I just sent in my cylinder head to get redone at a machine shop. They called me yesterday to tell me there were two cracks in the head. Is it normal to find cracks after 175,000 miles on a head with an original timing chain? I never had a problem with the engine overheating. The shop said there were cracks from the injector hole to the exhaust valve? And since I need a new head, what is a reasonable price to pay for a used head? I'm sure it doesn't pay to buy a core from the dealer? Just wondering if I could get some input? Thanks.