200 6cyl '68 - when at speed 65-70 mph with light gas pedal the engine will begin to tap or knock. if you shower down past 70 the knock goes away as long as you continue to accel or if you back down below 65 it disappears. head has been redone too many times to think about. no spacers or multiple head gaskets used...can anyone think of what the knock is ? I'm planning on replacing the head with one that hasn't been shaved, but obviously would love to know if this is going to solve the problem. will also replace the oil pump when I tear it down (could the knock be oil starvation at speed ?). don't really want to get into rebuilting the bottom if I don't have to.