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I have them in my 69 383 also. Like he said, make sure ring end gap
is gapped correctly or you will break top ring. Also, if using the 906
heads which these are what those pistons were basically made for. Your
pistons are as close to "zero" deck as possible. Zero to get any kind of compression at all! Or even a few thousands above the deck wouldn't hurt at all. That's providing you are using the 906 open chamber heads.



Do you mean make sure the pistons are as close to zero as possible ? Because the KB pistons are .024 in the hole by design.

If they made the kb400 because of 906's they did it WRONG , they make a step head piston for the 440 and the 400 to work with open chamber heads but instead they put a flame travel RESTRICTING dome on the 383 ??? They screwed up wit hpiston design for big block mopars in general and the 400 was a poor attempt to correct it.

The kb400 will make the engine 10.0 if you put it at zero deckand that's not a good idea with open chambers heads unless you have 100oct available at the pump i would think , I'll be finding that one out shortly , but I used a flat top and cut my heads to get 10.0 ...