Quote:
Originally posted by Early_S_Man:
Like the distributor, spark plugs are easier to remove when the engine is warm ... because the aluminum expands more when hot than the steel body of the spark plug,
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it's true the alum threads expand with heat but they expand inward TOWARDS the spark plugs, making it even more difficult to remove.
when you heat up an internal thread, the minor diameter gets smaller.
for this reason, it is best to have the engine stone cold when removing or installing plugs