(besides i think 1970 stage 1 @ 61cc)
the 'regular' 1970 head is exactly the same as the Stage 1 head out of the casting mold. they even have the same casting numbers.
the difference arises, not because of the head architecture, but because the Stage 1 heads are cut for the larger Stage 1 valves. the larger Stage 1 valves occupy more space *INSIDE THE COMBUSTION CHAMBER*, reducing combustion chamber volume and thereby bumping static CR by that 1/2 point that you see in the factory spec sheets.
so the answer is, have your machine shop cut your stock 1970 heads for the larger valves. that's what the factory did.
I got these heads because i thought they had the highest compression and only to find that 67-69 had the highset
not sure what you're talking about here. all of my info shows that the basic 1967-70 heads all had ~69cc ( factory production being fairly sloppy in those days ) combustion chambers. the 1970 Stage 1 has 66cc. larger Stage valves weren't installed in 1967-69 because the bore size in the 400 is far too small and gets serious valve shrouding while the 430 only sees marginal improvement.
71-74 open up slightly to 71cc and then 75-76 get monstrous huge ( relatively ) with 78cc chambers.
75-76 pistons have a smaller dish than 71-74 pistons but the word is that the pin height is also shorter which just means that the overall combustion chamber size is the same, there's simply no squish area around the perimeter of the 75-76 pistons. which is bad.
additionally, the 67-69 heads have several minor variations with the way things are done in the 455. they can still be used on a 455 block ( and vice versa ) but you need to be aware of the considerations.
http://www.1badriv.com/knowledge.htm
but then, if you want to get the REALLY serious heads you'll find yourself a set of Stage 2's.
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