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This tech paper will discuss the adjustment of Chevrolet hydraulic lifters (“valve lash”). The procedure outlined here differs slightly from the Service Manual, and is based on my years of experience doing this work in the quickest, least painful, most economical way while keeping the level of quality high. It is recognized that other people will have different methods of doing things, and may disagree with specific methods and procedures that I use. Without the use of hydraulic lifters (mechanical lifters), the valve train must be adjusted with a certain amount of “slop” in it (“lash”). This lash is necessary, since the various components in the valve train tend to “grow” and expand as they heat up from normal engine operation. As the components “grow,” they take up a large portion of the lash, but some lash must still be retained as a safety margin. If there were no lash, there would be a risk of the valves not closing fully, resulting in poor engine performance and burnt valves. This lash, however, results in a bit of valve train noise as parts “clank” together, and this clanking induces wear of the valvetrain components. When the hydraulic lifter is at the “low” point in its bore (the valve is closed), the body of the lifter is exposed to pressurized oil in the lifter oil galley. The lifter body has a little hole in it, and this hole allows oil to enter and/or exit the lifter body. The pressurized oil in the galley thus enters the body of the lifter, and pushes lightly on a plunger in the roof of the lifter body. This plunger is about a half inch in diameter, giving it a total area of approximately 0.12 square inches. So for a performance application, we split the difference. A ½ turn lifter pre-load will raise the rpm limit of the engine, yet it will still provide quite a bit of plunger travel so the lifter can do its valvetrain wear adjustment thing.. It will also keep the plunger away from the snap ring retainer, and it will keep our operation safe. Safe, reliable, improved performance and good durability/life: what more could you ask for?
Tags : poor engine performance, hydraulic lifter, hydraulic lifters, train noise, valvetrain components, valve train, performance application, safety margin, little hole, square inches, plunger, large portion, galley, slop, bore
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