i found one sitting in my friends garage...been sitting there for years untouch...i want to get machine work on it, but i dont want to waste my money if the block is cracked, what are the chances that the block is cracked for a chevy big block 402? someone told me its slim.

 

Get it checked at a machine shop, they will clean it and check it for you. Not for free, but it's cheaper than getting the machine work done and then finding out it's cracked... I doubt that it will be, but if you have any doubts whatsoever it's better to check now and be wrong than to leave it and have it come apart later.