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Re: piston/bore clearance when using forged pistons

To: fpspitfire37@msn.com
Subject: Re: piston/bore clearance when using forged pistons
From: "SHANE Ingate" <hottr6@hotmail.com>
Date: Sun, 11 Jan 2004 08:50:18 -0500
Aaron Johnson asked:

>What would everyone recommend for piston to bore clearance when using
>forged pistons?

It could depend on who's pistons you use!  8 year ago, I observed a test
on Cosworth and JE pistons.  Heat was applied to the 2 pistons, and the
JEs swelled twice as much as the Cosworths.  I do not recall that actual
measurements.  Sorry.

It was explained to me that the Cosworths had better metallurgy, with a 
lower
coefficient of expansion (or something like that).

What this means is that piston bores for these JEs had to be larger than for 
the
Cosworths, meaning more piston slap when the JEs were cold, with subsequent
increased wear, etc, etc.

Having told that story, this is now ancient history.  JE have fixed this 
problem
and perform equally well in this test as the Cosworths.  However, it does 
apply
to manufacturers of forged pistons that use inferior metallurgy.

Shane Ingate, JE & Carrillo rich but $$$ poor, in Maryland

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