I have a stock 1979 305 2 barrel out of an impala hanging around . That ran real good . My current motor in my roc is a 1987 350 4-bolt 2 piece GM crate motor . I have to do some work that requiers me removing the heads . When I am doing all this I am going to swap cams . Will I benift from the 305 heads with the approrate cam or should I stick with the 350 heads . Have a edelbrock performer intake and allso a weiand dule plane looks the same as the eddy .

It depends on which casting the 305 heads are, and the 350 heads, as well. Post their casting numbers (found on top of the head between the springs) and we can give you a better idea of which way to go.

Hear is the 305 casting #s 378450 I found theys other #s too c 23-78 and GM T7 . I have not yet taken the 350 apart . Can you tell me if theys 305 heads are crap .

I assume you misread the number as it doesnt exist but heres a bit of specs

376450.....75-81...262/267/305..6 or 7 exhaust bolt holes, 60cc chamber


Fairly small chamber so compression will be up there.

I believe those also had the 1.72" intake valves. Some truck 350's did too, but they really are too small for any hope of performance.

I kind of though the wer poo . Thanks I will get the numbers of the 350 and see if we can come up with some cheep mods .

I'm currently using 70's 305 heads with 60cc chambers, ported, small valves on my 350 (rpm air gap, 270HR). I can't really compare them to the 58cc alum. 'vette heads which came on the motor originally. I can say they make more power vs. the ported 350 TBI heads I was running.

They do exist 378450 I looket agian .How ever the intake valves
are 1.72 and the exahust are 1.50 . Hear are my hecho en mexico head casting nubers 1998993 .

Yes, they DO exist. I just found a pair on a 1979 Mercury Mercruiser I/O engine. That's appropriate, since a marine engine should have marine heads (tie on a rope and throw them overboard). They are lightweight smogger head castings, not worthy of holding paper on a desk. I found somewhere that they are supposed to be 60cc chambers, but the one I checked was 62.4cc with a plug installed.