interesting big block chevy 454 cam dyno test


Staff member ... ifold.html
while reading this keep in mind the AFR aluminum CNC ported heads
are EASILY worth 80 plus hp over what a similar engine would produce using factory oval port production cylinder heads,
and the edelbrock , air gap, oval port, intakes
easily worth 25 hp over the stock intake.
the roller rockers an easy 20 more hp over the stock stamped rockers ... /overview/
Id also point out that the 265cc heads are a bit small for the most aggressive cam used to produce maximum power,
the 290cc would be a better match in an engine running that cam
The Test

To get a handle on how this all plays out in a real-world engine combination we decided to hit the dyno with three hydraulic roller grinds from Crane Cams. Our test engine is nothing more exotic than a production big-block Chevy 454. The engine was prepped by boring it out for a set of short-dome JE pistons to bring the compression ratio over the 10:1 mark, adding a set of Scat H-beam rods for durability, while freshening the stock Chevy crank. Up top, we went with a set of deceptively capable oval-port AFR cylinder heads. The heads feature a modest port volume of just 265 cc, but these fully CNC-ported castings have the airflow to support healthy output. Supplying the air is an Edelbrock Performer RPM Air-Gap intake manifold fed by a Holley 950 Ultra HP 4150-series carburetor. In short, our engine is the type of budget performance Chevy big-block you’ll find on streets across the United States, based on production components and spiced up with aftermarket goodness where it counts.

With the popularity of hydraulic roller cams in today’s street builds, it made sense to select that cam configuration for our dyno session. The advantages of the juice roller include virtually eliminating unexpected cam lobe/lifter failure in initial running, and the ability to add enough valvespring reliably to spin up some high-rpm power. The roller profiles offer much more lift than we would expect to run reliably on a flat-tappet combination, giving the potential for serious power production. To complement the cam, we opted for a set of Crane’s standard retrofit hydraulic roller lifters, PN 13532-16, along with Crane’s excellent 13763TR-16 aluminum-bodied roller rocker arms. The cylinder heads were ordered with AFR’s excellent hydraulic roller spring combination, so we were covered there.
Cammed For Power

To best illustrate the varied characteristics affected by cam size, it made sense to step the specifications up fairly substantially between the cams. We opted for sizable jumps of 12 and 14 degrees duration as measured at .050-inch lift. Our baseline cam, with 222/230 degrees duration at .050 would be considered a baby cam by performance veterans, but with lift of .576/.598 inch, it moves the valves with authority, and with a healthy lope can in no way be construed as a stock cam. Testing showed that even this small stick has its big-boy pants on, taking our mild 454 combo up to 570 hp at 5,800 rpm, and pulling cleanly over 6,200 rpm.

That’s healthy power for a pump-gas street 454. What was more impressive came lower in the operating range, where the torque right off the hit at 3,000 rpm was 539 lb-ft, twisting strongly to a peak of 587 lb-ft from 3,900 to 4,100 rpm. Our small cam delivered the torque needed to launch heavy street metal, while dishing plenty of punch up top. While the duration specs would seem conservative, don’t be fooled, this unit definitely proved to be performance minded. The smallest of our trio of cams idled with a noticeable performance lope and registered a healthy 15 in-hg of vacuum at a 1,000-rpm idle.

Our next step in cam size moved up to 234/242 degrees duration at .050, a neighborhood that is popular with today’s street performance enthusiasts. We tore the engine down as it sat on the dyno for the cam change, retaining everything else exactly as it was in our previous combination. The upsized cam featured a significant jump in lift, shoving the valves to well over the .600-inch mark. We expected the increase in lift and duration to tap into more of the excellent high-lift airflow of the AFR heads, and bump top end power. The dyno numbers showed a textbook example of what is gained and what is lost as the cam timing is increased. Up top, we now recorded 599 hp at 6,100 rpm, gaining in both output and usable rpm, however, the bump of 12 hp up top shaved 8 lb-ft from peak torque, and shifted the torque peak higher up the rev range. This move in the torque curve was most noticeable in the lower end of the rev range, with substantial torque losses below 4,000 rpm. Idle lope was noticeably more pronounced and vacuum measured 12 in-hg at 1,000 rpm.

