the first time it bent an exhaust valve idk what caused that. i had not touch the motor except to tighten the two bolts for the cam cover. the second head i was told the keyway broke off and caused the cam gear to jump and that is what loosened the bolt for the cam gear. when it jumped timing i bent both valves, 98 i had her torqued right but she came loose after the keyway broke off, huge relief for my ego lol. i ended up taking her to our local shop and said i want it done right and a warranty 400 and 15 dollars later i got 5 hours of labor, new valves, retainers, guides, new float needle, and new gasket set. and she runs like a champ now. i ll get over there later today and get some goode pics once i wash her off from last lol