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I'm sure a head change will yield some increase in compression, but with worn bores and rings I gotta think blowby is going to be increased greatly. So, how much additional compression is he really going to get?



Judging by where and how this is bouncing all over the place you are just adding more facts that are confusing the issue and I don't think it really matters, if I'm reading this right getting any work done outside of just bolting on parts to the shortblock as is is the only course of action ?

There isn't a piston that will swap directly in that's not going to cause havoc with the rings and the current ridge, that's an issue being ignored.

One thing that is been glossed over is no 440 piston is going to fit a standard bore 400 because the standard bore of a 400 is 4.342 , thats .022 oversize .