Number on piston

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Feb 4, 2011 | 04:53 PM

rdweathers

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Joined: May 2010

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From: Florida

Number on piston

Going through my engine and I see 040 stamped on each piston, does this mean it has been bored out this much more over factory specs? It is a true 390 and not a made over 360 which i am glad to figure out. Thank you.

Feb 4, 2011 | 04:59 PM

Fordman18

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It means your engine has been rebuilt. The cylinder walls have been resurfaced and they put larger pistons in to fill the space. It's punched 40 over or forty thousandths, however you want to say it.

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