NHRA piston guide,
69 440- .027 below deck
70 440. .051 below deck
71. 440 .051
72. 440 .123 below deck
67 440 .059
68 same as 69
NHRA specs are not ACTUAL FACTORY and should not be used as a guide for any spec that is Factory as delivered mopar related.
So they just pulled those numbers out of the hat? Whitch one do you think is wrong?
Just did the NHRA allowed pistons, 68-71 use same piston but show different ch? Should have checked what head gasket they allowed.
I don't know where they get them, Chrysler maybe ?? But I know that a 69 440 piston is not .027 in the hole , it's more like .050 in the hole.
For some reason Chrysler piston spec is .020ish HIGHER than actual. Perfect example is a 68-69 383 HP, the factory piston on blueprint spec is .0025 in the hole ... CH is 1.932 ..., NHRA spec has the piston .021
ABOVE the deck. There isn't a 383 delivered from Chrysler with a piston that high above the deck surface.
Also the NHRA spec for a 906 is 79.5cc chamber, ACTUAL is 90-92cc.
Advertised compression ratio from Chrysler on the 383 is 10.0, actual is 9.2, built to the NHRA allowed spec of 79.5cc , +.021 deck and .070 max overbore yields close to 11.5 ...
