# Opinions on Cam Selection



## john67455 (Aug 15, 2015)

I bought a bunch of stuff for my Pontiac 455 from Bruce Fulper (Rock and Roll Engineering) in the mid ‘90’s. Unlike a lot of other opinions, I had pretty good luck dealing with Bruce. He sold me a set of the 72cc Edelbrock heads (serial number RRE-2-36), when they were still very new to the market and a cam (among other things). The heads were supposed to have been ported and they seem to work well. The odd thing about my set up is the cam has slightly more intake duration than exhaust (248/244 @0.050”), 110 Intake centerline and 110 lobe separation angle and .563”/.575” Int/Exh lift with 1.5:1 rockers. The cam is a Comp Cams, Hydraulic Roller, with grind # P3318/3120/HR10. I haven’t seen other cams set up this way (before or since), and I’m interested to know your opinion on this. I understand that the exhaust ports on these heads tend to flow quite a bit better than the traditional Pontiac head, potentially allowing for less exhaust duration. But, since I haven’t seen this type of cam elsewhere, I’m wondering if I am losing power because of my choice in cam. Everything is still going strong and I haven’t had any problems with the engine. Don’t drive it all that much, but it still works well. But as things go, I’m looking to get even more power out of this engine. With the static compression ratio around 12.4:1 and the dynamic around 8.9:1, I do run race gas or 100 low lead. I’m not worried about this hassle and I want to make this thing as powerful as practical, without doing anything to the heads or bottom-end if possible. I have a stock hood, so I am limited on hood space, but any suggestions you have I would love to hear them.

Now after about 20 more years of experience, I’m wondering if you have any updates on cam recommendations for my combination.

A bit more background on my car and combo:

1967 Firebird Convertible (I know it's not a GTO, but I know there are plenty of knowledgeable Pontiac experts on this forum).
1972, 455 CID, bored 0.030”, 4 bolt mains
Stock, factory crank 
Edelbrock 72 cc heads prepared by RRE.
Torker 2 Intake
850 Holley, mechanical secondaries.
1 3/4" Headman round port headers, 2.5” exhaust (looking to upgrade to 3”).
Borg-Warner Super T-10 4-speed (installing 12” aluminum flywheel and clutch from Mcleod soon).
3.73:1 rear end.

I really appreciate your help on this one, and if you have time, I have a couple of other questions about potential upgrades and performance improvements:

1. Should I upgrade to larger headers (like 1.875”)?
2. Is a 2 ½” exhaust, with a Flowmaster cross-flow muffler (dual in and dual out) suitable for this engine.
3. Do Edelbrock heads really like 40 degrees spark advance?
4. Is the 850 carb suitable (I haven’t checked manifold pressure at WOT yet), or could this cause an air flow restriction at high RPM?
5. Have you guys ever rigged up a knock sensor on a set up like this (not a computer controlled car)? I think a knock sensor would be a great tuning aid, but I haven’t seen much available out there.

Thanks for your help and I look forward to your response.


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## Pinion head (Jan 3, 2015)

The typical use for a split duration cam with more duration on the intake side is in a turbo build. Have no idea what Flopper was up to with that particular cam... with the 72 E heads, and the flattops, there has got to be a far better cam selection. It would help to be exposed to the experience from many builder/owners that have built and ran the 72cc E headed 462-474 Pontiac over the last 2 decades. With that in mind, you're going to get a much larger response if you post this question on the Ames/ PY forum in the street or race section.


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## oldskool (Apr 26, 2015)

*Py*

"...you're going to get a much larger response if you post this question on the Ames/ PY forum in the street or race section"


Yeah, then just sit back and watch the debate/argument begin. Them guys get nasty with cam debates. All the engine builders have a different idea, and can site several dyno and drag strip results to prove that their opinion is correct.

But hey, it's good entertainment. Post and enjoy !


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## Pinion head (Jan 3, 2015)

I seriously doubt there is going to be nasty cam debates, maybe some "what the H was Flopper up to with his cam advice? " 

72cc E head on a 462-474 has been done many times, usually in older street/strip or budget strip builds. My suggestion was to ask in a venue where MANY can relate their personal experience with that sized engine and those particular heads.


