Yes, the factory heads are known to crack. However, rarely does the cracks ever cause a problem. There are so many of these magnums with 250,000 ++++ miles and still run excellent, and most probably have cracked heads. Of course, EQ would be better as they are less likely to crack, have a little better ,,, Mine are bare. Im pretty sure he said that the assembled ones are oem and that if I put my stock ones on it they would work for a .501/.513 lift camshaft. Is this true ?