[scott70]

I see different configurations of cubic inch.heads, intake,cams and am surprised at some of the different hp/trq. outputs. Why is it sometimes that I see a 455 /400 with aluminum heads ,roller cam ,aluminum intake make the same hp (or very close) and torque to some engines that have cast-iron heads, iron intakes , flat tappet cams and quadrajets. Yes usually the cast-iron heads are ported ,usually only between 250 and 270 CFM. Over the last few years I've seen people post dynos of there engine that have aluminum heads ,roller cammed,etc that make a little over 500 horse did 550 trq. Which is easily done with a iron headed engine. Just surprised at some of the numbers I see and I expect quite a bit more when I see a aluminum,heads roller cam and a nice intake

[pastry_chef]

Originally Posted by scott70

Just surprised at some of the numbers I see and I expect quite a bit more when I see a aluminum,heads roller cam and a nice intake

Examples?

[RocktimusPryme]

I would bet that the flat tappet cams are often notably more radical. My roller is pretty tame.

[slowbird]

Dyno difference a nd builder difference.
Give two builders the same parts and the end result can be vastly different.
Put the same engine on two different dyno's and results will very

[72LuxuryLeMansLa.]

IMHO Many that use aluminum do it because for the same money you would spend on nice ported iron head you can get the same flow with out the box aluminum. You are also buying plenty of headroom for future upgrades if you want to port the aluminum whereas the iron is maxed out. Add a roller cam and you have the same power output as a flat cam but with smoother idle/low speed performance and little chance of cam failure. A man could build an engine with the desire to only make 400hp with aluminum heads and roller cam. Doesn't always need to be max effort.

[P@blo]

Since this is in the street section; port velocity is an important consideration when choosing cylinder heads. The factory ported iron head is the only option with modest runner volumes and if a iron head that flowed at 270 cm became available they would fly out the door.

Jim Hand ran factory stuff quite successfully so skin the cat how you like

[Steve C.]

“Many feel the 215cc intake port of our Performer RPM is too large for the street, but we’ve found that the long connecting rod and big crankshaft throw associated with the Pontiac V-8 tend to make them less sensitive to port volume. The RPM is a great head for street engines, and I pushed for a large intake port when developing the Performer D-port-one much like that used in our Performer RPM.”

The First Look At Edelbrock's New Performer D-Port Casting For Pontiac V-8s

https://www.hotrod.com/articles/hppp...ylinder-heads/


Many in the Pontiac community do not have the small runner volume syndrome



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[scott70]

Originally Posted by pastry_chef

Examples?

In another thread where somebody was asking which cam cliff was talking about a 428 build which made decent power but the size of the roller cam and heads it was just okay. That thread was just another reminder to me of others I've seen. There are many other examples that I've seen here and other sites over the years. Yes there's room to grow with the aluminum heads but 500/550 isn't a problem for iron stuff and alot of times that's what they're getting with aluminum stuff that should be well outperforming imo. I've seen articles with aluminum heads and roller cams and then run 12 's. I tell my self that's it for the money? I'm talking mildish street builds not race engines. Just my thoughts...I could be way off base here but I then see just ok et' s that a not all out , decent iron, flat cam can do. I do understand the convience of bolt on but I'm talking about is after it's all said and done, there are many iron,flat builds the HP/trq the same and perform the same as higher priced aluminum, roller builds that I think should be outperforming the iron stuff. And no I'm not talking radical flat cams either.

[RocktimusPryme]

Like was said earlier, I don’t think it costs as much extra as you think for the heads. I considered the ported iron route, but then realized I was t rally saving any money. I ended up buying a set of used iron heads and had them gone through/ported.

The roller on the other hand is way more expensive.

[pastry_chef]

Originally Posted by scott70

In another thread where somebody was asking which cam cliff was talking about a 428 build which made decent power but the size of the roller cam and heads it was just okay. That thread was just another reminder to me of others I've seen. There are many other examples that I've seen here and other sites over the years.

When you see flowed aluminum heads and a roller cam making "around" 500 HP the intake is not getting it done. Swap over to a T2 and watch the power jump.

[Steve C.]

Example, one of many....

"We decided to do some intake manifold comparison testing on a 474ci engine running a set of our 290cfm CNC ported KRE D-port heads with 10.2 to 1 compression on 91 octane fuel with a 236/245 duration hyd. roller cam."

Intake Manifold Dyno Test :

http://www.sdperformance.com/newsStory.php?newsID=44


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[Steve C.]

About 17 years ago in Pontiac Enthusiast Magazine within a brief overview about different Pontiac intake manifolds Pete McCarthy said....

"The Edelbrock Performer RPM continues to impress me as a 6,000-rpm and under choice. As a dual-plane or 180 degree design, the manifold produces more useable torque in the midrange with some of the larger-port heads than do most of the 360 degree designs. At 5,700 rpm on a 455, and 6,200 rpm on a 400, the party is just about over; but below these levels, it seems to increase the average torque output handsomely."

Different combinations will be different. Example, Ken Crocie did a very nice 455 based build featured in Pontiac Enthusiast magazine using Edelbrock cylinder heads with no significant port work, cleaned up only. He used a large hydraulic flat tappet cam. He tested both the Performer RPM intake and a Torker II intake using a 850 Holley carb. The Performer RPM showed great horsepower across the board when compared to the Torker II intake. The best run with the Torker II with a 2-inch spacer was 570 hp at 5900 rpm with 573 lbs-ft at 4300 rpm. The Performer RPM yielded a best of 572 hp at 5900 rpm with 582 lbs-ft at 4400 rpm.

