I no longer build my own Spitfire engines so I'm not sure what the
clearances are, but I have noticed something similar in the sound of the
engine during warm up. Last year, I ran some early season races where
the temperature was down in the 40's over night. Upon starting the
engine, I had a noise that was evidently piston slap until the engine
warmed up a bit. Once warm, no noise and the engine ran great. That
went away once the low temps warmed up during the summer. This year, we
only ran in the summer and the piston slap was never noticeable.
On 11/13/2012 6:37 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
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