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Forged piston cylinder clearance?

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speedster356 Plastic not Classic Racing

1,624 posts · joined Aug 2002 ·

#820040
JE forged piston 92mm / air cooled, what sort of cylinder clearance. This is on methanol and track only.
Spyder-WISD 07-09-05 11.6s @ 125 MPH

Speedster-WISD Nats 05 14.4s @ 89 MPH

Jet cruiser-Coogee 22-09-05 900 deg C @ 110,000 rpm

Weaseling out of things is what separates us from the animals....................Except the Weasel.

dangerous 23 Windows of Awesome

5,901 posts · joined Jan 2005 ·

#820043
They should have a spec sheet with them, but i would like to see min .005".
Boost? probably up to .010"
westi wrote:That's mad Alan.

speedster356 Plastic not Classic Racing

1,624 posts · joined Aug 2002 ·

#820044
No boost Dave. Thanks for that.
Spyder-WISD 07-09-05 11.6s @ 125 MPH

Speedster-WISD Nats 05 14.4s @ 89 MPH

Jet cruiser-Coogee 22-09-05 900 deg C @ 110,000 rpm

Weaseling out of things is what separates us from the animals....................Except the Weasel.

Beetspeed Slammed & Awesome Dubber

75 posts · joined Nov 2004 ·

#820428
dangerous wrote:They should have a spec sheet with them, but i would like to see min .005".
Boost? probably up to .010"
Wouldn't you need to know first what type of forged JE it is? Excessive clearence (if its not needed, not saying it isn;t) would only give extra piston slap.
AFAIK, there are 2 kinds (material used), each with its specific expansion/clearence rate per mm or inch bore.
The manufactors (JE) info about those rates are on their website including the ring gaps, so no guessing needed.
'75 1303 'Renner' 2.2 T4 turbo

dangerous 23 Windows of Awesome

5,901 posts · joined Jan 2005 ·

#820445
Yes.
westi wrote:That's mad Alan.

dangerous 23 Windows of Awesome

5,901 posts · joined Jan 2005 ·

#820456
Please.


Here are the specs required for the two different materials.
You can use the JE pistons website to work out what you have,
but as mentioned in my first response, it should all be in the specs sheet that comes in the box.

http://www.jepistons.com/PDFs/TechCorner/SCPDrawings/piston_instrc2618.pdf

http://www.jepistons.com/PDFs/TechCorner/SCPDrawings/piston_instrc4032.pdf

I always run a little more clearance with air cooled, or with boost as stated in the instructions.
But in a perfect world it should be fine with the recommended clearance they list.

The extra clearance can make it harder for the rings to do their job,
but a clearance that is too tight can be catastrophic(sp?).
westi wrote:That's mad Alan.