Guest 73TPIZ Posted September 5, 2002 Share Posted September 5, 2002 Right now i'm running stock '86 305TPI with just a mild cam. Future plans are 8/1 compression 350TPI with supercharger. Will 350 heads bolt to my 305 and drop my now 9.5/1 compression down to 8/1. That way I could find heads and S/C to get all the bugs worked out while I build my 8/1 comp 350 bottom end. Just a thought and would like some input. I've heard the rumors of bolting double hump heads to 305s but just don't know. I know the bore is almost a 1/4" wider but if the water holes, etc. line up it seems the bigger chamber would drop the comp ratio substantially. Thanks for any responses to what seems to be a really stupid question the more I type. Take care. Quote Link to comment Share on other sites More sharing options...
Mike C Posted September 5, 2002 Share Posted September 5, 2002 Depends. 305 heads, 58cc chambers usually. 350 heads, it depends. Up until 1971, 64cc chambers. Then with the advent of the aluminum head L-98 those had 58cc chambers like a 305. The TBI 350 in caprices had 64cc chambers for 9.5:1 but trucks continued to get 76cc. Then in 96 with the Vortec headed motors, they went back to 64cc on the 350. Vortec 305 still has 58cc chambers. A 64cc head on your 305 should drop compression to 9:1 from 9.5. Also beware of exhaust manifold bolt patters. In the late 70's they added another manifold hole to one of the end exhaust ports. Early heads that don't have this won't bolt up to later manifolds that need it. 76cc heads on your 305 should net 8:1 Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted September 6, 2002 Share Posted September 6, 2002 I thought there was a chance of the valves hitting the edges of the 305's smaller bore using the 350 heads? Regards, Lone Quote Link to comment Share on other sites More sharing options...
Guest 73TPIZ Posted September 6, 2002 Share Posted September 6, 2002 Hey guys, thanks for the replies and the numbers you gave me Mike. Lone, I hadn't thought of the valves hitting the walls, thanks for the warning. If I can't find anyone here that knows for sure I'll check with some machine shops in the area. I would guess any decent shop has seen about everything tried on everything. Again, thanks. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted September 6, 2002 Share Posted September 6, 2002 A further cylinder head inquiry from Mr. Grumpy Vette. There were some 305 Torquer Heads for sale awhile back in the Sell thread Quote Link to comment Share on other sites More sharing options...
Guest LIghtningZ Posted September 6, 2002 Share Posted September 6, 2002 Or you can do like we do for circle track sometimes and put the 305 heads on the 350 for some serious POP!! if you work the chamber out to a 350 head gasket it bumps comp. about two points 8.o:1 = 10.0:1 !!! Quote Link to comment Share on other sites More sharing options...
Mike C Posted September 6, 2002 Share Posted September 6, 2002 I did not mention the valve thing, but should have. 2.02 intake and 1.6 exhausts won't work, and if notching the bore did make for clearance, the edge would still be too close to the cylinder wall and would be shrouded. Since original GM 2.02 cylinder heads disappeard with the L82 Corvette in 1981 they are as rare as the proverbial hens teeth, but should have been mentioned! Quote Link to comment Share on other sites More sharing options...
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