Pontiac 455 cam recommendation

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pmd400
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Pontiac 455 cam recommendation

Post by pmd400 » Thu Oct 13, 2016 7:21 am

Hi
Iv read plenty of articles, books and forum threads on cams. Iv studied a couple of vizards books, Jim hands Pontiac book as well as several articles and forum threads. Old school Pontiac says to go wide lsa and dual pattern cam. Vizard books tell me tight lsa and single pattern cam. Iv read recently on this forum that lower exhaust lift and less aggressive exhaust lobe is beneficial. So anyway, I'll get to the engine specs
Pontiac 461 - bore 4.18, stroke 4.21
Rods length 6.625
9.4:1 compression
Edelbrock p65 dual quad/dual plane intake
2 edelbrock 600 carbs
1 5/8 diameter/unequal length primary headers
2.5 x pipe exhaust. Mufflers to be used but not yet purchased
6x heads. Flow as follows
Lift Intake Exhaust E/I ratio
.100 76 54 72%
.200 134 117 88%
.300 181 154 85%
.400 219 178 81%
.500 229 194 85%
.600 229 202 88%

Car is a '72 firebird, 3500lbs
Rear is 2.41 or 2.73(have both)
Trans is a Richmond 5 speed, ratios are
1st - 3.28
2nd - 2.13
3rd - 1.57
4th - 1.24
5th - 1.00

Car is a street car. Power brakes are a must. Engine will never go above 5500rpm.
Any recommendations will be much appreciated.
Thanks

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Re: Pontiac 455 cam recommendation

Post by Walter R. Malik » Thu Oct 13, 2016 9:00 am

Use something smallish at .050" and fairly fast off the seat with those size rear gears.

Personally, I would use a "retro fit" hydraulic roller camshaft.
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Re: Pontiac 455 cam recommendation

Post by Walter R. Malik » Thu Oct 13, 2016 9:02 am

Use something smallish at .050" and fairly fast off the seat giving just over .500" valve lift with those size rear gears.

Personally, I would use a "retro fit" hydraulic roller camshaft.
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Re: Pontiac 455 cam recommendation

Post by Keith Morganstein » Thu Oct 13, 2016 9:07 am

One thing to beware of when selecting a cam is the Pontiac installed height is low, they use short springs. It gets challenging to fit a decent spring, even around .500" lift with stock heads and valve length.

You can take quite a bit off the spring pads, at least .060" which helps.
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Re: Pontiac 455 cam recommendation

Post by Fireonthemountain » Thu Oct 13, 2016 9:24 am

I would recommend this cam, to most wanting tire burning power, cheap costs, and great vacuum around 18 inches. Its a generic grind found and sold under many brands, with many prices from about $40 up. Smooth idle and good gas mileage. As a roller grind it would be hard to beat, for what you seem to want, but a lot more costly. Any lope you will lose vacuum. It is running some 11s in a similar Olds, but his heads were home ported for better flow that what you have. He is running a 3.42 and a 700R4.

http://www.hotrod.com/articles/camshaft ... n-testing/

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Re: Pontiac 455 cam recommendation

Post by RevTheory » Thu Oct 13, 2016 10:17 am

What is the Pontiac lifter diameter? That could open a few doors if you did some research.

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Re: Pontiac 455 cam recommendation

Post by steve316 » Thu Oct 13, 2016 10:30 am

Sense the .842 lifter size there would be even greater gains from the hydraulic roller cam.

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Re: Pontiac 455 cam recommendation

Post by cstraub » Thu Oct 13, 2016 10:44 am

Your I/E ratio is what I have seen when camming Pontiacs. I've been putting reverse splits in them, more duration on intake than exhaust. Nothing but happy customers in GTO's and Firebirds.
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Re: Pontiac 455 cam recommendation

Post by tjs44 » Thu Oct 13, 2016 10:55 am

With the low first gear of your trans and the CI of that motor I would look at the Comp hyd roller lobes 3122 3120 236-244@50 on a 112.Im sure there are similar lobes by others.I have this cam in a 4in stroke engine with a 2.67ish TKO.Plenty of vac to run power brakes.Tom

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Re: Pontiac 455 cam recommendation

Post by mag2555 » Thu Oct 13, 2016 12:10 pm

455s are easy to over scavenge in the Exh side, and yours would be so with a duel pattern Cam with the Exh to intake ratio your heads have.
455s gobble up intake air real fast with how the piston gets yanked from TDC!

