[65nss4spdGTO]

Originally Posted by cfmcnc

Yes...you should port your heads! These things (Pontiacs) always need more air moving through them . Your head otb is about 290 ish??? in intake cfm . Can gain about 40 cfm in the induction tract. Depending on the manifold , carb and camshaft...that COULD be about 80-100 h.p.! It is very dependent on the total package though...I'd think single plane automatically but...the Performer RPM is pretty good even still. Good luck with your project ! Some pics of our CNC'd Eddy RPM here . Cheers , Johnny

X2 on porting your heads, nice work.

My 340CFM CNC program for E-heads is based on the 72cc version, I see about 20 CFM reduction when running a 87cc version based on the valve placement in the head. Have you seen a reduction running the large chamber head?

Thanks.

Calvin Hill
Hill Performance
708-250-7420

[cfmcnc]

Yes Calvin , I have... at least I can recall a set sold (87cc from Edelbrock) that seemed low (about 12 or so cfm) when we were first fooling with them...only difference...the development was done with 72cc version !
Discharge control after the valve seat is hard with that wide , flat floor chamber . Seems if we could get a rubbed chamber in these right from Edelbrock without welding them...there's more in the basic design controlling the chamber shape! It is..after all...a 14 degree head . Cheers , Johnny