Yes I have low compression on the motor backed off on rocker shaft and the compression came up, so apparently someone did a valve job, or shaved the heads, or shaved block I don't know. I bought the car this away just finding out this when I put a cam in her. Doesn't smoke or burn oil so I want some roller rockers to adjust valves one by one. the stock rockers have a off set to the left on eight rockers and to right on eight rockers. So straight rockers will not work because it changes the geometry of the push rods, if anyone has been inside of a stock 340 72 and I know a hole lot of u guys have they will know what im talking about, and yes I know I can remove the heads and redo the valves but trying to advoid that. I have found out they don't make these any more unless u want to pay 1200-2000 for them