[rexs73gto]

I had the RA IV Crane Blue print cam in my 462 ( 30 over 455) & I have used it several engine builds including the one in my car right now which is a 413 (60 over 400) & it runs great. I have round port E-heads & 3:73's in the rear & RA IV manifolds & a Q-jet. It runs great & has plenty of vacuum fro the P/B's. So you can use it with the 5 speed & a bigger gear & be just fine.

[Steve C.]

"Shouldn't the exhaust system come in to play here? Say you have an 80% exhaust to intake ratio on the head flow but instead of headers you run ram air exhaust manifolds..... Does this negate some of the exhaust to intake ratio of the heads?"

Good point. I would suspect you are correct regarding the total exhaust system in play. But honestly I do not know about your second question. Hopefully someone here can comment.

Here is a clue from the internet:

DUAL-PATTERN CAMS: A dual-pattern cam is one that has different duration and/or lift specs for the intake and exhaust. Usually, the exhaust lobes have more duration and lift than the intakes. Depending on the engine, this can be beneficial for engines with poor exhaust-port flow or otherwise-restricted exhaust systems.


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[Steve C.]

Dual pattern Cam vs. Single pattern Cam.

Included in the discussion are tech comments from Isky cams. They are a proponent of single pattern cams in many situations.
Also David Vizard, he is a proponent of single pattern cams (particularly for street type applications). But I will note many feel David's work is based on Chevy applications and their exhaust ports might play into this.

http://www.hotrodders.com/forum/dual...cam-81564.html



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[Steve C.]

And here the subject of the entire exhaust system is mentioned, however the subject is based on Chevy talk....

You can also pick a cam based on airflow, but not on total flow numbers. Along with compression and operating range (engine speed at cruise, often dictated by gearing and tire diameter), the difference in airflow from intake to exhaust ports offers a guide for duration figures. For example, if your exhaust ports flow 60 percent of your intakes’ cfm figures (which is pretty restrictive), then use a lot more duration on the exhaust ports, regardless of lift. This applies to many street-driven cars and suggests choosing a split-duration cam, of which there are many to choose. Similarly, most dyno tests done both by manufacturers and sanctioned by magazines use dyno headers, which give much better exhaust flow than the corresponding car’s exhaust system. A dual-pattern cam with more exhaust than intake duration can make up for some of this backpressure.
Duration is also a concern when dealing with car weight. A 350ci engine in a light car with minimal exhaust restriction can get away with less difference in duration from intake to exhaust timing, whereas a heavier car will enjoy more of a difference in duration. Here’s an example: If we have a 2,800-pound ’68 Nova with a 350 and a fairly standard driveline and exhaust, it could use 222 degrees duration on both the intake and exhaust for good all-around street performance. However, in a 4,100-pound ’67 Impala with an engine of the same size and general state of tune and the same engine operating speeds, a split-duration cam with 222 degrees intake duration and 236 degrees exhaust duration would perform better (perhaps much better) than the single-pattern cam used in the Nova. In general, the lighter the car, the more free-flowing the exhaust; therefore, the less duration difference it can get away with. Not total duration, mind you, just duration difference from intake to exhaust. With some cams for late-model cars, 10 to 15 degrees of duration difference is commonplace.
Keep in mind that lobe separation angle has a direct effect on cylinder sealing (the portion of time both valves are open versus closed). Narrower angles seal the cylinder longer than wider angles do, increasing low-end torque. If intake and exhaust valves stay open too long at intake and exhaust stroke transitions, the exhaust can blow out the intake valve, and the intake charge can be shoved out the exhaust port. This makes idle quality very poor; therefore, we usually see “street” cams with no less than 110 degrees of lobe separation.


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[pastry_chef]

A nice thing about solid cams is the ability to vary lash to test what an engine really wants.

http://www.chevelles.com/forums/showthread.php?t=389587

Here Straub recognized deficient exhaust flow of the head. I/E ratio below 70%
The cam only had 6 deg more @ .050 for the exhaust.
Chris recommended tweaking the lash to band-aid the cam.
On the next track run the car gained 2 tenths and 3 MPH with only lash.

[ponyakr]

This thread, once again, shows that when it comes to cam choice, it all depends on who you ask.

[pastry_chef]

Originally Posted by ponyakr

This thread, once again, shows that when it comes to cam choice, it all depends on who you ask.

Very true.
It would be interesting to see some Pontiac V8's run custom cams like Straub's
I'd expect them to be different than traditional values and impress.
Narrow LSA does not always need to idle like crap.

