[Fot] I have piston shrinkage

[Jim Gray]

They are forged Wiseco's
jg

-----Original Message-----
From: Duncan Charlton [mailto:duncan.charlton54 at gmail.com] 
Sent: Wednesday, November 14, 2012 7:44 AM
To: Jim Gray
Cc: fot at autox.team.net
Subject: Re: [Fot] I have piston shrinkage

Jim,
That's pretty surprising -- what is the brand of piston?  Cast or forged?

Duncan
(Texas)
1952 Morgan Plus 4 
Red #6


On Nov 13, 2012, at 8:37 PM, Jim Gray wrote:

> FoT
> 
> Tonight I was reminded of the reason you don't measure stuff in the cold.
In
> a hurry
> 
> to use my new measuring tools I shot straight out to the garage and
started
> my post season
> 
> measurements after the teardown. My pistons & liners look great so I was
> expecting everything to be 
> 
> well in spec with about 15 hours on them. I was horrified when I was
coming
> up with a 
> 
> consistent .008 -.009 clearance. I measured the surface temp of the
pistons
> at 59 -60 degrees.
> 
> So I boiled some water and soaked the pistons for a few minutes. They came
> out at 92 degrees.
> 
> The pistons grew .004" and puts them right in spec. That's a lot of growth
> at a 32 degree increase in temp.
> 
> The liners measured out the first time within .001 of spec for the most
part
> at 60 degrees.
> 
> jim g