Has anyone infos about pontiac heads #11 of a 350 cui engine from 1970? Chamber size (i found different infos)? c.r. with a mild cam like summit 2801 and flattop pistons without notches? Head flow? Flow data for desktop dyno? Are these bad/midrange/good performance heads?
Static CR = 8.0:1 with flat tops, dynamic CR will be low, probably <120 PSI.
Summit 2801 will be too much cam for this combination.
Look for big-valve, 72 CC heads and mill them to 65 cc for use in Germany with 95 Octane bensin.
Heads such as: #670, #16 - 1968, not 1970, #62, #12, #13, #31, #997 would be far better on the 350, in my humble opinioin.
However ...
You can open the seats for large valves, you can do some porting work on the heads and you can have screw-in studs installed, but the amount of performance improvement will be limited because of the relatively deep chamber and the port designed into the head. For the amount of money it will cost you to convert these heads over to "performance" heads, you are far better off buying prepared heads of the correct type.
i put in the engine like i bought it. You told me before (headers installing) that the heads are "Scheisse", but i want to try the engine before disassembling it. I don´t know which parts (pistons, cam) are installed, i only know that the engine (350cui of 1970) is 0.030 over. The problem is, that it has no low end torque, but runs very fine above 3500 rpm. It beginn to splutter above 4200 rpm (i think the valve train wasn´t matched to the cam, which is too sharp for the engine). Rear end is a 3.55. Intake is a 1968 HO with a Quadrajet of 1978 (original carburator is still there, but needs rebuilt) This weekend i will measure the cam and then decide what to do. Other heads (if i find some) or another cam. Maybe somebody has other ideas.
PS:Q and all other fgf-members: let me know, when you are in germany (near munich)
You are on the right track. Measure the cam. If you can get a degree wheel, also check the opening and closing of the intake valve. While you are at it, check the slack on the timing chain the same way that TOHCan told Yellowbird. Let us know what you find, and we'll do our best to put together a solution that works good with what you already have.
Two ideas come to mind. The sputter at 4200 might be ignition related, either "points bounce" - they are set too wide (dwell too long) or some other timing related issue like broken mechanical advance spring or springs. I can't imagine the cam causing such a narrow power band, even on that engine.
The other idea is going to sound like a broken record: Advance the cam. With the duration of the 2801 nearly the same as the 068 Ram Air cam, the intake valve is closing later than it should for your engine/head combination. That's what's taking away the low-end torque. And since you have such small valves, you are not getting the power back at higher RPM.
I know you must work with what you have. I may have been a little too harsh about my critique of the #11 heads, but that's only because there are better heads.
Q
PS: I will gladly stop by in Munich next time I am in Germany. I will also be looking for someone in Heidelberg. Maybe a trip along the Romantische Strasse in a 1969 Firebird ...
