350 heads, different?

[GS69350]

I need this answered 100% for sure.

Do 70 350 heads have a smaller combustion chamber volume than 69 350 heads?

I was under the impression that all 350 head castings were the same.

Want to know because I have 1 set of each and I want to port one of 'em. The 69 heads are ready to be started on but the 70 heads are still on the running engine..

[Mark Demko]

Im currently running a set of '69 350 heads, ported, bowls opened up for the TA big stainless valves. They look identical to my original 71 heads, and the set of 78 350 heads that are off the 78 350 block im running now with the 69 heads. 95% of the compression increase or decrease in the 350 motor came from the pistons dish, or lack of. In other words, no, you wont pick up a point or two in compression in the 350 motor just by switching from 69 to 70, or 71 heads, theres only a few cc's of difference, and I think thats probably from casting variables, it wasnt really designed that way.
The specs for the 350 heads from the NHRA website are as follows:
1969 51cc
1970 48cc
1971 50cc
1975 50cc
1978 50cc
The 3 different 1970 350 motors that Buick offered had the same heads cc's (48) But the comp ratio of the 260 (2bbl) and 285 hp (4bbl.) 350's was 9 to 1 (pistons had a deeper dish) The 315 hp motor had a piston with a VERY shallow dish, thus, the jump to 10.25 compression. Hope this helps:beer Mark

[GS69350]

I knew about the pistons, but I had heard something about the heads.. 3cc's will make a tiny difference, but for all the work I want to do that 3ccs will be worth it..

Now, to get myself a set of 68-70 10.25:1 factory pistons in standard size...

Dan