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## PontiacJim (Dec 29, 2012)

Like anything else, you will get many opinions. I take it you are going all out race on this engine, so build it as such. You have to decide where you want to put your power band, and that will heavily dictate the cam choice.

Have you tied the subframe and added a roll cage to stiffen the body/chassis?

Don't know why the cam spec you have, but the fact that the exhaust supposedly flows better on your heads would have changed the intake-to-flow ratio and I would think that Fulper was adjusting for that in your cam spec. The cam seems to me to be a street-strip cam. Not a big fan of 110 LSA cams(non-roller) as they pull like a freight train up to a point and then drop off fast, and this may be what you are experiencing. These work best in low compression engines -in my opinion. You could play around with the cam advance/retard to see if this changes anything. 

My opinion is that you will need 2" headers to move the exhaust gases and I'd go with 3" exhaust pipes, dual low back pressure mufflers. I can't see how a single crossflow muffler could be any good. That could in itself be a restriction and choking off power. Have you ever tried uncorking it and going open pipes just to see?

Not a fan of aluminum flywheels as you will lose rotating mass/inertia on take-off. Your car may stumble, bog, or backfire through the carb which is a probability with 3.73's, and you may find yourself slipping the clutch a lot to compensate for this to keep your RPM's up higher on the launch and that will kill ET's and wear the disc quickly. No expert here, and I assume you contacted Mcleod on your choice, but this is my understanding from my reading.

From what I have read, the E-heads can like up to 40 degrees total advance, but seems a lot. 

The 850 may be too small, but it may be more streetable and set up for your combo. If you change the cam and you plan on higher RPM's, then you may want bigger. Assume no flow problems through the gas lines.

Your best bet would be to get with one of the big name Pontiac builders and run your specs by them, tell them your goals, and get the parts they suggest to get the results you are looking for. These guys know their Pontiacs and you would be better with their recommendations.:thumbsup:


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## oldskool (Apr 26, 2015)

*PY Cam Thread*

Cams for 455 engine builds. - PY Online Forums


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## BearGFR (Aug 25, 2008)

Maybe when your engine was built, that cam was the 'best available'? I'm most familiar with Comp Cams myself, but they aren't the only game in town. How does the XE294H look to you? (250/256 @ 0.015 on 110, .516/.524 with 1.5:1 rockers).

With 3.73's and a 4 speed you don't have to worry much about bottom end (as if that's ever really a problem in a Pontiac  ).

As far as lead, my 461 with 72cc E-heads (ported by Dave Wilcox at CMVS) seems to be happiest with 35-36 degrees. That's on 93 octane at 10.1:1. I suppose it's not out of the question that your engine on slower burning race gas might like more. Only way to find out for sure is through track testing under tightly controlled conditions.

Generally I caution people about going bigger on header primary size and exhaust. Too big is worse than too small, but in your case with that many inches and as serious as it sounds like your engine might be, it just might be a good idea. Just be careful.

As an aside, be very careful about lifters. I read an article just today about Lunati rollers for Pontiac. Apparently, the oil band is too low and allows the edge of the band to peek out of the lifter bore by a few thousandths at the bottom of the lifter stroke. Just enough to let it catch on the edge of the bore, which eats it up rapidly - leading to "nothing good".

I'll second the recommendation on talking to experienced builders, one in particular I really like is Jim Lehart at Central Virginia Machine Service. When I was planning my build, he was the only one of the 'name' builders who was willing to give me the time of day and actually discuss things with me. All the others, Butler included, either wouldn't talk to me at all or just wanted to give me some cut and dried formula without being willing to explain the logic behind their recommendations.

Whatever you decide, good luck and please do let us know how things go.

Bear


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## john67455 (Aug 15, 2015)

Thank you all for the feedback so far. I'll be sure to keep these points in mind while tuning my car in the near future. I'm fortunate that my old man felt the need to install a Mustang chassis dyno in his garage recently. So, I'll be able to do some very detailed and controlled testing. I'll keep you updated on the results. Any additional advice would still be appreciated.

I have one more question, possibly best for another thread, but here goes:

What is the tallest manifold/carb that can fit under a stock 1967 Firebird 400 hood?


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