Because the fit of the plunger to the body is so close to provide an effective leakdown rate, it is very important that dirt, foreign particles and varnish be prevented from entering the lifter and that a continuous flow of oil is supplied to the lifter as explained in Section 10. In order to accomplish [...]

a. 1951 Buick Hydraulic Valve Lifters Function In addition to its normal function of a cam follower, each hydraulic valve lifter also serves as an automatic adjuster which maintains zero lash in the valve operating linkage under all operating conditions. By eliminating all lash in the operating linkage and also providing a cushion of oil [...]