BBC, larger, rectangle port intake on oval port heads?


The Grumpy Grease Monkey mechanical engineer.
Staff member
grumpy? I bought a really nice rectangle port intake at a local swap meet, for a damn good price, but my 454 has the crappy peanut port heads.... I have heard it will work if I use the rectangle port gaskets but I'm wondering if I will have other issues
A couple days of
reading the linked and sub-linked info
could save you a great deal of wasted time and money
and money spent on wrong or un-necessary parts
read the links and sub links below
a day or so spent doing reading and research,
(reading links and threads)
will frequently save you thousands of dollars and weeks of wasted work.
if you want a fast dependable car you will need to either do the research required to know exactly how and why things should work, or pay someone else to do the work that has taken that time and effort.
the most common mistake made by many people is that they fail to look at an engine as an interconnected group of component sub systems and they don,t realize that changes to a single component, no mater how much potential that component has is not going to allow that component or change in the potential to be realized until all the matched and supporting systems have similar potential.
the heads may be capable of flowing (x) on a stock engine but with careful selection of a cam with the correct duration and lift, and with a tuned header, and matching valve train mods along with some port and bowl clean-up the resulting improvements can be significantly more impressive.
larger intake manifold plenum volume TENDS to allow higher rpms
throttle body efi acts like a carb, as the injectors dump fuel/air in the plenum







direct port fuel injection has a separate, individual fuel injector feeding each cylinder, the plenum essentially runs mostly dry air free of fuel


worth watching, just for the tips on new head inspection
14092360...86-90...oval...OPEN...454 Truck, "peanut" round ports

Peanut port BBC cylinder heads may not be ideal for peak performance engine builds,, but they are far from useless, if your willing to do minor port and bowl clean-up and correctly match components, to maximize potential.
yes you could be ahead with decent aftermarket heads , but most of us don,t have the deep pockets to buy everything we would like too.

I would suggest you try it out, I've seen that combo work reasonably well in the past, it will seal and work on a functional basis, with the larger rectangle port gaskets that match the larger port size, but the sudden change in the port cross sectional area tends to reduce performance slightly,and can at lower rpms cause inconsistent fuel/air mixtures as the lip causes fuel to drop out of suspension, compared to a well matched intake design with runners similar in port cross sectional area.
but in a few cases the combo of overly large runners and plenum feeding the smaller ports, produces better results than the original intake if that intake was overly restrictive.
I at one time helped tune a guys car with peanut port heads, headers and adjustable valve train with new valve springs and a mild hydraulic, performance cam, similar to a crane, 103072 that he had installed, along with a rectangle port tunnel ram intake on that car.
I had my serious reservations at the time that it would work, but surprisingly, the tunnel ran with two 450 Holley carbs, once correctly set up and tuned,the combo provided a very noticeable boost in performance over the previous stock cast iron 4 barrel intake.
keep in mind the peanut port heads generally have a NON-ADJUSTABLE valve train and valve springs that will need to be upgraded to use any decent performance cam, and peanut port head benefit from port and bowl clean-up and a multi angle valve seat upgrade and better valve springs with adjustable rockers



carefully done, port work on the intake runners and plenum can produce significant flow rate improvements



rectangle port heads generally work best on 500 or larger displacement engines
with at least 10:1 compression and cams with at least 245 duration at .050 lift and valve lifts over .600 to take advantage of the potential port flow rates







Overheating – it’s a major concern for many after rebuilding or repairing an engine, especially if an overheat was the reason it had to be repaired in the first place. A recent trending topic on the Fel-Pro® Forum and social media pages is the relationship between overheating and the size and/or position of coolant holes in our head gaskets:

“I’m concerned that the coolant holes in the gasket are way smaller and not the right shape compared to the block.”

“…I noticed that the water jacket holes in the head gasket did not match those in the block and head.”

“Why are the water jackets restricted on the gaskets & can they be drilled out?”

“…the holes seem pretty small in the gaskets and some holes in the gasket are only half open on the head side. Should I open up the gasket holes to max the flow or are they this small for a reason?”

Controlling the temperature of an engine is critical for longevity and drivability. Overheating can lead to gasket failure, casting warpage and severe engine damage. At the same time, an engine that runs too cool will experience lower fuel economy, increased emissions and wear more quickly. The temperature an engine runs at needs to be properly regulated. The thermostat, radiator, and coolant play a big role in this – but they aren’t alone! Head gaskets are engineered with precisely shaped and sized holes to meter the flow of coolant through the engine.

Let’s take a look at a Big Block Chevy as an example – on the left we have a bare casting, on the right, a Fel-Pro head gasket is installed:


The coolant holes in the block casting are much larger than those in the Fel-Pro head gasket – this is by design!

