if they're healthy.

gm-496ci-vortec-8100-v-8-engine-with-raylar-heads.jpg
14/21
Seasoned big-block builders will note the shortness of the Raylar chrome-moly rocker arm stud assemblies. The total installed height is low enough to fit beneath the stock 8100's pancake valve covers. The Raylar 1.7:1 cast stainless roller rockers gain 18 hp versus stock 8100 scrubber-type rockers. The top timing gear does double duty as cam position sensor trigger. Three gear and sensor assemblies were used (2001, 2002–2003, and 2004-up), so contact Raylar to ensure you've got the right parts. The head bolts torque to 55 lb-ft (long), 50 lb-ft (short), and with six fasteners clamping the gasket's fire ring around each bore, the 8100's gasket seal is unsurpassed in stock rat motor block history.

raylar-modified-manifold.jpg
15/21
The stock cast-aluminum 8100 intake manifold and 73mm throttle-body were meant for hauling and suppress airflow and power above 4,000 rpm. To complement our 547-cube long-block, Raylar offers this modified manifold with removed internal dividers, port matching, and a 90mm throttle-body for increased flow and power with the rpm ceiling climbing to 5,000. The stock 27-pound fuel injectors were at maximum duty cycle and gave way to Delco 42-pound squirters. All-out applications can make use of Raylar's fabricated aluminum Cool-Gap intake manifold or even a vertical eight-stack manifold with individual runners and ram tubes. When uncorked with these manifolds, crank speeds approaching 7,000 rpm are possible in all-out builds.

jba-headers.jpg
16/21
Perched on the engine stand, the completed 547-cube Vortec mill wears equal-length headers from JBA Headers. Designed for 2001–2006 8100-powered trucks, they're superior to stock manifolds and feature 2-inch primary tubes, 3-inch collectors, and are CARB approved. They cooperate with factory head pipes and catalytic converters for easy installation. Note the 8100's coil-near-plug ignition layout. The white ceramic spark-plug boots can withstand 2,000 degrees and are available from Raylar to prevent burned wires.

reprogrammed-ecu.jpg
17/21
Once installed in Davis' Avalanche, Bruce Tucker and the crew at JBA Speed Shop reprogrammed the ECU, then strapped the beast to their Mustang chassis dyno. If you're wondering how a 4x4 truck gets tested on a rear-wheel-only chassis dyno, thank the Avalanche's 4x4 on/off switch! The stock 8100 uses the same ECU as many LS engines (PN 12200411 and popularly referred to as the 0411), so reprogramming is no mystery. JBA updated the fuel trim, spark table, torque management, and the self-learning properties took it from there. Not used in Corvettes or Camaros, the truck-only, torque-management function retards timing to protect the transfer case against damage in extreme off-road situations. Passenger cars (fortunately) lack this detail.

dyno-results.jpg
18/21
The notoriously conservative Mustang chassis dyno delivered the news. Jumping off from the stock readings (220 hp at 3,940 rpm and 303 lb-ft at 3,400 rpm), the 51 extra cubes, free-breathing heads, greater cam timing, and hogged-out intake manifold brought 110 hp and 115 lb-ft to the party (330 hp at 4,600 rpm and 418 lb-ft at 4,000 rpm). Imagine this monster in a light Camaro or Nova!

Overall, GM did a fine job of giving the "Rat" a new lease on life. But at 340 net horsepower in stock trim, there's plenty of unexplored potential on tap.
Symmetrical Rat
A Look at the 8100 Cylinder Head

stock-combustion-chambers.jpg
19/21
The stock, 114cc, heart-shaped combustion chambers were designed for a 4.50-inch bore (the 8100 bore measures 4.25). The chambers overlap the 496's bores, which shrouds the stock 2.190/1.725-inch valves. Raylar's Big Power heads use smaller chambers to eliminate the shrouding problem. Raylar also added another quench area adjacent to the spark plug, which promotes faster combustion.

stock-intake-ports.jpg
20/21
Tall and skinny, the stock 8100 intake ports borrow from LS architecture and are virtually identical from cylinder to cylinder. The classic big-block's two short and two long intake-runner strategy was a compromise. Unfortunately, the 8100's extreme focus on thin wall casting for reduced weight prevents meaningful porting work, particularly at the short side radius, where help is most needed.

exhaust-ports.jpg
21/21
The 8100 head retains the D-shaped exhaust-port configuration first employed in 1979. Shown upside-down here, the concept is good, but the size is too small for high horsepower. Each cast-iron 8100 head weighs 78 pounds bare. Since the stock valvetrain is strictly non-adjustable, when swapping cams, be sure the stock base circle is retained to ensure proper lifter preload.

