As found in a cam-in-block engine, lifters are responsible for transmitting the movement of the camshaft lobes to the pushrods. The pushrods actuate the rocker arms, which open the valves. Hydraulic lifters allow the valve lift to increase with engine rpm by filling up with oil as the oil pressure rises. The oil inside pushes the rocker arms further away from the camshaft, which causes the valves to open further. Oil pressure failures are usually at the root of lifter tapping, also known as lifter collapse.

Step 1

Check the oil level. If the oil level is low enough, the oil pump may begin to suck in air at high RPM, thus starving the lifters of the required pressure. If the oil level is too high, the rotating crankshaft and rods will splash into it,…