Today I received my new standard bore hi-comp pistons and was surprised how much movement the have in the bores.
I realize that these pistons are cam-ground, measured under the pin and they were .020" smaller then a measurement taken 90 deg from the pin per the box instructions. This really makes them rock in the bores.
I know the rod will keep them in-line so is this really an issue or should I be concerned. Bores are no more then .002 out of round and measure around 3.753".
Cam ground pistons are always that way.
They will get round when they warm up.......
I have a 26-27 block that has been sleeved and fitted with standard aluminum pistons. I have a set of standard aluminum high compression pistons, that I just for grins, tried one in the bores from the top. It fits with such little interference that I wonder whether they would seize, if used.
In a fresh engine you would hone the bore to fit the piston. So if the thrust diameter of the pistons is less then .004-.005 clearance to the wall, then there might be a good chance of locking up.
Mark, I haven't checked, but I hope the diameter of both the regular and the hi compression standard aluminum pistons are the same. The regular pistons are already assembled in the block by a noted engine builder. The hi compression pistons will slip into the top of the sleeved block, if held perfectly square and centered to each bore, but just the slightest tilt of the piston when inserting into the top of the bore will let you know the piston is not square with the bore. After inserting into the bore, the piston won't fall if dry, but will if a little lubrication is used.