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Patriot Performance
Patriot Performance; 888/462-8276; Patriot-Performance.com

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937‐846‐1333
 
Last edited:

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member

The General Motors Vortec 8100 V8 was introduced in 2001 fullsize Chevy and GMC pickup trucks, RVs, vans, and SUVs as an alternative to the then-new Duramax diesel for customers seeking maximum hauling capability without the sourcing hassles and cost of diesel fuel. Also popular in maritime applications, the nautical version marketed by Crusader was branded Captains Choice, a great name if ever there was one. Of concern to car crafters, the Vortec 8100 (also known by its RPO number L18, but we'll just call it the 8100 in this story) was never offered in Chevrolet passenger cars because its hefty cast-iron heads and block bring total engine weight to 761 pounds.

But there is still a strong following among light-truck and SUV enthusiasts, even though the 8100 has been out of production (for highway use) since 2010. And, yes, more than a few Camaros, Chevelles, Corvettes, and Novas have been treated to 8100 power at the hands of builders seeking something out of the ordinary. These guys inevitably turn to lightweight aluminum heads from the aftermarket to shed weight. The resulting 500-plus-incher may not rev to 7,000 rpm like an LS, but with another 150 lb-ft of torque off the line, who needs revs? Check around, 8100 swaps have become popular with a host of car builders looking for something different.

Back to the history lesson, the 8100 was part of a final wave of domestic, gas-burning truck engines that included the 1994 8.0L Dodge V10 and 1997 6.8L Ford V10. Volatile gasoline prices conspired with advances in diesel engine technology like direct injection and refined turbo systems to make these oil-burners more appealing than ever. This slashed demand for these comparatively thirsty gasoline powerplants, and only the Ford V10 remains in production today. Dodge pulled the V10's plug after 2003 (except for Vipers), while the last Vortec 8100 was assembled in December 2009.

The nautical version marketed by Crusader was branded Captains Choice, a great name if ever there was one.
While Dodge and Ford added cylinders to get the necessary displacement, for the Vortec 8100, GM simply took the venerable 454 big-block V8 crankcase and gave it a shot in the arm. Though not officially designated as such by the factory, enthusiasts refer to the 8100 as a Gen 7 big-block because it borrows from the Gen 6 454/502 heavily. Call it what you will, the 8100 was the result of GM bumping the Vortec 7400/454's 4.00-inch stroke to 4.37, thanks to longer connecting rods and a block with taller decks. Sharing the 454's 4.25-inch bore, a burly 496 ci resulted. Being a heavy-duty, truck-specific engine, four-bolt main bearing caps are used, but unlike traditional high-performance 396 through 502 blocks—where the end caps (numbers 1 and 5) got the usual two bolt caps—the 8100 takes it all the way with four-bolt caps at every location (like many diesels).

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If all of this makes builders of traditional rat motors drool with visions of inexpensive 600-cube torque monsters based on recycled 8100 blocks, beware. Changes were made to the block's oil-pan rails, all fasteners are Metric, and the 18-point head-bolt pattern (two more than the 396502) is radically different and doesn't begin to accept factory or aftermarket big-block heads. Thus, the 8100 block isn't of much use to traditional Chevy big-block builders, but as we'll see, all is not lost.

And about those heads; though an assembled 8100 may not look much different from the 454-based Vortec 7400 it replaced, the intake ports were radically reworked. Since its debut in 1965, the Chevy big-block's canted valves delivered excellent breathing characteristics, thanks to the moving valve head's trajectory away from the shroud-inducing cylinder wall. But due to the need to allow space for things like pushrods, water jackets, fastener bosses, and intake ports, non-symmetrical, siamesed intake ports resulted. In short, the engine inhales through two distinctly different-sized intake runners: two short and two long. The symmetrical exhaust ports are less compromised, but there was room for improvement in both areas.
gm vortec 8100 v 8 engine
gm vortec 8100 v 8 engine

SEE ALL 21 PHOTOS
Improvement came from the LS1. One look at the tall, thin cathedral intake ports first used on the 1997 LS1 cylinder head will show that their designers were fixated on symmetry. By focusing on shaping the ports as close as possible to each other in terms of size, contour, volume, and flow capacity, the density and velocity of the intake charge entering each cylinder is closer to equal. The resulting cylinder pressure during combustion is then equalized—as are the spent gas-evacuation characteristics during the exhaust stroke—and a more efficient engine results. That the LS1 (and subsequent Gen III small-blocks) are potent is an understatement.