To better visualize how much the coolant holes really control the flow of coolant, we’ve superimposed the gasket on the block:


Aside from the reduction in size of the top coolant holes, the large coolant hole on the bottom right is partially blocked off. There are also holes in the gasket which are not open in the block. Some Big Block Chevy engines have these holes while others do not. This will depend on the generation, application and the intended use of the block. These are not design flaws or oversights – the size and placement of every hole in the gasket is intentional, and this is true for every gasket we manufacture.

What is the purpose of using smaller holes in the head gasket or blocking off holes in the block?

The holes in the head gaskets are there to meter the flow of coolant properly through the heads. In most engines, coolant flows from the water pump at the front of the engine block toward the rear, goes up into the head(s), to the thermostat and finally to the radiator once the thermostat opens before returning back to the water pump.

An improperly sized or placed hole can create a “shortcut” which prevents coolant from following the correct “path” through the engine. If the coolant takes a “short-cut” because a coolant hole is too large at the front of the engine, the rear cylinders can overheat. If the holes are properly placed, but too large, the coolant can pass through the engine too quickly and fail to absorb enough heat, also resulting in overheating.

So why are the castings made with holes that are larger than they should be or unneeded for proper coolant flow? Engine blocks and heads are sand-cast, meaning sand forms the mold for the casting. The holes must be large enough, and sometimes extra holes must be added, to allow the sand to be completely cleaned from the casting once it has solidified. Also on older engines the holes may not always line up due to “core shift” – that is, the blocks are not always perfectly cast, so the gasket needs to accommodate the fact that different castings may have slightly different hole positioning.

Fel-Pro® Gaskets Design Philosophy

During the Fel-Pro head gasket validation process, we sometimes find that holes should be added, deleted, changed in size or moved to better control the flow of coolant through the engine. On certain applications, holes in the head or block will be fully or partially sealed off with the head gasket. While the visual differences may seem extreme, you can install Fel-Pro gaskets with confidence because every hole is precisely placed and sized to ensure that coolant flow is properly controlled by the head gasket.

With this in mind, a Fel-Pro head gasket should never be modified in any way – doing so not only prevents proper coolant flow, but also can affect the gaskets ability to seal, as the specialized coatings can be damaged.

Last edited:


"One test is worth a thousand expert opinions."
What years did they use those peanut ports? I'm guessing the same years as the SBC
Crossfire intake, 82-84. I know that with the Crossfire, GM had to do that
because they could not get the twin TBI setup to pass emissions.
Why such small ports for the BBC? For fuel economy, I assume?



an engines Torque peak is almost always very closely related to the point in the rpm curve where the most effective/efficient cylinder fill, cylinder fill is related to both intake port cross sectional area and exhaust scavenging,efficiency, and is limited by port stall, and cam duration in relation to displacement, compression and valve train stability, ...all factors are easily calculated
links below


useful RELATED INFO you might want to read

found this gasket over at summit..
using the correct head gasket too match the heads and cylinder heads your using on any big block chevy engine, is critical to prevent coolant loss, and maintain proper cooling
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,IF you forgot to use thread sealant on the head bolt threads, why, not try to eliminate one potential area of concern, not pull each head bolt one at a time and clean its threads dip the clean bolt in the can of sealant and reinstall and re-tighten the individual bolt to the required torque, before removing the next bolt, I've done this in the past when guys failed too seal the bolt threads and its worked and there was no head gasket issues later, the only thing you have to loose by trying this is the cost of a can of thread sealant and an hour or two of your time, and of course you'll more than likely need to re-adjust valves as the rockers will need to be removed at some point in the process.
you,ll want to place a head gasket you,ll use on the heads and mark the area inside the opening as the only areas you can change,
(notice the gasket fire ring is NOT a perfect circle like many people assume)
ideally you,ll want to un-shroud the valves while opening up the combustion chamber volume, but not extend the combustion chamber past the front edge of the gasket fire ring as that usually causes gasket failure

laying a head gasket on the head and use machinist blue dye to show the areas inside the gasket fire-ring



Brand Fel-Pro
Manufacturer's Part Number Q8180PT2
Part Type Head Gaskets
Product Line Fel-Pro Head Gaskets
Summit Racing Part Number FEL-8180PT-2

Bore (in) 4.370 in.
Bore (mm) 110.998mm
Gasket Material PermaTorqueMLS
Compressed Thickness (in) 0.039 in.
Compressed Volume (cc) 9.700cc
Lock Wire No
Quantity Sold individually.


