Tore open a 89 302 and the pistons have a 030 on top, i am new to rebuilding fords so i gotta ask whats it mean.

I have done chevv builds in the past and had 60 over stamped into pistons.

Just curious and want to make sure i get the right ring set.

Thanks

 

So you're saying the Chevy pistons had the words "60 Over" stamped right on them? If so that's freakin hilarious.. I mean I know Chevy guys aren't the sharpest tool in the shed but that's too much. I'm not calling you a dim wit it's just funny you found that in a Chevy motor.

OK.. now that I had my fun I'll let you in on the big secret. Machine tolerances are often measured in thousands of an inch, the standard bore diameter of a SBF is 4.000" exactly, 30 thousands over is 0.030 and is called 30 over for short and when you add the two you get a total bore of 4.030". In the same way 60 over would be 4.060.