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derbyguy583 03-15-2007 07:59 PM

Chevy Head Casting numbers need help identifying
Hey guy's I have a set of heads I want to have redone and put on My Demo derby Motor I need help figuring out if they are a matched set and what size valves they have in them.Any help would be greatly appreciated. The numbers off of them are Left Side 3973487 also C101 & GM27. Right Side 3973487X also A132 & GM27 Once again any help would be appreciated thanks. Jacob

derbyguy583 03-15-2007 08:00 PM

Re head Numbers
Hey guy's by the way these are off of a small block Chevy Thanks Jacob

F-BIRD'88 03-15-2007 08:10 PM

many, but not all f the old SBC heads that had a "X" at the end of the casting number, had a slightly larger intake port.
the 487(X) heads came on 350's and 400's. the 400's had 1.94x 1.60" valves and extra "steam holes" between the cylinders on the decks. The 487's that cam on 350 could have 1.94x 1.50" valves or 2.02x 1.60' valves. the chamber size varies from 76cc to 80cc. They only way to tell if the two heads you have, have the exact same chamber size is the cc them. Ya can't tell by looking at them. But if they have different valve sizes say 1.94x 1.50" in one had and 1.94x 1.60" in another that might be a clue. You could equalize and eliminate any difference in port size by porting the heads. and replacing the valves so they match if that is important to you.

Rogers Performance 03-15-2007 10:24 PM

Most of the 487x heads i seen came off the 71 LT1 corvette 2.02 x 1.600 valve.

NDNslicks4me 03-15-2007 11:07 PM

ya, a kinda rare head, not really for a demo derby car, no sense in cracking them if the rad gets busted

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