Piston Size - 64.42mm?

[tOj]

I just recently picked up a 96 motor. took the head off on the pistons it reads 64.42 (mm) I'm trying to figure out what bore it is on. I was pretty sure that 64.50 was .020 over, so what the hell is mine? Just wondering, I'm glad it's under .020 over... just wondering what it is.

[fast87]

yours is .020" over, i measured my pistons with the same measurements, on brand new wiseco's...i think they do it slightly smaller to ocmpensate for piston growth, which i heard is 2 and a half thousandths(.025") need any more help LMK, i just honed and measured out 2 sets of cylinders and a new piston set..all .020" over(but one set was .08" too damn much...bought off ebay, seeing if i can return them...be careful buying jugs off ebay)

 

~Mark~

[reknelb]

My experience with wiseco's = EXAMPLE; If you order 70mm pistons, your bored and honed hole will end up being 70mm, and your piston will be smaller by the amount of the recommended clearence.

 

I ran into this problem once. I had a pair of cylinders that measured about .003" over 65.5mm. I called wiseco and asked if thier pistons were exactly 65.5mm OR if they were smaller. They said they would measure exactly 65.5mm. Well needless to say when they came they measured about .003" under 65.5mm. That would have given me about .006" clearence, so i sent them back and went next size up and had the holes opened.