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Original Message
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| RE: Clearance for forged pistons?!? |
| By John - 05/21/2002 5:22:14 PM; IP 142.177.77.103 |
| Well...all the old specs for forged pistons for "performance" engines are in the ball park of what you've found, however it is imperative to go with what the piston manufacturer reccomends. My TRW forged pistons call for only 0.0015 " clearance, but if you read the fine print, it says to allow an additional 0.001" for high performance applications. So, that would be 0.0025" That goes against any Ford spec I ever saw for forged pistons. Now, most machine shops actually bore/hone to the nominal size. For example, a 4" piston that's for a 0.010 overbore is enlarged to 4.010 and the clearance is whatever you get when you measure it after the work is done. Also, used pistons measure loose as the piston skirts get banged up and "bent in" a bit after they are intially used, so an additional thou of clearance is normal when you measure them. I'd say your clearances would be fine for a high rpm strip motor with original forged pistons, but a little loose on the street. |
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