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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
I have a question concerning valve lash and valve adjustment. I just reinstalled the cylinder heads on a 2.8 L V6 motor… The tech manual says that I should achieve zero valve lash and then turn the nut one and a half turns. My question is about the valve lash – when exactly is that achieved? Is that when there is just zero up-and-down movement or do you tighten the nut until there's is no turn on the pushrod and then turn it down one and a half turns.
As they are right now – I snubbed the nut down until the pushrod stopped turning and then I turned it another one and a half turns. Is that too tight?
As you know – you cannot remove the valve covers on these engines without taking off the EFI… And I don't want to do all of that again.
Zero lash on a hydraulic lifter means you tighten up the rocker nut until the rocker just touches the pushrod and valve tip at the same time without depressing either one. The hydraulic lifter needs preload to work properly. The preload is roughly 0.060". That means the pushrod needs to be pushed down that much into the lifter.
1-1/2 turns is probably too much preload. Most people only turn 1/2 - 3/4 of a turn from zero lash. The hydraulic lifter has a wide tolerance. More than 1/4 and less than a full turn will work just fine.
Once the preload is set, move on to the next one. The lifter will bleed off and the pushrod will feel loose again. Do not tighten it again. This is normal.
What Alky said... "zero lash" is when the end play in the push rod is just barely all taken up.
I have no clue how many turns on the nut, corresponds to how much preload, in a 6-cyl. .050" is kinda ordinary, .060" obviously is within the thickness of a mildly thick sheet of paper from there, and is entirely reasonable. 1˝ turns sounds a bit much but I don't know. In a V8, ˝ turn is more normal. The turns vs .000" correlation is determined by the rocker arm ratio and the thread pitch of the nut. In a small block V8 (305/350) as an example, the rocker ratio is 1.5 and the thread pitch is 24 (the studs are 3/8"-24); 1 turn on the nut then is something around .070" on the lifter, meaning, ˝ turn is about .035" and ľ turn is a bit over .050". I'd expect that 6-cyl to be somewhat similar, in the same ballpark at least.
Technically, you could put a dial gauge on the back of the rocker and tighten the rocker nut until you get the proper amount of preload but like I already said, the tolerance doesn't need to be exact with hydraulic lifters.
Thank you AlkyIroc and SofaKingdom. I used your advice how to determine zero valve lash and then set it on the fire-1, fire-4 valve adjustment method.
She is running like a champ!
06-16-2017, 06:30 PM