If your Exh ports have been gasket matched then at some point you should step up to 1 3/4" headers as many people / porters gasket match the floor of the port and that is the 100% wrong thing to do, as that is a dead flow area and matching it only makes for reversion and lesser idle quality!

The stock 1.560" installed height of the springs means that running anything more than some .465" lift is asking for trouble with out different springs for more coil bind distance and different retainers for more retainer to seal clearance!

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Re: Pontiac 455 cam recommendation

Post by My427stang » Thu Oct 13, 2016 12:12 pm

With a 1:1 tranny, I'd go with the 2.73 rear, I play with ODs a lot, and typically under 2.50:1 final gets limiting for a performance engine. You either need to drive very fast :) or you don't use 5th much. FWIW, my Ford engine, with 20+ more cubes, I ran at 2.36:1 for a while, and it's happier everywhere now at 2.63:1 final (with a 27 inch tall tire)

So assuming 2.73 X 3.28 = 8.954 SLR, that's a little tall, but not horrible. If you compared that to a car with a Muncie, it'd be about equal to an M21 with a 4.10 or an M20 equipped car with 3.55s. So the rear end looks tall, but it's not that bad and will certainly cruise nice with the right cam and tire choice.

For an off the shelf choice, I sorta like this one

https://www.summitracing.com/parts/lun- ... ke/pontiac

I haven't used it, it's a hyd roller, which I would seriously consider even though it isn't cheap. Not sure it's a UDHarold lobe, but it seems like a decent street lobe. The reason for HR (beyond ease in break in) is the longer ramp allows you a bit more advertised duration without having a cam with a .050 that is too radical to cruise in 5th. To be honest, I'd likely advance this cam to 102-103 ICL as well. It'd make plenty of vacuum and still pull pretty hard. The other option could be as easy as a 280H or XE274H flat tappet from Comp, which would work well too from somewhere around 104 ICL to 106. FWIW, I like early cam timing with a tall gear, seems to make them a bit easier to tune without hurting the top end, assuming you don't try to make the cam something it isn't

That of course is adapting an off the shelf cam, you could chase the perfect cam, and you'll likely get a wide range of recommendations, but it sounds like this would be a real nice street cruiser that pulls pretty hard when asked to
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Re: Pontiac 455 cam recommendation

Post by cstraub » Thu Oct 13, 2016 12:16 pm

pmd400 wrote:Hi

6x heads. Flow as follows
Lift Intake Exhaust E/I ratio
.100 76 54 72%
.200 134 117 88%
.300 181 154 85%
.400 219 178 81%
.500 229 194 85%
.600 229 202 88%
At 75% I/E ration the duration numbers at .050" would be the same. In this build you would reference .400 and .500" IE ratio. Based on 81 to .85% the intake duration needs to be around 6 degrees more than the exhaust. Reverse split. This won't be a shelf cam.
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Re: Pontiac 455 cam recommendation

Post by rfoll » Thu Oct 13, 2016 1:08 pm

I have a 2.73 gear with a 27" tall tire. 70 MPH is around 2500 rpm with a stock turbo 350 converter. With a manual trans, you will need to pay attention to compression ratio. Bathtub chambers are not known for efficiency.
So much to do, so little time...

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Re: Pontiac 455 cam recommendation

Post by GARY C » Thu Oct 13, 2016 1:10 pm

My personal experience with Pontiac 400's is that the wide lsa cams are slow revving and lazy so in my current 79 400 4spd T/A I reluctantly tried a tighter cam based on Vizards recommendation and I'm glad I did, this cam was speced with the intent of a small nitrous shot. I ran the Comp PB 268AH-8 It's a hyd flat 268/222 276/226 on a 108 LSA with a .3100 lobe lift I run 1.65 rockers. I will probably go to a 1.5 on exhaust If I was going to change any thing it would run the intake lobe for exhaust because as well as it runs I will probably never run nitrous on it. If I remember right his NA cam was 1 degree less than the intake on the exhaust side on a 106 LSA.

My engine is 9.1 with a mildly ported 6x head and pulls 14" vacuum at an 850 idle with 18* initial timing I think the vac would come up a cpl of #'s by reducing the exhaust but I have no problem with power breaks now. The low end tq is strong enough I will probably drop the gear from a 3.42 to a 3.08 for a better cruise rpm.

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Re: Pontiac 455 cam recommendation

Post by pmd400 » Thu Oct 13, 2016 2:40 pm

Thanks for the replies. I probably should have mentioned that I'm after a hyd flat cam. Lifter diameter in 0.842. Valves are about .120 longer then stock. Also Iv already got 1.65 rockers

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