Bore tolerances

Hi all,

When it comes to bore measurements, generally what are peoples max “wear limits” of a bore.

I have a new set of wet liners that are supposed to be “OE” standard. I measured all 4 liners in the X and Y axis at three different heights and they ranged from half a thou over all the way upto 3 thou. Out of Round varied from half a thou to about 1 and half thou.

This is for a road car with not crazy horsepower. What would be an acceptable amount over the specified bore and the maximum amount of out of round. I know that the liners aren’t clamped and it is an open deck block, so I can’t imagine that the clamping force of the head would distort the liner too much?

It is running forged high compression pistons with a 3.1 thou piston to wall clearance.

TBH, I would send them back, if they were supposed to be "finished" to bore, or the out of round prevents honing to size.

But if they were a little undersize, with the intent being to finish to size and there's the material there for it, that should be fine.

Either way, I would NOT run them as-is!

Anyone else want to chip in?

Thanks for the quick reply!

I am planning on sending them back as I don’t think that is an acceptable tolerance, especially for a cast piston.

Just want to know for future reference, what is the maximum you would allow oversize, taper and out of round?

I'm not really the person to ask, but I'd expect, at least, within a half thou' or so, if supposedly finished and honed to size. That's nominal size to tolerance +0.0005" and -0.0000"

Some of the chaps working on very high end engines may be less than a tenth of a thou'.

I would hope some comment, one way or the other?