margaritaman, is very close on his startup,
Having been in the machining trade almost 50 yrs. there are growth differences in how metals grow and contract.
example: STEEL grows approx (.0001) per 10 degrees temperature change.
example: ALUM grows approx (.0007) per 10 degrees temperature change.
But other factors come into play, such as copper head gaskets, alum rockets, steel blks, alum heads etc.
Most solid cams set between .020 and .030, so the best method is too always set them loose, maybe .030 warm the car up to running temperature and reset them correctly and never run a car on the initial setting.
margaritaman is right about the blower belt tightening up and nothing will eat an idler pulley bearing or break a blower belt quicker than a overtight belt.
just my .02 cents
Zip.