For the 8100, GM designers cast aside the big-block's traditional long-port, short-port intake design and applied the LS1's strategy of making each intake and exhaust port as close to the rest as possible. With the intake manifold removed, the 8100's evenly spaced intake-port openings are a foreign sight compared to the traditional siamesed ports of previous big-block heads. What worked on the LS1 also worked on the 8100, though as a truck-oriented workhorse, GM concentrated on low- and midrange torque production, so don't expect to see fist-sized orifices.
More than a few Camaros, Chevelles, Corvettes, and Novas have been treated to 8100 power at the hands of builders seeking something out of the ordinary.
The big-block's traditional canted valve layout was retained because it still works. So yanking an 8100 valve cover reveals the big-block's non-linear, "porcupine," valve-stem configuration and stud-mounted rocker arms. Overall, GM did a fine job of giving the "Rat" a new lease on life. But at 340 net horsepower in stock trim, there's plenty of unexplored potential on tap.
We recently got a call from Patrick Davis, owner of a 2006 Chevy Avalanche, who turned us on to the world of 8100 performance modifications, thanks to an engine rebuild performed by James Bostick and the guys at Bostick Racing Engines in El Cajon, California. It turns out there are lots of frustrated 8100 owners—on land and sea—who need more than 340 hp and 450 lb-ft of torque, but don't want to turn to diesels. They all go to Raylar Engineering for help. Raylar is the go-to shop with a full line of available rotating assemblies, camshafts, valvetrain and intake-manifold upgrades and even a line of Big Power aluminum cylinder heads. Raylar's website even shows how to swap an 8100 into a C3 Corvette! Let's dig in and see how Pat's Avalanche has improved.
gm 496ci vortec 8100 v 8 engine
gm 496ci vortec 8100 v 8 engine

SEE ALL 21 PHOTOS
The 496ci Vortec 8100 appeared in 2001 as a replacement for the 454ci Vortec 7400. The 8100's 42 extra cubes, siamesed intake ports, and other improvements delivered 340 hp and 450 lb-ft of torque in stock trim. The outgoing 454 rated 290 hp and 410 lb-ft. This 2006 Chevy Avalanche's owner needed even more and put Bostick Racing Engines on the job.
gm 496ci vortec 8100 v 8 engine block main caps
gm 496ci vortec 8100 v 8 engine block main caps

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The 8100 block bears external 8.1L markings for quick identification. With four-bolt main caps in all five positions, bottom-end strength is abundant and all-out builds can easily handle 7,000 rpm. Lacking a distributor-mounting hole, the factory crank trigger ignition is retained to fire the plugs. The 8100's main cap bolts torque to 110/100 lb-ft (inner/outer) at all locations. Believe it or not, the 8100 block is 20 pounds lighter than a 502 due to its thin wall casting.
raylar engineering stroker kit
raylar engineering stroker kit

SEE ALL 21 PHOTOS
The dominant source for upgraded 8100 parts for land and sea use, Raylar Engineering offers everything needed to transform the 8100 into a stormer. The Raylar 4.75-inch stroker kit bumps displacement to 547 cubes using all forged rotating parts. Stock 8100 cranks and pistons are cast with powdered metal rods. Raylar's kit uses all forged parts and hard-anodized piston skirts with anti-friction coatings. The rotator can handle 800 hp and even turbocharging. Note the crank position tone ring at the tail of the crank (left).
gm 496ci vortec 8100 v 8 engine cylinder barrels
gm 496ci vortec 8100 v 8 engine cylinder barrels

SEE ALL 21 PHOTOS

The Avalanche block's seasoned bores are enlarged 0.030-inch to 4.280 to eliminate existing wear. The bottoms of the cylinder barrels require modest notching to clear increased swing arc of rods. Swapping 8100s into classic Chevys with manual transmissions requires a hydraulic clutch actuator. The 8100 block lacks the threaded receptacle for clutch pivot ball.
gm 496ci vortec 8100 v 8 engine with raylar 540 stroker assembly
gm 496ci vortec 8100 v 8 engine with raylar 540 stroker assembly

SEE ALL 21 PHOTOS
The Raylar 540 stroker assembly grows to 547 with the 0.030-inch cylinder overbore. Swappers love the 8100 block for its combination of LS style and traditional motor-mount bosses. The dual circular holes tapped into the oil-pan rail ahead of the oil-filter pad connect to factory-stock external oil-cooler circuitry. The wider oil-pan rail doesn't accept non-8100 oil pans. Truck pans swapped into cars are aluminum and require modifications to fit.
raylar big power cnc aluminum heads
raylar big power cnc aluminum heads

