The Stovebolt Site Forums The Shop Area Engine Shop 1970 gmc half ton with 307

OK, I picked my next restoration project. It's all original and I'd like to keep the 307 but wouldn't mind a little performance boost. I have a set of 327 heads #3782461 (64cc 1.94'" intake valve, 1.5 exhaust valve) laying around and was wondering if that would be an improvement. The original heads are 3927185 (70cc 1.72 intake and 1.5 exhaust valve. My thinking is the smaller chamber and larger valves will be a performance improvement. Also looking at dropping on a 4 barrel intake vs the 2 barrel intake with a quadrajet. Thoughts on this guys?

Those heads may not have the bolt holes in the front to mount the alternator, a/c . But they will boost the compression a little bit, a quadrajet will help a little also. Might want to go with hei dist while you have the distributor out .

A better choice would be the 53CC head for a mid-1980's 305 with slightly larger exhaust valves fitted. Use a 1.6" exhaust, regrind the seats to fit them, and do a little pocket porting.

14022601 — 1980-1986 267 or 305, 1.72/1.5 or 1.84/1.5 valves, 53cc chambers

64CC heads are scarce and expensive, and if you have a set, why not sell them to some Kool-Aid drinker who thinks they're the best thing since a pocket on a shirt? You'll make enough money to buy a set of 305 heads and set them up to get much better performance and higher compression, plus put a little profit in your pocket. Those heads will also have the accessory mounting holes for a later-model alternator and power steering, A/C, etc. if you want to install them.
Jerry