TRICKFLOW ... 4294867081
1-330-630-1555 • 1-888-841-6556


Dart Machinery; 248/362-1188;

toll free: 877-892-8844
tel: 661-257-8124

Patriot Performance
Patriot Performance; 888/462-8276;


Toll Free: 877-776-4323
Local: 901-259-1134

EDELBROCK ... main.shtml
Edelbrock; 310/781-2222;

BMP (world products)
Tel: 631-737-0372
Fax: 631-737-0467





According to summits apps page

The gasket your have fits

Engine Type V8
Liter 6.5
CID 396
Engine Size 6.5L/396
Beginning Year 1966
Ending Year 1970
Engine Family Chevy big block Mark IV

Engine Type V8
Liter 6.6
CID 402
Engine Size 6.6L/402
Beginning Year 1970
Ending Year 1972
Engine Family Chevy big block Mark IV

Engine Type V8
Liter 7.4
CID 454
Engine Size 7.4L/454
Beginning Year 1970
Ending Year 1990
Engine Family Chevy big block Mark IV

it may be the result of a crack in the head or block or just an intake or head gasket leaking, issue, as stated change oil and filter ,
and if the problem returns you darn sure better track down the source before repairs get exponentially more expensive
some cracks won,t leak until the engine heat of the engine thats been running for awhile expands the metal.
if its not up too operating temp, theres no leak.
its not un-common for intake gaskets to leak coolant,
into the lifter gallery if they were not correctly installed or damaged, or intake manifolds to leak coolant,
if the coolant passages are corroded or improperly machined,
or too find coolant leaks if the wrong head gaskets were used.

IF you want max performance youll need decent hood clearance,and direct port EFI, to allow intake runners with a direct path from throttle body to intake valve in a strait line


Coolant Routing Mk IV/Gen 5/Gen 6
There 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'd assume the intake gaskets are the source until proven otherwise.
but be aware that miss matched head gaskets, to the heads and block combo in use, can cause several issues

don,t assume the worst, just logically and step by step track down and correct the issue using FACTS.
The Gen V was first installed in the 1991 year models.
The earliest casting I've decoded was a very late (Nov/Dec?) 1989 date.

The Gen VI was first installed in the 1996 year models.

The cams for the Mark IV and Gen V are interchangable for flat tappet lifters.
The Gen VI where the first equiped with Roller Lifters, but the main difference is the machined flats on the lifter bores of this block - you can still install an earlier cam without rollers.
The cam retainer plate holes are verticle on a Gen V~VI, rotated 90deg from the Mark IV's horizontal orientation.
The '91 on trucks with Gen V's had manual transmissions and use a bracket for the pivot, the later medium duty trucks have a hydraulic clutch.
The Gen blocks use longer main cap bolts than the Mark blocks.
The crank on the Gen engines uses one long key in the keyway slot for the cam drive gear and the damper - the Mark cranks have two short keyway slots and two seperate keys, one for the cam gear one for the damper.
As he stated, Gen cranks are one-piece seal, Mark are two-piece.
The Flex plates are interchangeable - but Flywheels, for truck and marine applications, are not interchangeable on Mark and Gen engines.


a couple known dependable engine builders
Last edited by a moderator:


The Grumpy Grease Monkey mechanical engineer.
Staff member

Big-Block Heads Shootout - The Big O Vs. The Big R
Oval ports and rectangular port heads
Richard Holdener Jul 18, 2012 1 Comment(s)
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Two issues back, we subjected a 468-inch big-block Chevy to a variety of different oval-port cylinder heads, ranging from stock peanut-port-style heads to full CNC-ported versions (see “The Big O”). In that story, we attempted to dispel the myth that any powerful big-block combination must include rectangular-port cylinder heads. Equipped with the right oval-port heads, the 468 easily exceeded 600 hp on the engine dyno. Most of the oval-port heads tested in part 1 offered airflow that would support another 100 hp on the right combination.

Contrary to popular opinion, our combination was limiting the potential of the oval-port cylinder heads, not the other way around. It is true that all of the factory performance big-blocks sported rectangular-port heads back in the day, but much has changed since the first muscle car era. Not only does a good set of aftermarket oval-port heads outflow the factory rec-port stuff, it does so with reduced port volume. Big, lazy ports are ideally suited for neither performance nor street use, while smaller, efficient ports offer the best of both worlds. Nowhere was this more evident than in the fact that a couple of manufacturers chose to supply oval-port heads once again on this larger (and more powerful) 496 test engine.

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A common stroker displacement, our 496 was the result of combining a 0.060-inch overbore with a 4.25-inch stroker crank. Our BBC rotating assembly came from the experts at Scat Enterprises. The BBC combination featured a 4340 forged steel crank combined with a set of matching 6.385-inch, I-beam rods. We chose a Scat crankshaft design specifically for our late-model, one-piece, four-bolt, Gen-6 block. The Scat crank and rods were combined with a set of forged pistons from JE. Offered as part of their SRP line up, the JE Pistons featured 18cc domes to produce a static compression ratio of 10.0:1 with typical 120cc combustion chambers.

The short-block was built not to maximize power production, but rather to demonstrate what is possible for street use in a performance driver. We wanted all of our testing to be run on pump gas, so we kept the static compression at a reasonable level. L&R Automotive was responsible for machining and balancing of the combination, while Total Seal came through with a set of performance rings to ensure proper sealing.