Personally I've had a Performer RPM intake come within 20 hp to a Victor intake with mild ported Edelbrock heads, 580 hp vs 600 hp. And at a slightly lower peak power rpm as expected, 5800 rpm vs 6000 rpm. At peak torque rpm they were about the same with 589 ft.lbs torque, but the RPM intake as expected had better torque numbers at a lower rpm at the start of the dyno pull.



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[scott70]

Originally Posted by RocktimusPryme

Like was said earlier, I don’t think it costs as much extra as you think for the heads. I considered the ported iron route, but then realized I was t rally saving any money. I ended up buying a set of used iron heads and had them gone through/ported.

The roller on the other hand is way more expensive.

Cost really wasn't the main thing I was getting at. I'm talking about someone that gets out of the box 300 CFM eheads, mildish roller cam and a decent intake and make 500 /550. And then performs at that level on the track. I would think with that combo the power level would be alot higher than lesser cfm iron. Maybe they're not spending any tuning time on the alum, roller setup. Years ago I took out the original drivetrain out of my GTO for a year and threw in a iron headed,(250cfm) 455, hft ultradyne ra 4 similar cam, t2 intake, street gears,ps,pb, through the exhaust to 11.7 at 115 mph at 4000 lb. Seen plenty of alum, roller combos that couldn't do it. And my original motor with #64 heads,iron intake.ra 4 size cam and qjet made 491/570 trq.

[Steve C.]

A change from factory cylinder heads to aluminium aftermarket heads....

https://www.hotrod.com/articles/hppp...ylinder-heads/


https://www.hotrod.com/articles/ccrp...-for-pontiacs/


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[pastry_chef]

Good find Steve, this one was using that infamous XR276 cam, compression ratio was 10:1 with the aluminum and made 503 HP.
https://www.hotrod.com/articles/hppp...ylinder-heads/

Cast Iron 6X test comments -

These factory heads when treated to RaceKrafters’ porting expertise and state-of-the-art equipment produced stunning results. The Mule consistently returned dyno numbers of between 492 and 494 hp and was very insensitive to octane. We were able to make that power on regular grade gasoline, though at times we did try higher-octane fuels with little to no gain.
In addition, the combustion event when qualified for efficiency by the amount of ignition lead required was also quite impressive. With a 9.1:1 compression ratio, the Poncho with the 6X cylinder heads only required a maximum spark timing of 32 degrees.

Looks to be the same engine as this article?
https://www.hotrod.com/articles/hppp...e-stuska-dyno/

[scott70]

Hi

Originally Posted by Steve C.

A change from factory cylinder heads to aluminium aftermarket heads....

https://www.hotrod.com/articles/hppp...ylinder-heads/


https://www.hotrod.com/articles/ccrp...-for-pontiacs/


.

The first article is somewhat what I'm talking about. No roller cam but the gains weren't very much over a ported iron head and a roller probably wouldn't have done much additionally. Like I said,,I've seen/ read out of the box 0 port ehead(300 CFM),roller cammed street car running 12's with Dyno #'s to match.. With the additional airflow and better cam they should be doing better than that in my opinion. I know a milder cam is not taking advantage of the biggerr cylinder flow.Remember I'm talking healthy streetcar not all out race engine. Or take those old iron cylinder head that you've had laying around for years and have them ported and have a heck of a nice Street engine. And a well-chosen flat tappet cam you can save yourself some money and have Street performance as an equal. If 550 horse and up is your goal then thats a different story. I guess what I'm saying is that a good flowing aluminum heads, roller cam doesn't automatically mean significantly higher HP and a fast car.

[P@blo]

Originally Posted by Steve C.

Many in the Pontiac community do not have the small runner volume syndrome



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Touché, Steve? Like I mentioned it can be done with factory stuff or aftermarket. Heck you don't think you are reading unbiased product reviews in that type of material do you? It's basically a paid advertisement.

[Steve C.]

“You can’t make a Pontiac head big enough. You can make it wrong, but not too big.”

Ken Crocie



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[johnta1]

I know a milder cam is not taking advantage of the biggerr cylinder flow.

Basically answered your own question?

A 300 cfm head is probably rated at this for .700" lift?
When you put a .550" lift cam in, you are wasting a ton of power.

Also would imagine that a higher flowing head would make peak HP at a lot higher RPM range than 5000 RPM?

So, if the combo isn't matched to what the engine needs, it will be slow.

[Steve C.]

"Heck you don't think you are reading unbiased product reviews in that type of material do you? It's basically a paid advertisement."

I believe Rocky Rotella who wrote that article is competent.

Most Popular Books written by Rocky:

How to Rebuild Pontiac V-8s
The Definitive Firebird & Trans Am Guide 1967-1969
The Definitive Firebird & Trans Am Guide: 1970 1/2 - 1981
How to Rebuild Pontiac V-8s
How to Build Max-Performance Pontiac V-8s

“Researching Pontiacs is a sincere passion of mine and there hasn’t been a day in my life where I haven’t woke up striving to learn more about Pontiacs than the day before.”
— ROCKY ROTELLA

There is a good reason Jim Hand asked him to write his second book !


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