how to measure pistons ??

[Alumarine]

Reason I ask is I took my pistons (still attached to rods) to a machine shop to get a second opinion on how one of the wrist pins felt. The guy took them back to his machinist and said well the wrist pin bearings are fine but your pistons are badly tapered. He said they had .006" of taper which was out of spec.<br /><br />I measured the pistons perpindicular to the wrist pins and got 3.97" 3.99" and 3.99" top middle and bottom on all 4 pistons????<br /><br />Am I doing this wrong?? Pistons look great and the rest of the engine spec's out fine.

 

[MrBill]

Re: how to measure pistons ??

He is able to measure to thousandths, you're measuring hundredths. Your top measurement shows taper at the top as he suggests...either way the pistons are tapered. His degree of accuracy is ten times your equipment capability. You'd nee to check manual for acceptable tolerances...but my guess is any engine that old is probably a lot worse.

 

[Alumarine]

Re: how to measure pistons ??

Thanks MrBill. I actually have the official merc manuals for that motor and they don't give any spec's on the pistons. It does show tolerances for the cylinders though.<br />I'll get a micrometer and check it again.