Pontiac 455 cam recommendation

[Walter R. Malik]

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

EXACTLY ... wyrmrider
I don't read anything in this first post about a hydraulic FLAT TAPPET camshaft but, I do read "Any recommendations will be much appreciated".

Not until much later is it even mentioned.

[CamKing]

Everybody's attention and priority seems to be with Wide Open Throttle so, I guess that is the only important thing and all that matters here ... have at it.

The cam I recommended will be extremely responsive at part throttle, and light the tires at will.

[wyrmrider]

Mike
are the head flows for his Pontiac unusual?
I see you are going with similar intake and exhaust
and
If he's not just driving around town stop and go he can use the extra duration
freeway on ramps, passing on the highway
I still think 230 is too big
OP heavy or light flywheel? I'm not recommending a light flywheel with your combo

[My427stang]

FWIW, certainly not a direct comparison because the engine design is so different.

However, in my 445 FE 4 speed 4100 lb 4x4 truck with 3.50 gears and 32 inch tall tires, I run a Bullet lobe at .580 lift, 236 @ .050, 282 adv, both intake and exhaist, 106 ICL 112 LSA. It's a solid cam, recommended lash at .027, I run it at .016 too, with a 750 Holley and heavily ported but fast iron heads flowing over 277 cfm and a worked RPM intake and it'll pull down nicely. I don't tow, but the long arm likes duration.

I like Mike's cam because it opens the valves more than a 280H from Comp, but I can tell you, a 280H is sure not a radical piece in a 460 inch motor, and I am sure Mike's isn't either.

[Geoff2]

88% E/I flow percentage for Pontiac factory heads that have been ported are not uncommon. I would say 75-80% is the most common range, & I have seen as high as 94%.

Pontiac guru Pete McCarthy, Pontiac racer, author of two Pontiac books, founder of Pontiac Enthusiast magazine & one time editor of HPP magazine said it best in one of his articles, 'Sciencing out the Pontiac engine': stop worrying about the exhaust [ ports ] & figure out how to get more flow through the intake ports!

[CamKing]

Mike
are the head flows for his Pontiac unusual?

You've got an intake port that flows about the same as a SBC 492 head, trying to feed 461cid, and to evacuate the cylinder you've got an exhaust port that flows about the same as a BBC Brodix BB1. If this was a race engine, I'd run 4 degrees less exhaust duration, and a tighter LSA, but that can cause heat issues on the street. By not going 4 degrees smaller on the exhaust, and widening the LSA by 2 degrees, I've kept the overlap the same, but I'm opening the exhaust 4 degrees earlier to keep the cylinder temp in check.

[CamKing]

Hmmm, well then just like a 2 barrel carb restriction class.

Not really. With a restricted carb, the high velocity/restriction point is at the carb, and the velocity/density in the port is too low.
With a restrictive port, the velocity and density in the port is too high.

[wyrmrider]

Mike wrote
You've got an intake port that flows about the same as a SBC 492 head, trying to feed 461cid, and to evacuate the cylinder you've got an exhaust port that flows about the same as a BBC Brodix BB1. If this was a race engine, I'd run 4 degrees less exhaust duration, and a tighter LSA, but that can cause heat issues on the street. By not going 4 degrees smaller on the exhaust, and widening the LSA by 2 degrees, I've kept the overlap the same, but I'm opening the exhaust 4 degrees earlier to keep the cylinder temp in check.>

Thanks, makes lots of sense and solves a problem before it comes up

[Geoff2]

Further to my post on Oct 24 about Pete Mc Carthy's comments, here is the full paragraph in context.

PE Magazine Vol 1 Number 2 Autumn 1993.

" Exhaust airflow at BDC was increased by some 10% [ E/I 73% ]. Exh airflow from .100 to.400 lift. If exh deficiency were a serious problem, one would expect at least some kind of improvement with the increase in exhaust capability on this engine. In back-to-back tests [ two pulls to ensure accuracy ], there was virtually no change in either torque or hp! As I have tried to convince Pontiac enthusiasts for some time, stop worrying about the exh ports & figure out a way to get more air through the intake ports, especially on high compression racing motors!"

In another article by Pete, June 1992, when he was at HPP magazine. A number of parts combinations, among them a single pattern v dual pattern cam, were tested on a street driven 455. Pete's comment: "While too many variables existed to make a definitive judgment, it is safe to say that a single pattern cams loses nothing to a DP cam.

[GARY C]

Further to my post on Oct 24 about Pete Mc Carthy's comments, here is the full paragraph in context.

PE Magazine Vol 1 Number 2 Autumn 1993.

" Exhaust airflow at BDC was increased by some 10% [ E/I 73% ]. Exh airflow from .100 to.400 lift. If exh deficiency were a serious problem, one would expect at least some kind of improvement with the increase in exhaust capability on this engine. In back-to-back tests [ two pulls to ensure accuracy ], there was virtually no change in either torque or hp! As I have tried to convince Pontiac enthusiasts for some time, stop worrying about the exh ports & figure out a way to get more air through the intake ports, especially on high compression racing motors!"

In another article by Pete, June 1992, when he was at HPP magazine. A number of parts combinations, among them a single pattern v dual pattern cam, were tested on a street driven 455. Pete's comment: "While too many variables existed to make a definitive judgment, it is safe to say that a single pattern cams loses nothing to a DP cam.

It's no different then the long standing battle between men and woman...Emotion vs Logic!

[Walter R. Malik]

Theories are great for a beginning however, actual RESULTS don't lie.

[Geoff2]

And the theories are......

And the results are......

[tjs44]

WOW,6 pages devoted to a pontiac street 455!Tom

[pmd400]

Cam I ended up going with was
Intake
270@.006
224@.050
.318 lobe lift

Exhaust
272@.006
222@.050
.295 lobe lift

108lsa, 105icl

Engine pings badly. Still pings with vac advance disconnected and full advance only at 30* all in by 3000rpm. Cranking compression test were 180-190psi for all cylinders.
Thoughts?

[John Wallace]

Why not go with Camking's recommendation?

With that 4.21" stroke, you need some duration.
This cam will peak @ 5,100rpm, have plenty of vacuum, and a smooth idle. I would not go any smaller
Cam# P455, H71330-110
228/228 @.050"
.330"/.330" Lobe Lift
.544"/.54" Valve lift w/1.65 rockers
110 LSA
107 ICL