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
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!
Application:
Victor Reinz part numbers 4918(right bank) and 4923 (left bank) are available for GM 7.4L (454 CID)
engines.
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
mark iv blocks
mark v blocks
(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
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
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.
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
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
The rear of the block features new plug holes, similar to what GM did with the small-block casting.
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
GEN V and VI
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
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
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!
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!
Application:
Victor Reinz part numbers 4918(right bank) and 4923 (left bank) are available for GM 7.4L (454 CID)
engines.
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
mark iv blocks
mark v blocks
(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
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
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.
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
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
The rear of the block features new plug holes, similar to what GM did with the small-block casting.
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
GEN V and VI
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
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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