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In a message dated 12/7/2001 5:46:06 PM Pacific Standard Time, gregsays@swbell.net writes:

<< .........that leaves only a dozen engine  starts to make during the
coldest months.  So, how important is it to have a pre-heated engine during
the coldest months?>>

All it takes is ONE to destroy your engine. The coefficient of thermal
expansion for aluminum (ie, the CRANKCASE) is roughly twice that of steel
(ie, the CRANKSHAFT). So if your crankshaft main bearing clearances are 0.00
at 70degF, then after a long enough soak to reach thermal equilibium at -10deg F,
the clearances have diminished to roughly 0.0006, too small to have
sifficient eccentricity ratio for an adequate hydrodynamic wedge to form
(assuming, of course, that the oil pump is moving any oil at all at that
temperature). And then there's the reduced diameter of the cylinders, which
could cause the end gap in the rings to close up completely and wipe out the
top ring or the cylinder choke (or both). And there's more. Of course, if
you're flying an engine close to runout, it may be loose enough to survive.
And after a few really cold starts, it'll probably be much looser.
Why not just accept the word of the engine manufacturers, who recommend
preheat below (I think) 25degF. After all, they do know SOMETHING about their
products.
Jack Kane

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