11/26/2022 0 Comments Comp cam 350 sbc chevy marineThe actual clearance is not important as long as you perceive it without question or doubt. With the lifter on the heel of its cam lobe, back the valve adjustment off until the pushrod moves end-to-end with ~0.030" of free-travel clearance. Once the plunger seats against its circlip retainer, backing off the valve adjustment further will create free-travel clearance that you can feel with your fingers as you move the pushrod axially, end-to-end. Hydraulic lifters contain an internal plunger spring that will extend the plunger in the direction of the valve pushrod as the lifter is unloaded. Choose the method you prefer or that is recommended for you camshaft and then be systematic and maintain consistency throughout the process. There are several methods for adjusting valves. Any lifter that contains oil already will bleed down within a few minutes of adjustment. As long as the valvetrain doesn't "clack" when the engine is started, there is no cause for alarm or worry.ĭid these explanations adequately ease your concerns?Īdjust hydraulic lifters the same whether or not they contain oil. If the lifter rests higher on the ramp of the lobe when the engine stops rotating, the lifter will still collapse but will bottom out holding the valve off of its seat and the pushrod will be difficult to spin using your fingers. When this occurs, the valve spring pressure bearing down the length of the pushrod is relieved and the pushrod spins easily. As long as a lifter is low on the camshaft lobe ramp when the engine stops rotating, there is an adequate range of internal motion with respect to the lifter piston within its bore to allow the lifter to bleed down without the piston bottoming in its bore. The greater the accumulated wear between the lifter piston and its bore, the quicker that bleed-down occurs. Regarding the "apparent loss of lifter preload" based on the ease of rotating some of the pushrods after the engine sets overnight without running, hydraulic lifters naturally bleed down under valve spring pressure given a sufficient amount of time. It is far better to employ the proper spring and retainer combination to match the cam's profile, the valvetrain mass, and the engine's purpose, being mindful to limit engine RPM to a safe level. But, that sort of defeats the purpose of hydraulic lifters, and I don't condone the method. The key is consistency in the preload from valve-to-valve adjust all valves exactly the same.įYI - In some high-performance applications, a smattering of builders recommend zero lash, zero preload to eliminate the possibility of lifter pump-up in the case of valve float. Regarding the zero-lash hydraulic lifter preload adjustment, anywhere in the range of 1/2 to 1 full turn is suitable. The method you described works fine for a stock-to-near-stock camshaft profile.
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