The displacement ensured that our 496 would be more powerful than the 468 used in part 1, but we hedged our bets with the installation of a wilder cam profile as well. Balancing the street/performance theme, we chose a small solid roller profile from Comp Cams. The 300BR-14 offered 0.652 lift, a 255/262 duration split and 114-degree LSA. To work in the Gen-6 block, the cam was teamed with a set of 0.300-tall solid roller lifters and a double roller timing chain.

Since the cam and timing chain were designed for a Gen-4 block, it was necessary to eliminate the factory cam retaining plate in favor of a traditional cam button. The swap also required the use of a custom front cover (PN217) from Comp Cams to provide the necessary room for the double-roller chain (factory Gen-6 covers must be run with a single-roller chain).

Finishing touches on the test mill included an Edelbrock Victor Jr. 454-R intake, a Holley 950 HP carb and SFI-approved, neutral damper from Procomp Electronics.

Prior to running the test engine, all of the heads were treated to flow bench testing to correlate the flow potential to the power gains. In truth, heads like the Brodix BB-3 Xtra O offered over 400 cfm--enough to support more than 800 hp. We were just scratching the surface or their potential with our 496 street/strip combination. After bench testing, we subjected the heads to port and chamber volume measurements. Since the compression ration is a function of the chamber volume, chamber size has a significant effect on the power curve (to the tune of 3-4 percent per point). Measurements indicated that our test heads varied greatly, from a low of 107cc to a high of 123cc. Bear this in mind when viewing the power numbers.

It is again worth mentioning that though this was originally to be a rec-port-only head test (to follow the oval-ports tested in part 1), some of the manufacturers supplied oval-port heads for this 496. Don't look down you noses at oval-port heads, as testing from both stories suggests that if anything, oval is the new square.

Test 1: Stock GM 088 Iron

Prior to running any of the aftermarket heads we had to establish a baseline by running the stockers. We chose a set of 088 castings that featured 316cc intake ports, 121cc exhaust ports and 123cc combustion chambers. The airflow data suggested that the stock iron heads would support over 650 hp, but on this 496, the heads managed to produce peak numbers of 630 hp at 6,600 rpm and 577 lb-ft of torque at 5,300 rpm. While 630 hp would make a serious street motor, we would see that the right head choice on this application would add nearly 100 hp to that total.

  • GM rectangular port castings
  • Retail Price-NA
  • Intake Valve Size-2.19
  • Exhaust Valve Size-1.88
  • Intake Port Vol-316 cc
  • Exhaust Port-121 cc
  • Chamber Volume-123 cc
  • Peak Power- 630 @ 6,600 rpm
  • Peak Torque- 577 lb-ft @ 5,300 rpm
  • Avg HP (3,500-6,500)-532.4
  • Avg TQ (3,500-6,500)- 560.5 lb-
  • TQ @ 4,000 RPM - 562.7lb-ft
Flow Data: CFM @ 28-ins
Stock 088
Lift In Ex
0.050 32 27
0.100 77 56
0.200 144 112
0.300 206 142
0.400 245 166
0.500 289 188
0.600 320 192
0.700 334 197
0.800 335 201

Test 2: Summit Racing Iron

Many would dismiss the iron heads simply for the weight savings, but don't count them out, especially when you consider the price and performance. These rectangular port iron heads from Summit Racing offered surprising bang for the buck. The Summit Racing head upgrade improved the power output of the 496 from 630 hp and 577 lb-ft to 688 hp and 607 lb-ft. This was all the more impressive considering the fact that the heads cost just $750 bucks each, assembled. Toss in the fact that the Summit heads flow only marginally better than the stock heads and share the same combustion chamber volume. If you are looking for iron heads on a budget, look no further than Summit Racing.

  • Retail Price-$749
  • Intake Valve Size-2.25
  • Exhaust Valve Size-1.88
  • Intake Port Vol-309 cc
  • Exhaust Port Vol-127 cc
  • Chamber Volume-122 cc
  • Peak Power- 688 hp @ 6,600 rpm
  • Peak Torque- 607 lb-ft @ 5,400 rpm
  • Ave HP (3,500-6,500)-555.5
  • Ave TQ (3,500-6,500)-582.1
  • TQ @ 4,000 RPM-563.3 lb-ft

Summit Racing Iron
Flow Data: CFM @ 28-ins
Lift In Ex
.050 34 34
.100 69 69
.200 146 109
.300 204 155
.400 264 192
.500 309 223
.600 340 246
.700 323 262
.800 330 273

Test 3: Procomp Electronics Rec-Port CNC

The aluminum heads from Procomp Electronics combined the largest port volume and (nearly) peak flow numbers with the lowest retail cost. The intake port volume measured a sizable 369cc, while the exhaust checked in at 157cc. This head configuration would be much more at home on a larger displacement, higher horsepower application, but how can you argue with aluminum BBC heads that flowed over 400 cfm for around $600? Equipped with the Procomp heads, the BBC stroker pumped out 690 hp and 600 lb-ft of torque. We suspect the large port volume and sizable combustion chamber hurt torque and power on this application, as many of the other heads featured smaller chambers and port volumes. We'd like to see this head strut its stuff on a high-compression 572, but for our 496, it was likely just too big.

