I was trying my best to keep away from this conversation for fear of
putting my foot in my mouth. If my memory of my materials and
thermodynamics classes has not failed me, this explanation is why cold
holes are small holes.
Think of this experiment from your college physics lab on heat transfer
and thermodynamics. Consider a straight length of copper tubing that
cold water has flown through for several hours. Measure the length and
diameter of the copper tubing. Now replace the cold running water with
hot running water. Measure the length and diameter of the tubing. As
expected, the copper tubing will be considerably longer after the hot
water has run through it. You will also notice that the diameter is
larger, also as expected. The metal has expanded both linearly and
radially. Hence, the copper tubing had a smaller radius when it was
cold.
The same holds true for an engine block. The expansion is not nearly as
dramatic in the iron block as in the copper tubing, but the same
principles still apply. The cylinder is just like the copper tubing, it
just has thicker walls. When the engine heats up, the cylinder gets
longer and its diameter increases. This is only a very slight change,
but it does change.
Hopefully this poor excuse for an explanation will help.
Happy motoring to those of you that have managed to keep the toys out of
the garage. To those of you in slightly cooler climates, spring is only
a mere 5 months away!!!
Safety fast,
Mike
|