The two rear bolts nearest the firewall LH side ( and maybe someothers) holding the heads ARE NOT BUDGING with my impact driver, so I was considering using a cheater bar to remove them. Im not a full time mechanic and Im hoping that will work and not break the bolts. Anybody have an opinion on that issue? I hit them hard with a chisel to release tension on the threads a couple times. Ill try that again before twisting them again. The one in the head is partially submerged in oil so it probably pretty wet. They've not been removed in known history before. Engine is in vehicle, a '95 4.2L.