Our intermediate cam was clearly favoring the upper end of the rpm range, and at this level of cam duration a single-plane intake manifold would likely further complement the high-rpm power. To explore the effects of a change in manifold configuration, we swapped the intake to Edelbrock’s Victor Jr. 454-O, a single-plane designed for the oval-port heads. With no other changes to our test engine, the swap resulted in a classic example of a single-plane versus dual-plane comparison. Up top, we now recorded 609 hp from 6,000-6,200 rpm. With handily over 600 hp on tap, we definitely gained in bragging rights, but it came with a clear loss in torque at lower rpm. The point at which peak torque occurred moved up and moved peak torque rpm up by a surprising 900 rpm. The single-plane runner layout also resulted in a small penalty in idle vacuum, now recorded at 11.7 in-hg at 1,000 rpm.

Our final test configuration featured another large move up in camshaft specs, this time to 248/256 degrees duration at .050- and .630-inch lift, retaining the single-plane manifold from our previous test. Our big cam definitely made itself known with a raucous lope and just 7.0 in-hg of vacuum at 1,000 rpm. Following the pattern of our previous tests, the big stick once again traded torque downstairs for horsepower at the upper reaches of the tach. We now had an impressive 630 hp on tap at 6,400 rpm, with the combination pulling cleanly to a maximum of 6,700 rpm. Those numbers are pretty imposing for a pump-gas street 454!
Superflow The “bigger” intermediate cam exhibited exactly the change to the engine’s characteristics

The penalty here, as you might expect, is more torque skinned off the lower rpm range. Compared to our baseline combo we were down over 80 lb-ft at 3,000 rpm, although looking at torque from peak to peak the difference shrinks to just 10 lb-ft. As had been the case through each of our changes, the powerband moved up, trading bottom end output and idle quality for more all-out power. These compromises are the essence of what performance enthusiasts are faced with when making their camshaft decision. Our baseline cam delivered mountains of low-end grunt, and has the legs for excellent power up top. The ferocious idle of our big cam would definitely come with compromises in street driveability, but might just offer the boulevard presence and power curve you are after. With a serious converter and street tires, the torque lost down low would likely never even make itself known. When it comes to cams, one size doesn’t fit all, the right cam is tailored to your application and goals.




ignoring or skipping the links would be a big mistake

a couple known dependable engine builders
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I read recent that Pro engine builders are flow testing heads no longer just at 28" inches of water depression Grumpy.
Many are now using 56".
Some are using 100" or over.
To simulate closer to what's actually happening inside of a running engine.
Also been told many afternarket heads start getting turbulent inside of ports above 28".
A loud drumming sound is noticed and flow quits. Choked off.
Just intetesting.


Staff member
If you read enough internet posts you might get the erroneous idea that any and ALL big block chevy engines built for street/strip or performance use are almost always better off if they were to be built with the small to medium, 256cc-270cc oval port heads, and while theres some truth to that if you limit the engines displacement and use to those with restrictive exhausts, and intakes etc. thats certainly not a fact written in granite, especially if you take the time to think the combo thru and correctly match, displacement,cam timing,exhaust scavenging, intake manifold and header design.
stick a fairly high compression BIG BLOCK, from 454-540 cubic inches displacement, with the correct matched components, in a light weight car with a strong drive train and a sturdy frame and hold on tight!

Id also point out that OWNING , or running ,a speed shop or machine shop , or working at one may not mean you know squat about making an engine run to its full potential,
but it will generally mean your fully submerged in the process of learning, what works and sells or you'll eventually be out of business.
Ive dealt with several skilled machinists and welders, and dozens of
(speed shop employees that were skilled in their particular area of expertize that were all but clueless , in many areas of engine building ),
simply because they do not need to know or in some cases even care to learn about those areas.
you always need to do research on what your trying to do and recognize the fact that theres a ton of mis-information being tossed around on the internet and from other sources based on selling merchandise at a profit,or based on what might have worked on a totally dis-similar application, rather than what really works best, in some car similar to YOUR application.
guys who have a winning combo rarely want to give their competition all the FACTS about WHY their car is faster or why it continues to run well while the competitors constantly break down.
and performance magazines get paid big bucks to promote the sale of certain components , by manufacturers ,regardless of the real documented results of careful comparative testing.
one good example I know about is that many times you'll read about some engine combo and they may list a certain intake manifold or cylinder heads or a certain cam being used, they also fail to mention the fact that there may have had many additional hours of welding and port work done to those heads or that intake design, or ordered the cam on a much tighter 104 LSA vs the stock 112 LSA, and use it with a different rocker ratio,or conveniently omit the fact that you need some additional component work to get those parts to run efficiently like aftermarket valve train components like vascojet,valve springs,titanium retainers,or some expensive sodium filled exhaust valves, or they forget to mention the 2" titanium exhaust valve and 5 angle valve job on the big block turbo heads





