I took off the fan,alt,belt that runs the water pump,alt,and fan-i did check the compression on a few while my compression gauge was ok(broke)and my highest reading was 180lbs of compression which according to burt would make it around 12-to-1---it seems to run solid other than that noise and i can't firgure out where it's at.iv doubled check wiring...it's good and i'm getting spark to the cyclinders-iv switched dist. to-i checked the fly wheel and pressure plate bolts---re ran the valves...-still knocks away no matter what.it does not get hot though even with mostly water in it-it blows out white smoke out the driver side.