Piston side wall clearance???
My SRP "Forged High Silicon" pistons call for a .002-.0025 side wall clearance on street cars. The card from SRP says this clearance is built into the pistons, however my measurements only confirm that 4 of the pistons have this built in tolerance for my 4.1555 bore. I've listed the piston skirt measurements below for all 8 pistons (measured multiple times and at the correct skirt location). I guess my question would be is this range typical of all pistons or just the SRP pistons?
4.1531 4.1531 4.1532 4.1535 4.1539 4.1539 4.1539 4.1547 Mark |
Re: Piston side wall clearance??? (81vette)
I don't know if the deviation you have displayed is "typical" or not. I DO
know that final cylinder finishing and sizing SHOULD only be done with the pistons on hand so the machine shop can "precision" fit the pistons to each cylinder. RACE ON!!! |
Re: Piston side wall clearance??? (CFI-EFI)
I agree w/ CFI-EFI. Have your machine shop custom fit (and make tolerance) for each piston, no 2 pistons will be exactly the same.
Marck |
Re: Piston side wall clearance??? (81vette)
Mine had about .0025 built into them. I wanted them at .0045, so we put her back on the hone 'till it was right.
The SRP's are designed to be able to run a little tighter than normal forged ones, but I preferred a little looser. Just as a side note, they are dead quiet even on cold start-up in the 540. JIM |
Re: Piston side wall clearance??? (81vette)
SRP is(was) part of JE and GM bought JE a special compuer controled milling machine to do the 502 marine pistons for GM. that is why they are such close fit because of the shape. i have use JE pistons in a 4 cylinder race engine with a 3.500 bore and fit them at .0015. :chevy
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Re: Piston side wall clearance??? (81vette)
My SRP "Forged High Silicon" pistons call for a .002-.0025 side wall clearance on street cars. The card from SRP says this clearance is built into the pistons, however my measurements only confirm that 4 of the pistons have this built in tolerance for my 4.1555 bore. I guess my question would be is this range typical of all pistons or just the SRP pistons?Mark Ah, don't know what is correct/normal, can just tell you what I noted. My SRPs varied .0002-.0003". Mine had about .0025 built into them. I wanted them at .0045, so we put her back on the hone 'till it was right. The SRP's are designed to be able to run a little tighter than normal forged ones, but I preferred a little looser. Just as a side note, they are dead quiet even on cold start-up in the 540. SRP is(was) part of JE and GM bought JE a special compuer controled milling machine to do the 502 marine pistons for GM. that is why they are such close fit because of the shape. i have use JE pistons in a 4 cylinder race engine with a 3.500 bore and fit them at .0015. |
Re: Piston side wall clearance??? (arnold)
That's my son Arnold. Thanks for the kind words. :)
Thanks for all the replies. The variance of this set of pistons is greater than I expected. They should all have been around 4.1528 +- .0002, but maybe I'm expecting too much. So far everything else looks good. I think I'll call SRP to see if this variance is normal in their pistons. Mark |
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