SEE ALL 21 PHOTOS
Stock 8100 cast-iron heads weigh 78 pounds each and are not interchangeable due to a front-mounted coolant transfer tube. Raylar's Bigpower CNC aluminum heads weigh less than half that and interchange from side to side. Port flow at 0.300-inch lift is 240/176 cfm (I/E), 0.400 lift yields 295/201 cfm, 0.500 lift yields 330/229 cfm, and at 0.600 lift you'll see 341/252 cfm. More than 400-cfm flow numbers are possible with the CNC Extreme head option.
The resulting 500-plus-incher may not rev to 7,000 rpm like an LS, but with another 150 lb-ft of torque off the line, who needs revs?
raylar intake ports
raylar intake ports

SEE ALL 21 PHOTOS
At 315 cc, Raylar intake ports are significantly larger than stock 8100 heads (see sidebar). Raylar also embraced the LS-style, high-velocity, symmetrical intake-port configuration to feed its 2.19-diameter EV8 stainless intake valves. Manganese-silicon bronze valve guides and hardened steel valve seats are ready for anything from trailer hauling to turbocharged dragstrip duty.
raylar exhaust ports
raylar exhaust ports

SEE ALL 21 PHOTOS
Like the stock 8100, Raylar retains the good D-shaped exhaust port but with a larger 135cc volume. Exhaust valves measure 1.750-diameter and share necked 11/32 valve stems with intake side. Both seats feature a five-angle competition valve job. Optional CNC Extreme heads use 2.25/1.88 valves and extensive CNC porting to boost flow.
raylar aluminum heads combustion chambers
raylar aluminum heads combustion chambers

SEE ALL 21 PHOTOS

Like GM, Raylar's aluminum heads retain the benefit of the big-block's stock canted valve arrangement, as well as the stock guideplates and rocker studs. Fully CNC-machined 107cc combustion chambers bring compression ratio to 10:1 (9:1 is stock). Extra-thick 5/8-inch cylinder head decks ensure rigidity; the factory iron head decks are inch.
raylar aluminum heads with double valvesprings and chromoly retainers
raylar aluminum heads with double valvesprings and chromoly retainers

SEE ALL 21 PHOTOS
Up top, the Raylar Big Power castings come with double valvesprings and chromoly retainers providing 140 pounds on the seat at 1.900-inch installed height and 380 pounds at 0.600-inch lift. Stock 8100 valve covers must be used since the bolt pattern is different than traditional big-blocks—more on that in a moment. Beware, the stock 8100 is an all-Metric engine and its stock fasteners are all one-time-use, torque-to-yield items.
raylar hydraulic roller cams
raylar hydraulic roller cams

SEE ALL 21 PHOTOS
The 8100's LS-style port spacing and 1-8-7-2-6-5-4-3 firing order prevent the use of traditional big-block camshafts. Raylar honcho Larry Hofer says he's invested too much dyno time to give away the ideal cam specs. Thus, Raylar offers nine proprietary performance-proven hydraulic roller cams to suit applications from trailer towing to turbocharged drag racing. This trio depicts (left to right) the 203 (high-torque, stock-idle quality, emissions-compliant, safe with stock piston crowns), the 206 (for stock displacement or strokers with deep-relief pistons, choppy idle, 2,500-rpm stall recommended, improved midrange and top-end power), and the 213 (high lift, choppy idle, ideal for extra-displacement applications, requires Raylar deep-relief pistons). We pried, but all Hofer would say was that valve lift ranges between 0.500 and 0.660 lift. Call Raylar to make sure your pistons and cam are safely matched. Our 547 Avalanche runs the 206 cam. One benefit is the stock GM roller lifters can be reused if they're healthy.
gm 496ci vortec 8100 v 8 engine with raylar heads
gm 496ci vortec 8100 v 8 engine with raylar heads

SEE ALL 21 PHOTOS
Seasoned big-block builders will note the shortness of the Raylar chrome-moly rocker arm stud assemblies. The total installed height is low enough to fit beneath the stock 8100's pancake valve covers. The Raylar 1.7:1 cast stainless roller rockers gain 18 hp versus stock 8100 scrubber-type rockers. The top timing gear does double duty as cam position sensor trigger. Three gear and sensor assemblies were used (2001, 20022003, and 2004-up), so contact Raylar to ensure you've got the right parts. The head bolts torque to 55 lb-ft (long), 50 lb-ft (short), and with six fasteners clamping the gasket's fire ring around each bore, the 8100's gasket seal is unsurpassed in stock rat motor block history.
raylar modified manifold
raylar modified manifold

