Quote:

The only thing I didn't check, I've never checked and didn't know I needed to, was the crank counter weight to piston clearance.

This was a K1 Hemi 4.15 stroke crank and in the first motor I used it in we cut the counter weights down besause it needed so much weight taken off of it to balance it.

And then when I hurt the motor last fall I had it offset ground to 4.25 and Chevy journals. So with the 7.100 rod and shorter pistons there must have not been enough clearance. It would turn over by hand just fine

Oh No !
I hate to hear that.

This is what I came up with (after the fact):

CWmax = Counter Weight max dia
Pthick= Piston thickness below the pin
Pin = Piston pin dia
Rod = Rod Length

CWmax = 2(Rod - Stroke/2 - Pin/2 - Pthick - Clearance)
For example:

CWmax = 2(7.100 - 4.25/2 - 0.990/2 - 0.240 - 0.060)
CWmax = 2(7.100 - 2.125 - 0.495 - 0.240 - 0.060 )
CWmax = 8.36" dia

So the piston pin support area should not have been a problem if the crank counter weights are less than that. On a low deck with 6.535" rods it gets close. Typically counterweights are 7.5" plus or minus dia (mine are cut to 7.14" dia). But maybe the skirt?

8088765-Piston_pin.jpg (188 downloads)