When I worked for Headrick, we had a local telephone company that had inline engines in their fleet vehicles that all had the integral heads on them. Everyone they pulled off when they serviced the engines had the head cracked. They didn't even have to be magnafluxed to see the huge cracks in them. In the 8-10 years we did the machine work for them before they upgraded to the newer Astro Van, I never saw one single integral head of theirs that was reuseable. Most of the times the cracks were both external around the exhaust and intake area as well as the seats and chambers. As Tom said, the thermal expansion of such a large unique casting contributes to its demise. We had a large scrap pile of them also.
