Piston side wall clearance???
Thread Starter
Burning Brakes
Joined: Dec 1999
Posts: 924
Likes: 1
From: Houston Texas
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
4.1531
4.1531
4.1532
4.1535
4.1539
4.1539
4.1539
4.1547
Mark
Race Director
Joined: Sep 2000
Posts: 17,298
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From: The Top of Utah
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!!!
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!!!
Race Director
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From: Corsicana, Tx
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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
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
Le Mans Master
Joined: Mar 1999
Posts: 6,744
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From: delmont pa
Cruise-In I Veteran
Cruise-In II Veteran
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
Instructor
Joined: Sep 2001
Posts: 171
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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.
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.
Thread Starter
Burning Brakes
Joined: Dec 1999
Posts: 924
Likes: 1
From: Houston Texas
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
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