  • Retail Price-$625
  • Intake Valve Size-2.30
  • Exhaust Valve Size-1.88
  • Intake Port Vol-369 cc
  • Exhaust Port Vol-157 cc
  • Chamber Volume-123 cc
  • Peak Power- 690 hp @ 6,300 rpm
  • Peak Torque- 600 lb-ft @ 5,500 rpm
  • Ave HP (3,500-6,500)-554.2 hp
  • Ave TQ (3,500-6,500)- 581 lb-ft
  • Tq @ 4,000 RPM-568.3 lb-ft

Procomp Electronics BBC Rec-Port CNC
Flow Data: CFM @ 28-ins
Lift In Ex
.050 35 31
.100 70 67
.200 152 132
.300 234 175
.400 294 206
.500 336 231
.600 364 251
.700 389 267
.800 403 279

Test 4: Trick Flow Specialties PowerPort 360 Heads

Like the Procomp heads, the PowerPort 360s from Trick Flow Specialties were probably a tad on the big side for the 496. With intake ports that measured 357cc, the impressive PowerPorts would be more at home on a big-block exceeding 500 cubic inches. With peak intake flow numbers of 384 cfm, the heads we capable of supporting over 750 hp, but on our 496 manage 691 hp and 603 lb-ft of torque. The PowerPort heads shared the large (122cc) combustion chamber volume of the stock heads and came in at a cost-effective $1,229 (through Summit Racing).

  • Retail Price-$1229
  • Intake Valve Size-2.30
  • Exhaust Valve Size-1.88
  • Intake Port Vol-357 cc
  • Exhaust Port Vol-134 cc
  • Chamber Volume-122 cc
  • Peak Power- 691 hp @ 6,400 rpm
  • Peak Torque- 603 lb-ft @ 5,400 rpm
  • Ave HP (3,500-6,500)-555.3
  • Ave TQ (3,500-6,500)- 581.9 lb-ft
  • TQ @ 4,000 RPM-562.3 lb-ft

Trick Flow Specialties PowerPort 360 head
Flow Data: CFM @ 28-ins
Lift In Ex
.050 35 30
.100 72 61
.200 148 125
.300 217 168
.400 275 198
.500 325 227
.600 360 246
.700 376 261
.800 384 273

Test 5: Brodix BB-3 Xtra 332

The new Brodix BB-3 Xtra 332 heads were not quite a rec-port head nor were they a conventional oval (or peanut) port head. They were somewhere in the middle, more like a rectangular-port with rounded corners. In truth, use of the 454-R (rec-port) intake may have hindered the power potential of the Brodix heads more than others due to the port mismatch. One thing for certain is that the Brodix heads topped all comers in terms of airflow with peak numbers of 409 cfm. Capable of supporting over 800 hp, our 496 produced 705 hp and 624 lb-ft of torque. We would love to port-match an intake to these heads in an attempt to translate all that airflow potential into power.

  • Retail Price-$1840
  • Intake Valve Size-2.30
  • Exhaust Valve Size-1.88
  • Intake Port Vol-335 cc
  • Exhaust Port Vol-133 cc
  • Chamber Volume-115 cc
  • Peak Power- 705 hp @ 6,400 rpm
  • Peak Torque- 624 lb-ft @ 5,200 rpm
  • Ave HP (3,500-6,500)-574.6
  • Ave TQ (3,500-6,500)- 602.7 lb-ft
  • TQ @ 4,000 RPM-585.7 lb-ft
Brodix BB-3 Xtra 33
Flow Data: CFM @ 28-ins
Lift In Ex
.050 33 31
.100 66 69
.200 147 120
.300 211 173
.400 273 221
.500 333 256
.600 380 277
.700 409 286
.800 403 296

Test 6: Dart Pro 1 335

The Pro 1 name from Dart has always meant power and this test illustrates that the name still carries some weight. For our street/strip 496 BBC, Dart supplied a set of its CNC-ported 335 heads. With flow numbers that reached nearly 400 cfm, the Dart Pro 1s were another set of 800-hp heads in search of a motor. The Dart Pro 1 heads featured rolled valve angles and raised exhaust ports to improve flow and power, but remained compatible with stock accessories. Run on the dyno, the big-block produced 717 hp and 619 lb-ft of torque. Equipped with a smaller chamber shared by the AFR and Edelbrock heads, the Dart would likely be right in the hunt for maximum power.

