You most likely have an aluminium head which expandes with heat and will vise up on the plug. If you think a broken plug is bad try bringing the plug out only to find that it brought the head threads with it. You should never remove any bolt from a hot aluminum block or head. It be very bad.
The hole for the spark increases in size when hot. I have no idea where you got the information it decreases, but it's wrong.
03-05-2008, 02:22 PM
NEVER NEVER EVER REMOVE ON A HOT ENGINE. 
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