CRANE Cams Master Catalog.pdf

ERSON erson catalog.pdf




If your building a tall deck block based BBC 496 stroker, youll generally want to build a tall deck, engine with longer connecting rods to take full advantage of the tall deck architecture
the deck heights .400 taller so youll generally want connecting rods that are longer on the 4.25", stroke , stroker crank
IVE GENERALLY USED SCAT CRANK ROTATING ASSEMBLIES WITH 7/16" ARP ROD BOLTS and 6.385" 0r 6.535" rods as they are longer to compensate for the .400 taller deck height, a call to SCAT will get you the correct part number for a kit forged and internally balanced rotating assembly kit Phone: 310 370 5501

Ive generally gone 6.535 with a 1.52 simply because the ring spacing and support clearances are better in my opinion

10.2 deck minus 1.52 compression height, minus 6.535 rods and 4.25/2= minus 2.125 stroke = .02 so the pistons going to stick above the deck .02 requiring a bit thicker .062 head gasket too get the .040-.042 quench Ill look to
achieve, of course if the blocks never been decked it may have the extra .02-.023 still there so measure before buying head gaskets and CC your heads

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

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.

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.

Victor Reinz part numbers 4918(right bank) and 4923 (left bank) are available for GM 7.4L (454 CID)



the tall deck block requires a longer reach distributor shaft thats about 0.28 longer thus the need for the adjustable collar on the distributor adding the extra reach to get the oil pump drive and drive gears to properly align and mesh.


be aware theres an oil supply passage in the lower block skirt, and coolant passages that extend quite low on the mark IV blocks so you can't just grind excessive rod clearance, for crank counter weights and large, longer stroke , stroker type crank's to the same extent you can get away with on the later MARK V and VI blocks, or the far better choice of a DART aftermarket block, so you'll need to be careful,doing clearance grinding,I would advise limiting stroke lengths to a 4.375" max, even in the tall deck truck MARK IV blocks, the later Mark V and VI blocks have that passage up near the cam tunnel

related info and YEAH! failing to read links or ignoring them can get expensive
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Staff member

notice that in the video they BRIEFLY mentioned changing BOTH THE OIL AND IGNITION WIRE between the base test and ignition wire test, the swap to a lighter viscosity synthetic oil could easily have accounted for 1/2 or more of the power gains, now I,m not saying the wire change did not help but Im suggesting it was not the lone factor involved



The Big Block Chevy is far from dead Grumpy.
Just wish I had more parts on hand to use on my 427 Tall Deck.
I know 1st hand how mean they are built Full tilt street.
All out Drag Race.
Only Pontiac 455- 600 Cubic Monsters can compete from GM Old School.


Big Tube Race headers easily available for Big Chevy like Pontiac V8.
Makes both Winners to me.


solid fixture here in the forum
been looking at prices for 79-81 trans ams thinking of some day building a big block car out of one. seem like a great plaform, wish there were more of them on the street... i really like those cars.


philly said:
been looking at prices for 79-81 trans ams thinking of some day building a big block car out of one. seem like a great plaform, wish there were more of them on the street... i really like those cars.
They have become valuable now too.
Formula Firebird almost same car without all spoilers.


solid fixture here in the forum
Strictly Attitude said:
easily transformed to a bandit car by changing the nose easy conversion

no way i want a 79-82 speifically because it doesnt have the bandit nose... i prefer the later bumpers and spoilers. if i could find another racaro t/a pace car that would be incredible. but i would have to either get rich or those cars magically devalue back into my price range