  • Retail Price-$2021
  • Intake Valve Size-2.30
  • Exhaust Valve Size-1.88
  • Intake Port Vol-303 cc
  • Exhaust Port Vol-137 cc
  • Chamber Volume-122 cc
  • Peak Power- 717 hp @ 6,500 rpm
  • Peak Torque- 619 lb-ft @ 5,600 rpm
  • Ave HP (3,500-6,500)-568.0
  • Ave TQ (3,500-6,500)-594.3 lb-ft
  • TQ @ 4,000 RPM-572.5 lb-ft

Dart Pro 1 335
Flow Data: CFM @ 28-ins
Lift In Ex
.050 34 29
.100 69 61
.200 148 125
.300 228 181
.400 294 219
.500 336 249
.600 376 271
.700 398 281
.800 399 289

Test 7: Edelbrock E-CNC 355

Edelbrock has stepped up in a big way recently with new performance offerings and these E-CNC 335 heads are a perfect example. Proudly made in the USA, the E-CNC heads offered plenty of flow, peaking at 391 cfm on the intake and 285 cfm on the exhaust. Sporting the smallest combustion chamber of the bunch at 107cc, the Edelbrock heads produced the highest static compression ratio. Naturally this helped power, allowing the E-CNC heads to produce 723 hp and 627 lb-ft of torque.

  • Retail Price-$1,630 (required spring upgrade)
  • Intake Valve Size-2.30
  • Exhaust Valve Size-1.88
  • Intake Port Vol-353cc
  • Chamber Volume-107 cc
  • Exhaust Port Vol-135 cc
  • Peak Power- 723 hp @ 6,500 rpm
  • Peak Torque- 627 lb-ft @ 5,600 rpm
  • Ave HP (3,500-6,500)-573.5 hp
  • Ave TQ (3,500-6,500)- 599.9 lb-ft
  • TQ @ 4,000 RPM-574.0 lb-ft

Edelbrock E-CNC 355
Flow Data: CFM @ 28-ins
Lift In Ex
.050 33 29
.100 73 61
.200 148 132
.300 224 185
.400 283 226
.500 334 252
.600 364 270
.700 385 278
.800 381 285

Test 8 AFR Magnum 300 Oval

It takes more than just big flow numbers to make power, and these Airflow Research heads proved that. In fact, when asked to supply rec-port heads for this test, they opted to instead send over a set of oval-port heads. It new 300cc Magnum heads did not offer the highest peak flow numbers, topping out at 383 cfm (at .650 lift), but when combined with exceptional mid-lift flow and an efficient chamber design, the results were enough impressive. Power production is all about the combination of components working together and on this 496, the AFR Magnum 300 heads proved to be the optimum combination by producing 729 hp and 639 lb-ft of torque.

  • Retail Price-$1,559
  • Intake Valve Size-2.30
  • Exhaust Valve Size-1.88
  • Intake Port Vol-300 cc
  • Exhaust Port Vol-123 cc
  • Chamber Volume-110 cc
  • Peak Power- 729 hp @ 6,500 rpm
  • Peak Torque- 639 lb-ft @ 5,400 rpm
  • Avg HP (3,500-6,500)-584.1
  • Avg TQ (3,500-6,500)-611.4 lb-ft
  • TQ @ 4,000 rpm-587.0 lb-ft

AFR Magnum 300 Oval
Flow Data: CFM @ 28-ins
Lift In Ex
.050 34 32
.100 74 62
.200 153 126
.300 233 198
.400 296 237
.500 345 263
.600 377 277
.700 371 288
.800 365 296

21 The combustion chamber of each cylinder head tested was measured.


The Grumpy Grease Monkey mechanical engineer.
Staff member
I frequently hear guys tell me that the rectangular port BBC heads are the wrong choice for a street driven cars engine.
as I've stated dozens of times, you should generally design a street performance engine to maximize its torque curve in the rpm range its going to be driven at most of the time.
Customer wanted to maintain power brakes but wanted 500+ HP with decent street manners. Also since he is in CA it needed to run on 91 octane. The customer and his engine builder were very happy
heres a dyno chart from a 489 stroked 427 engine using a moderate duration hydraulic roller cam,
factory rectangle port heads and a dual plane intake, that not only makes impressive power but does it over a broad rpm range,
the idea was to have an engine that would have enough plenum vacuum to run power brakes,
but still produce impressive power over a broad rpm range ,
notice the fuel air ratio is too rich on this dyno pull,the mild 229/241 duration on the roller cam and dual plane intake, and 750 cfm Holley carburetor, being used. on the rectangular port heads.
if it was no richer than about 12.6:1 power would improve further.




(Words and photos by Scott Liggett) – We know many Bang Shifters are not made out of money. We are in that crowd ourselves. Any way we can save money on our project cars allows us to have a better car or truck. The easiest place to save money using our time and sweat instead of paying shop labor rates. One place many people often over look is the assembly part of rebuilding an engine.

Sure, there are few that have access to the tools necessary to do machine work on our engines, but putting together an engine doesn’t require fancy tools. A good torque wrench is about the only fancy tool that we needed putting together a 454 we recently had machined for a rebuild. Since we were getting estimates up to $500 from machine shops to assemble our engine, we decided that we save that money by taking the time to do it ourselves. That is just putting the new parts and machined block, crank and rods back together.

