I have a 2000 chevy tracker, I installed a rebuilt head, but am gettin a loud ticking, valves are hitting pretty hard. I had put this rebuilt head in another motor, about 9 months ago, I started it and I found out the lower end was blown, (prior owner ran it out of oil. It ran for less than a minute. So it sat for that long. I put it in another one that I let overheat and warped the head on it. I tore it down and put this fresh head in it. I just tested oil pressure and am getting over 80 at 4000 rpms, I have driven about 60, maybe more miles in but still the oil hasn't reached and filled what i am suspecting to be air pockets in the head. Should I keep driving or as I have seen on another post/answer use some mystery oil and hope that will help my delima. I remember having the same problem on this car the first time, it took some time, but it went a way also. I don't remember the valves hitting this hard though. Any advice. Bill