Spec for piston to pin fit


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By 46yblock - 15 Years Ago
Can someone please give the specification?  I have a set of like new shiney cast pistons, with three that seem to have pins which are too loose.  The pin slides through the piston at room temperature, only hanging up out toward the clip locations. 
By PF Arcand - 15 Years Ago
If you have a Ford shop manual, the specs are there in the engine dimensions section. Anyway, the 1957 book says, piston to pin clearance is 0.0001-0.0003 thousands. Limit is 0.0008 thou. There were 0.001 & 0.002 O.S. pins originally available. Now ?. Std pin diameter was 0.9120-0.9123, originally coded green. O.S. were coded blue & Yellow.
By 46yblock - 15 Years Ago
PF Arcand (6/10/2010)
If you have a Ford shop manual, the specs are there in the engine dimensions section. Anyway, the 1957 book says, piston to pin clearance is 0.0001-0.0003 thousands. Limit is 0.0008 thou. There were 0.001 & 0.002 O.S. pins originally available. Now ?. Std pin diameter was 0.9120-0.9123, originally coded green. O.S. were coded blue & Yellow.

Thanks for looking that up Paul.  My '56 manual has been in loose leaf form quite a few years, so is in three different places.

Very recently oversized pins were offered on ebay.  Dont think they sold, but werent relisted either.  Does anyone remember who was offering them?

These pins dont look worn at all.  But someone has worked over the pin bores.

By Speedbump - 15 Years Ago
I don't know what equipment you have available but the true answer to your question of how much you have can be answered by using, or find a shop with, a Sunnen AG-300 guage and a pin fixture.  If you go to oversize, you will need their services anyway for proper pin and rod fit.  I personally wouldn't be afraid of a pin boss that was .0005 or so as long as they were all the same AND round.  I'm not a big fan of those pin clearances that get down to the .0001's and 2's, but that's just me. 
By aussiebill - 15 Years Ago
46yblock (6/10/2010)
Can someone please give the specification?  I have a set of like new shiney cast pistons, with three that seem to have pins which are too loose.  The pin slides through the piston at room temperature, only hanging up out toward the clip locations. 

A guy has .002 and .003 oversize pins on Ebay $2.75 each, # 230437733069 Regards bill

By John Mummert - 15 Years Ago
Mike, I set up cast pistons for a street engine at .0004. Race stuff is in the .0006-.0008" range. Some guys go as much as .0010" for pure race stuff but you will probably be able to hear them at that clearance.
By 46yblock - 15 Years Ago
Thanks everyone.  I am counting on these pistons!  .080 OS 292 with cylinder bores found good to go.