O.K. my rebuilt 400m had a broke exhaust valve spring on cylinder #1 replaced both springs drove it and it broke the exhaust spring on cylinder 5 and 7. I talk to the builder and I am having it towed to his shop.He going to get the specs. on the compcam that he installed a friend of my said the.springs needs shimed even new ones the builder disagreed who's right? I didn't put new springs when it was built builder said cam wasn't big enough to require new springs.