Need help with cam choice

I don't think you could go too far wrong using the famous 068 cam (288/302 dur max torque @ 3000 rpm max hp @ 4600 rpm ) in any Pontiac engine. This was the original tri-power cam from 1965 and was used in various Ram air/455 applications after that.

You might look here:

Another good article that might help:

I would argue to the contrary, particularly if the heads are marginal. A cam with too much duration (and typically a consequently tighter LDA) tends to bleed off cylinder pressure at low rpm. Combine this with a low static compression ratio (like 8.4) and the motor will have major trouble getting the fuel vaporized at lower revs. The classic "solution" is to richen up the idle/off idle to load the motor with fuel in the hopes of getting enough vaporized to keep the engine running. This, however, will wash down the cylinder walls, and before long, it's rebuild time. Personally, I'd either kick that compression ratio up a full point, or I'd forget 300hp and stick with a very conservative cam profile. If the builder opts to stab in a wild cam nevertheless, I would strongly advise to install it significantly advanced to help salvage a little low end pressure.

Mark

You can't go wrong with the 068 RA/HO or RA-IV cams. They may be old but they're tried and true. I yanked a CompCams Extreme cam out of my 455 HO that the previous owner installed for a factory 068 cam. The car ran so much better and had so much more power. The factory cams have a very nice lope to them especially the RA-IV cam. None of the radical cams are going to work well with

I don't recall as it was almost four years ago now but it was something made for an engine with atleast 10:1 compression. When I pulled the intake there was a light amount of black soot from the overlap. The idle screw on the carb was turned in all the way just to keep it running and it would stall sometimes when engading Reverse or Drive(was an auto trans at the time.) Just a horrible choice for a cam in an otherwise stock engine!

Runs like a dream with the 068 now, has a nice lope, and gets 16-17MPG to boot!

I was actually thinking of a summit 2801. It's comparable to the 068 (durration) but has a bit more lift.

There's still a chance that I may deck my heads which would get me over 9:1 CR; from 90cc to 80...or so.

If I do deck my heads, what will I have to do as far as intake manifolds so that it will line up?

snipped-for-privacy@m.b.g> >

I am coming from a deep and long time involvement with mouse motors, so perhaps it isn't such an issue with Pontiac heads, but I tend to avoid milling a head for the purposes of increasing compression. To get a full point by milling, one removes enough material to effectively alter the burn characteristics of the chamber, not to mention the possibility that so much material will be removed that we've gone close enough to water that the head will overheat (maybe crack). If the head's hot and we've messed with the quench characteristics, I'd be very afraid that the motor will get into detonation before you can get enough spark lead into it to make any power.

On a related note, what are the specs of this 068 cam?

Mark

This has been the case with some of Comp's Extreme Energy series cams; with the quicker ramps, they do help to open up the top end while doing an incredible job of maintaining cylinder pressure at lower r's. When installed in a relatively high static CR motor, it is almost easy to undercam a motor. The greybeards always speak of cams with reference to advertised numbers while we youger guys tend to think in terms of .050" specs. Recently (particularly with the aforementioned line of cams) one must take into account both specs to try and gauge the overall ramp profile. Still, if the original poster keeps the low SCR, I think undercamming is the last of his worries.

Mark

-- GW - Conservational Ergonomist - note incorrect email address "It's good to yell at people and tell them you're from Tennessee. That way you'll be safe." - Gary Busey

Crappy heads? I thought the 6x-4s were fairly good....granted not the smaller chamber heads from the late 60's/early 70s.

compression

The 068 has around a .408/.407 lift and a 212/225 or so duration, as I recall.

much material will be

Your point is very well taken and the "greybeard" that's building my 400 esentially said the same thing about under camming the 400. That's why he's chosen the Compcam 270 to go in my block. With a standard bore, and 6x-4 heads he says he can get 360 HP and 440 ft-lbs of torque out of it.