Description
The preload (pre-tension) of the hydraulic valve lifters is crucial for the proper operation and longevity of the camshaft and valve lifters. When rebuilding a V8 engine, the preload can be changed, for example, by surface-facing the cylinder heads and installing a different camshaft. Adjusting the preload of the valve lifters requires shims that are mounted under the rocker shafts.
The location of the oil supply hole in the shim is also very important; the rocker arm shaft receives oil from the front of the cylinder head. This hole in the shim should be located at the top of the rocker arms.
Two shims also have a smaller hole; this serves to limit the amount of oil flowing to the rocker arms, if necessary. This could increase oil pressure in the case of worn rocker shafts or when using adjustable, aftermarket rocker arms.
Currently we only have a shim set in the thickness of 1.5 mm.