Topic: I have oval pistons

[KRONUS0100]

got my 72 750k motor torn down.  pistons are oval.....................all 4 of them.
they measure 2.397 across the skirts, and measure 2.384 parallel to the wrist pin....meaning .013 out of round....and the #2 wristpin is totally buggered and out of spec, probabably trashed tits bore as well.not even gonna measure that.
need to borrow bore guage to find out how un square the bore now is.....as the #2 piston is badly damaged due to wristpin.
anyone know how far out i am allowed to be before a bore is absolutely mandatory?  if i have to bore, prefer to stay with the 2cd oversize if possible.....not a big fam of automatically goin all way to 850....cuts down on future rebuild.

[markb]

I'm not sure how much but I think all pistons are oval so that they compensate for the heat expansion differences because of the skirts and pin holes, etc.

[crazypj]

Completely normal.
 There is a lot more material at pin boss so it expands further.
 Try heating them to around 250f and check 

[KRONUS0100]

aha...................................so i may still have good pistons
will heat up with a heat gun and check

[Steve_K]

That is normal.  Will you post video of miking pistons at 250 degrees?  I am easily entertained!  crazypj is correct, pistons are cam ground or machined to be round when heated in the cylinder.  Measure at the skirts to check.  Compare to cylinder diameter for spec clearances.
Steve

[crazypj]

I was joking about the heating, it would be an entertaining vid though