302 piston question

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Sep 17, 2009 | 07:17 PM

dorymate88

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Joined: Apr 2002

Posts: 55

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From: New Brunswick

302 piston question

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

Sep 17, 2009 | 10:03 PM

Conanski

FTE Legend

Joined: Jun 2006

Posts: 31,930

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From: Ottawa, Ontario

Quote:

Originally Posted by dorymate88

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.

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.