Were they remanufactured heads or new heads. If the heads were remanufactured, the difference of the thickness that has beed milled off is causing noise. The rods are too long now and the valves are opening too far. I can't remember if it has adjuster screws on the rockers. If so, adjust the rockers. If not, they make a shim kit for the rockers. If you have any other questions feel free to ask.
Tuesday, March 4th, 2008 AT 9:55 PM