Yes, we were a bit apprehensive to do it. Engines are not cheap to get built these days. That can scare many people away from attempting this kind of work. But, after talking to some friends and our machine shops, we decided to go for it.

Truth be told, this is our second time assembling this 454 after machine work. But, the reasoning for this had nothing to do with the machine work done, or assembly job. We had two things that had us pulling the engine again after only 10,000 miles. First, we had constant lifter noise after the engine warmed up. Second,was piston slap from only doing a dingle ball hone with the original pistons with new rings and bearings. All the lifters failed a bleed down test and the pistons had too much clearance after the home honing job. This time we bought new pistons and had the block completely machined top to bottom with a .030 over bore. The rotating assembly had to be balanced for use with the new pistons.

You want to work in as clean as space as possible to avoid debris getting into your fresh engine. We were working in Scott’s one car garage at his house, which is pretty clean. We kept the engine covered by old, but clean towels in between days we were working on the engine.

This is how we received our 454 block back from the machine shop. The guys over at BluePrint Engines did the work for Scott and the block came back looking like a brand new casting, not like a 45 year old block. In case it isn’t obvious, the first thing to do is to get it on an engine stand. We got our from Harbor Freight, but this one is the big dog. A fully dressed 454 weighs near 700 lbs. They also replaced all the freeze and galley plugs for us.

After taping off the areas we didn’t want painted, we shot the engine in Chevy Orange. We were told not to paint in the oil filter housing, so we took some time to clean that up later in the build.

Before doing any assembly, we decided to see if our factory windage tray would work with the Milodon 7 quart oil pan and Melling high volume oil pump we are using. We also decided to upgrade to ARP main studs instead reusing the original main bolts for better support for the crank. The studs have provisions for the windage tray.

Even though the Milodon pan has these dimples to make room for the studs, we had to dimple them a bit more so the pan would sit flush on the block.

BluePrint Engines did the crank turning and balancing for us as well. The crank was standard when we took it to them, but polishing did not get all the scratches out of the bearing surfaces, so we had it turned .010/.010. They balance all their rotating assemblies below 2 grams, but ours came out .41 grams on the front and .89 grams on the back. We first laid in the block sides of the main bearings and carefully laid the crank in the block without any assembly lube at this point. Forged big block cranks weigh in excess of 60 pounds, so if you can get help to set it in the block, do so. Dropping it on your bearings, or your foot, would not be good.

Next, we cleaned the main caps with Brakleen and a lint free rag before installing their half of the main bearings. Even though the block was thoroughly washed after machining, their was still some dirt after sitting around for two weeks before getting to work on it. The rear main seal is not needed at this point.

We got some Plastigauge from the local parts store to double check bearing clearances. Your machine shop should have done this during the machining process with their measurements. You are just making sure. Taking your time and being anal during engine assembly is a good thing. After laying the piece of waxy, plastic string across the bearing surface on the mains, you place the main caps on and torque them down to manufacture specs. In the case of our 454, it was 105 ft lbs.

Next, remove the main caps and check the measurements on the Plastigauge’s paper cover. Our Chevy Factory Overhaul Manual says that the main should have between .001 and .003 clearance. All of our mains had .015 readings. This is only approximately, but you are being sure of what you got before you have the engine together and running. The alternative is finding bearing material in your oil filter after a few miles. Not a good day. Repeat this process on all of the main caps and bearings.

Remove the crank from the block, then get out your engine assembly lube and liberally cover the main bearings. Then, you need get out the rear main seal from your engine gasket set. Fel-Pro includes instructions on which way it is suppose be installed to keep it from leaking all over your driveway.

Some people say you should install the rear main seal halves offset slightly for better leak protection. Others don’t. We did.. We did add a little bit of RightStuff sealant on the seal ends for added security.

Now your crank is done. Time to move on the connecting rods and pistons. We used the same plastigauge on each of the rod bearings to check their clearances as well.

For the purpose of checking the bearing clearances with the pistons already installed on the rods, we did this before installing the rings on the pistons. This made sliding them in and out of the bores much easier. The rods were stamped with their numbers when Scott took the engine apart before machining, but he wrote big numbers on the end caps cause he is slowly going blind like all middle aged men. The machine shop added those colored paint dabs as part of their checks and rechecks. They mark the side of the rod that has the rod bearing tabs. The tabs should face towards the outer part of the block.

Torque the rod bolts to their recommended specs. Before removing the rod caps and checking the clearances with the plastigauge you used, check the side clearances on the rods. We checked between the rod pairs and between the rods and the crank sides. On our 454, those clearances should be between .015″ and .021″. Bearing clearances on our 454 is the same as mains, .001″-.003″.

