Whenever you buy used heads, what are some of the things I should check out before the purchase. I know to make sure they are level all the around, and use a feeler gauge. Also I know there are ways to check for cracks. Like spray something on the alluminum heads and used some sort of magnetic flux on iron. Any input on this would be awesome. Thanks guys.

 

best bet would be to take them to a machine shop to be inspected but sometimes thats not an option like buying off ebay etc...

 

Yeah man, I'd like to do that, but I can't.