[Steve C.]

My previous 462 ran a solid roller that was single pattern and with a 108 lobe separation. I made calls to both Chris Mays at Comp and Bullet Racing and they had no issue with my choice after I went over my complete combination including cylinder head flow numbers and entire exhaust system. The Edelbrock cylinder heads had a very high exhaust-to-intake flow ratio. I know Chris Mays has worked with Jim Butler and Ken Keeffer (Pontiac Dude) with cam development and he knows 'Pontiac' if anyone thinks it makes a difference. And I can assure you similar with Bullet Racing (we have bought 4 custom cams from them). The idle was routy as expected, I like that !, and the car had manual brakes so no vaccum issues. Also piss poor low static compression was a factor in the choice. But like the overwhelming majority of people I was not in the position to make any cam changes for comparison on a engine dyno and/or track. That is expensive and time consuming. Thus I will never know if the choice was 'the best' one.


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[pmd400]

So I ended up buying a straub cam. Hopefully engine will be in car soon.
Specs are as follows
Intake- 224@.050, 136@.200, .318 lobe lift
Exhaust- 222@.200, 130@.200, .295 lobe lift
108 lsa
105 icl

[Will]

Interesting. That seems like a small cam for a 455. Very curious to see how it works for you.

[Cliff R]

Agreed, and it woln't even come close to taking advantage of the head flow available.

As far as the dual pattern vs single pattern vs reverse pattern, over here in the Street section it's not much of a player, as more times than not the car will have a full length exhaust system and head pipes not large enough, as is the case here.

These 455 will absolutely LOVE 3" head pipes vs 2.5". We've seen 2-3 tenths/2-3mph improvement at the track with vehicles we've been involved with here that had stout 455's in them and the owner upgraded from 2.5" head pipes, to 3" pipes with an "H" or "X" before the mufflers.

In contrast, we've tried just about everything behind the mufflers from 2.5" full length pipes to 3" "turn-downs" and it makes little if any difference in ET or MPH, so basically once you get that far back the hot gasses have condensed enough it really doesn't matter much how big or how long the tail pipes are......FWIW.....Cliff

[tom s]

I run more cam than that in my 366 street engine.Tom

[ta man]

I thought we would see lift in the 540 range not 480/450..

[pastry_chef]

Originally Posted by pmd400

So I ended up buying a straub cam. Hopefully engine will be in car soon.
Specs are as follows
Intake- 224@.050, 136@.200, .318 lobe lift
Exhaust- 222@.200, 130@.200, .295 lobe lift
108 lsa
105 icl

Straub gets results!
Would be great to see a few of his roller cams in Pontiac's

[Formulabruce]

All this and I'm not sure why it needs 2 carbs... seems over kill when you can get a Q-jet to run like fuel injection. I am betting the piston tops WILL carbon up fast on this build.

[pmd400]

The reason I decided to go this cam is because rpm will be 5000-5500.
I figured their wasn't any reason to put a cam in that made peak hp at 5500rpm when it just won't be up there. Also I keep coming back to his article
http://www.dapa.org/building-a-stron...afts/#more-144
The 068 cam with 1.65 rockers was .1 sec and 1 mph in the 1/4 faster than the 041 with 1.5 rockers and regular lifters. Also states car was impossible to drive on the street.
With rhoads lifters and 1.65 rockers car was .15 sec and 1.5mph faster than the 068.
Now the 068 is a tiny cam, 212/225 at .050, .about .450 lift with 1.65 rockers

[Cliff R]

That cam woln't make power anywhere near that high the rpm range. That little cam on a 108LSA will be done before 5000rpms, if not 4500rpm's....IMHO.....Cliff

[pastry_chef]

I come up with a 5000 RPM HP peak.
Head and cam capable of 450 horsepower with the OPs compression.

[pmd400]

Originally Posted by Cliff R

That cam woln't make power anywhere near that high the rpm range. That little cam on a 108LSA will be done before 5000rpms, if not 4500rpm's....IMHO.....Cliff

I've also got a crower 60919 cam that I had intended to use. May even do a head to head test in the future. Could compare throttle response, idle quality, fuel mileage and perhaps 1/4 mile(although Iv never been to the track).

[pmd400]

Originally Posted by pastry_chef

I come up with a 5000 RPM HP peak.
Head and cam capable of 450 horsepower with the OPs compression.

How did you come up with is result? I figured if a summit 2802 cam could make power to 5000rpm than the straub cam should be able to as well.