After checking the rod clearances were all good, we moved on to installing the rings on the pistons. Even if you buy rings that are supposed to be pregapped, we suggest you check the clearances anyways. Remember what we said about being thoroughly anal? Our rings came with our piston set from Keith Black. They are moly rings, but we had to gap them. It is tedious, but necessary. Too tight of clearances and you will break them and the ring lands on the pistons. Too loose and you can have oil usage problems and lack of power. We wanted to get consistent measurements, so we always made sure they were the same distance down in the bores each time.

Using a feeler gauge find the clearance on the ring. The measurement will depend on the type of rings you are using and the intended purpose of your engine. The use of nitrous and boosted engines need more clearance for the added cylinder pressure and heat. We wanted .021″ on the top ring, and .024″ on the second ring.

Our rings needed a bit of filing. here are ring gapping tools available from many companies, but we put a metal file in the bench vise and gently ground them a bit. Do a little bit at a time. Don’t get in a hurry. It’s better to go back to the file a few times, then over gap your rings.

Once all 16 rings are gapped, they need to be installed on the pistons. Certain types of rings are reversible. Ones that are not often have a dot to which side is the top. Keith Black’s instructions said not spiral them onto the pistons. This means we needed to spread the two ends apart in order to get the rings on the pistons. There are many inexpensive tools for safely doing this. We should have gotten one ourselves as we got impatient and broke one of the rings trying to install it. The oil rings are the easiest to install and are usually three pieces.

Since ring sets don’t come with spares, we had to order another set. We were able to get another set of the same style and material from another brand, but it will work.

Clock the rings 180* apart before moving on to installing the pistons and rods in the engine for the last time.

Now that there are piston rings on your pistons, getting them into the block is a little more work. So not damage the bearing surfaces on your crank, cover the rod bolts with rubber hoses or specific boots so not to scratch crank. We just used 3/8″ fuel line.

Now, it’s time to install your rods and pistons for the last time. You will need a ring compressor. There are fancy, size specific ones available. We just used this $18.00 one we got at Napa. Set the rod into the bore, then tap the compressor flush with the deck surface of the block. Be sure the valve reliefs in the pistons are oriented in the correct direction.

We used the rubber handle of a ballpeen hammer to tap the piston down into the bore. A dead blow, or a specific dead blow piston driving tool will work as well. Just do not use anything metal against the piston face. That would be bad.

With this type of ring compressor tool, you do need to stop a couple of times during the piston installation to be sure the compressor stays flush with the deck surface. If the piston ring slips out, you will be starting over.

Use the engine assembly lube on the rod bearing halves just like the main bearings. When you get the piston driven down to where the rod meets the crank throw, put the rod cap on the rod and tighten the bolts down to recommended specs. Our ARP rod bolts were torqued to 50 ft lbs.

You will need to install your oil pump next. Don’t forget the oil pump pickup screen as well. We are using a Melling high volume pump and a pickup screen for use with a 7 quart oil pan. This pickup screen is pretty much dummy proof in it’s installation. We still checked for it’s clearance to the bottom of the oil pan. Before installing the oil pump, make sure you install the oil pump drive shaft first, or the day you fire up your engine will not be a good day. The oil pump’s bolt gets torqued to 60 ft lbs on our 454. The rotating assembly installation is complete.

We took some extra time to install our factory windage tray for better oil control and a few more horsepower. Our ARP stud kit included the four longer studs for its use. Be sure to check the rod clearance under the windage tray. Rotating parts need at least .060″ clearance.

Flip the engine back over for the camshaft installation. Apply liberal amounts of moly lube to the camshaft lobes and bearing surfaces. We only add the moly lube to four lobes and a bearing surface at a time, then install the cam up to that point. Then add some more to the next set of four. The keeps your hands cleaner and it easier to install. We used a 5/16″ x 6 inch long bolt in the front of the cam for more leverage. Or, you can buy a cam handle. We’re cheap.

We used this cam moly lube we got from Isky. This tub has been used on five or six cams and we still have plenty left.

The last thing to do is install the timing chain. First, drive the crank gear on the crank with the round dot on the crank key way and the dot pointing straight up. The cam gear goes on with the dot pointing straight down. This Cloyes timing set has a three way set up for advancing, or retarding the cam 4*. We installed ours straight up.

That’s it for the short block. The cam’s lifters will go in with the pushrods and valvetrain. It wasn’t all that hard, was it? We did this over a weekend.

btw the multi part timing chain covers that allow a faster cam change are available at a not much increased price for some 1966-1990 BBC applications,
obviously youll want to ask questions and get the correct matched components for your application.
and sbc




sbctimcovc.jpg port size headers head flow required head flow rpm stress limitations

SOME ROLLER ROCKERS CAN AND DO BIND ON ROCKER STUDS, or rocker adjustment nuts, youll need to check carefully

some roller rocker too retainer combo clearance issues cause problems easily solved with beehive springs and smaller retainer diameters



  • bbcbolt5.png
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