I'm curious what are the signs of a bad lifter, I'm trying to track down what seems like more valve train noise than what I would expect in a recently rebuilt motor. Sounds find at idle and revving while I'm under the hood, pretty much like a throaty tractor, but I'm hearing 'something' when I'm driving with the window down and I go past a wall or another car is next to me and bouncing the sound back. I've checked the valves, and recently did some valve train work, so I think the top end is ok. My second suspect is an exhaust leak.. Thanks.