<VV> Piston Slap - Pin Offset

edward szuch egszuch at gmail.com
Sun Nov 3 21:27:54 EST 2019

Regarding the piston slap discussion.......
When you installed the new forged pistons, was there a way to determine if
there was any piston pin offset in the piston and if so, did you take this
into account when installing the piston on the rod?
The Chevy shop manual makes no mention of this because they always refer to
keeping rod, pin and piston as a complete set from the factory, which would
have the correct pin offset.
However, pin offset is very important for noise in particular and I know of
no engine that doesn't have some amount.  Pin offset tends to transmit
combustion loads more gradually to the skirt (cocking in the bore) and
minimize slap.
If you have a copy of Bill Fisher's "How to Hot Rod Corvair Engines" you'll
see a couple of paragraphs on the subject on page 58 (revision III).  It
says there is a 0.055" - 0.065" pin offset on the stock Corvair piston.  It
gives a brief sketch and instructions for ensuring the correct rod/pin
installation.  I'm not sure what your forged piston has for offset but it
should have some.
It only takes one of them to make noise and since I saw no mention of it in
your e-mail, I thought it might be worth consideration.
If you don't have the Fisher book, I could try scanning the page and
e-mailing it to you.
Hope this helps.
Gary Szuch

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