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Alright, my method for adjusting hydraulic lifter preload/valve lash has always been what is commonly regarded as the correct way..... tighten rocker arm nut just until the point that all play is removed from the pushrod and the rocker arm, then continue to tighten the nut from 1/2 to 3/4 of a turn.
My 1988 Corvette Service Manuals showed up yesterday and I was just flipping through when I came upon Installation and Adjustment on page 6A1-7. It states to tighten the rocker arm nut until there is no movement of the push rod...… nothing else, no additional turning mentioned.
Can anyone verify if this is a mistake in the manual, or have I been adjusting hydraulic lifters wrong for years??
Jared
Last edited by lotsofspareparts; Jul 16, 2019 at 01:19 PM.
there's so much latitude in (lifter) valve adjustment - probably, anywhere from 1/4 turn to 1-1/4 turn from zero lash. in a perfect world, the idea is to get the adjustment approximately half the lifter's plunger travel and a consistent adjustment across all 16 lifters. I don't set zero lash, but set lash at .001" then 3/4 turn, across the board. sequence per FSM. I don't know the factory plunger travel for a typical GM lifter, but the number I most often see is .060"
(my 2-cents) while it doesn't hurt anything - going through all kinds of special sequences, finding cam lobe base circle, and adjusting on the fly, in reality, is pretty much an exercise in futility.
I just happened to have my 86 FSM open to that exact page from yesterday as I will be going through those adjustments after replacing my valve seals later today. What Joe said is right on. I think the discrepancies in what the FSM calls for exemplifies that point. For example, you said your 88 FSM calls for 1/2 to 3/4 of a turn more after removing lash, and my 86 FSM call for one whole turn.
I always follow the book for my specific car. I've never had an issue going that route.
Correct Valve Lash Adjusment???
