I was installing .040 over pistons, and the third one I did did not want to go in the bore. It turned out that one of the little tabs at the bottom of the piston skirt was somehow hanging up. After a few rounds with a file
(and plenty of cleaning), the piston does go in, but it is a very slightly bit
tighter fitting than the first two pistons feel. It rotates freely in the bore (grabbing the piston head and twisting), so I believe the bores are round.

SO the questions,
how much slack should there be between the skirt and the cylinder wall? I have never seen anything about measuring this.

Is this filed piston safe to use? Has this happened to some of you?

Thanks and Peace

Did you install the pistons by the number stamped on the rod or might have been written on the top of the pistons by the machinist??

Richard

_________________
Part of Tyrde-Browne Racing

.001 to .002 clearance is about right for a cast piston... more for a forged or Hypereutectic (sp) piston.

I would try that piston in a different bore to see if you get a better (looser) fit.

To be honest, a good engine builder (and the factory) measures, sorts and "matches" the pistons with the bores so they end-up with the needed amount of clearance.
DD

I am installing based on numberr on connecting rod. I was with the machinist, and we did not test fit pistons before installing on con. rods.
THis is going to be a daily driver, not a racer, if that matters.

all other pistons seem to have just a tiny bit of wiggle in their appropriate cylinders; the one in question has just a tiny bit less. Its more like snug.

Bores are pretty uniform diameter top to bottom, doesnt seem to be a taper, based on measuring the gap in an oil ring placed in the bores.