I just finished rebuilding a 350 out of a 1969 Olds but I could not afford at this time to have the heads redone. The original heads were stamped with a 6 and the heads I used which I new to be in good shape are stamped 3A. Could someone inform me which heads are better. I will eventually have the original heads redone but I am just curious what the performance difference may be. Thanks

 

The 3A heads are lighter castings, lots of meat trimmed out. I don't think they hold up as well against say overheating, based on the junked engines I have seen. If they have not been abused, they should be serviceable. Probably a chamber size difference, but not sure if it's negligible- not many folks mess with the 3A and up era heads. The valves might be expected to be smaller on the smog era 3A head, but they would still be serviceable. 3A heads probably have rotators on all valves.

Beware of the use of pushrods with 3/8 ***** on the smog era engines- you want to make sure that the pushrod ***** are the same size as the lifter cups and the rocker receptacles.

 

I did use the pushrods that went with the 3A heads just to be on the safe side but as far as I could tell they were the same, got the engine done and put in and it runs great just need to get a different carb or try to rebuild the quadrajet 4 bbl. idle circuit is not to good, from what I can tell the floats might need adjusted, off idle is smooth and strong. Thanks for sharing your knowledge.