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The stock cast-aluminum 8100 intake manifold and 73mm throttle-body were meant for hauling and suppress airflow and power above 4,000 rpm. To complement our 547-cube long-block, Raylar offers this modified manifold with removed internal dividers, port matching, and a 90mm throttle-body for increased flow and power with the rpm ceiling climbing to 5,000. The stock 27-pound fuel injectors were at maximum duty cycle and gave way to Delco 42-pound squirters. All-out applications can make use of Raylar's fabricated aluminum Cool-Gap intake manifold or even a vertical eight-stack manifold with individual runners and ram tubes. When uncorked with these manifolds, crank speeds approaching 7,000 rpm are possible in all-out builds.
jba headers
jba headers

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Perched on the engine stand, the completed 547-cube Vortec mill wears equal-length headers from JBA Headers. Designed for 20012006 8100-powered trucks, they're superior to stock manifolds and feature 2-inch primary tubes, 3-inch collectors, and are CARB approved. They cooperate with factory head pipes and catalytic converters for easy installation. Note the 8100's coil-near-plug ignition layout. The white ceramic spark-plug boots can withstand 2,000 degrees and are available from Raylar to prevent burned wires.
reprogrammed ecu
reprogrammed ecu

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Once installed in Davis' Avalanche, Bruce Tucker and the crew at JBA Speed Shop reprogrammed the ECU, then strapped the beast to their Mustang chassis dyno. If you're wondering how a 4x4 truck gets tested on a rear-wheel-only chassis dyno, thank the Avalanche's 4x4 on/off switch! The stock 8100 uses the same ECU as many LS engines (PN 12200411 and popularly referred to as the 0411), so reprogramming is no mystery. JBA updated the fuel trim, spark table, torque management, and the self-learning properties took it from there. Not used in Corvettes or Camaros, the truck-only, torque-management function retards timing to protect the transfer case against damage in extreme off-road situations. Passenger cars (fortunately) lack this detail.
dyno results
dyno results

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The notoriously conservative Mustang chassis dyno delivered the news. Jumping off from the stock readings (220 hp at 3,940 rpm and 303 lb-ft at 3,400 rpm), the 51 extra cubes, free-breathing heads, greater cam timing, and hogged-out intake manifold brought 110 hp and 115 lb-ft to the party (330 hp at 4,600 rpm and 418 lb-ft at 4,000 rpm). Imagine this monster in a light Camaro or Nova!
Overall, GM did a fine job of giving the "Rat" a new lease on life. But at 340 net horsepower in stock trim, there's plenty of unexplored potential on tap.
Symmetrical Rat
A Look at the 8100 Cylinder Head
stock combustion chambers
stock combustion chambers

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The stock, 114cc, heart-shaped combustion chambers were designed for a 4.50-inch bore (the 8100 bore measures 4.25). The chambers overlap the 496's bores, which shrouds the stock 2.190/1.725-inch valves. Raylar's Big Power heads use smaller chambers to eliminate the shrouding problem. Raylar also added another quench area adjacent to the spark plug, which promotes faster combustion.
stock intake ports
stock intake ports

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Tall and skinny, the stock 8100 intake ports borrow from LS architecture and are virtually identical from cylinder to cylinder. The classic big-block's two short and two long intake-runner strategy was a compromise. Unfortunately, the 8100's extreme focus on thin wall casting for reduced weight prevents meaningful porting work, particularly at the short side radius, where help is most needed.

exhaust ports
exhaust ports

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The 8100 head retains the D-shaped exhaust-port configuration first employed in 1979. Shown upside-down here, the concept is good, but the size is too small for high horsepower. Each cast-iron 8100 head weighs 78 pounds bare. Since the stock valvetrain is strictly non-adjustable, when swapping cams, be sure the stock base circle is retained to ensure proper lifter preload.
Bostick Racing Engines: 619-792-3885

trust me my personal goal has been for several years,
to collect the parts required and knowledge to produce and install a larger displacement, EFI BBC engine,
connected to a 4l80E transmission i a personally owned c4 corvette,
modified with full manual control 4l80e trans in a C4 corvette with a dana 60 rear differential, I personally own,
I've helped 8 other people do similar engine swaps over the last 21 years, installing, chevy big block engines in their personal C4 corvettes ,
so I know what's involved, but I personally just never yet, have had the spare cash, to build my corvette the way I want to build it,
and since I refuse to compromise and slap something inferior, or sub-standard together,
its still a project I'm working on completing.
with the rapidly approaching future move its once more being delayed
if your going to do something I've learned you either do it correctly or wait until you can do so, or you'll always regret the results

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