Hydraulic lifters adjustment ???

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Hi,

It’s my understanding that valvetrain with hydraulic lifters shouldn’t need any adjustment regarding valve lash.

But I regularly stumble upon some workshop manuals for those engines that describe some valve lash adjustment procedure.

What’s the deal? I think I’m lost.
 
Up to the '70's there was an adjustment to put the lifter in the centre of it's travel. Later engines it was fixed...any work on valves and seats could take them out of the window.
 
It depends on the engine. They don't require it nearly as often as solid lifter designs, but some still need it periodically. Older Chevy engines, for example.
 
Hydraulic lifters need to be preloaded a little bit when initially set up. With hydraulic lash adjusters in an overhead cam set up, the preload is accomplished by the cam / roller follower / valve stem geometry and some lash adjusters are adjustable through the small oil hole.

In a typical American V8 "Small Block Chevy" type engine, on initial assembly you would crank down on the rocker arm nut while spinning the pushrod with your fingers until you can't spin the pushrod anymore and tighten the rocker arm nut another 3/4 turn and you're done.

Other American engines like Fords use a positive stop shoulder on the rocker arm pedestal that usually equals the proper preload when fully tightened. Various lengths of pushrods were available in case you ended up with too much or too little preload due to cylinder head resurfacing, etc but it usually isn't an issue with positive stop rockers.
 
On my race engines I adjusted them so I could just turn the pushrod with 2 fingers. Or just so the ticking stops if doing it while running. Definately more power that way, but probably have to adjust them more often.
I might go slightly tighter on a street engine, unless it was a sunday driver only type. Low miles per year.
 
Originally Posted By: ARCOgraphite
I only preloaded 1/4- 1/3 turn on my fairy cammed street SBC, Is this wrong?



As long as the lifter has enough preload that there is zero valve clearance "slack" at any time, they should be fine. 1/4 turn is a little on the light side and it won't allow the lifter to take up much wear in the rocker arms and pushrods like 1/2+ turn would.

You can adjust them while running if you tighten the rocker arm nut until the lifter stops clacking and go another 1/2 turn (or whatever) from there, but the factory never did it this way and it's messy and time consuming and unnecessary.
 
Originally Posted By: ARCOgraphite
I only preloaded 1/4- 1/3 turn on my fairy cammed street SBC, Is this wrong?



After putting a new, smoother cam in my Suburban's 350 (some dummy put a 3/4 cam in an otherwise stock smog-era engine) I found differing numbers, from 1/4 to 3/4 or maybe even a whole turn. IIRC I set mine to 1/4 and 4 or 5,000 miles later the valve train is perfectly quiet.
 
Originally Posted By: Silk
I've never seen any adjustment on hydraulic lifters or lash adjusters on an ohc engine.


This type of OHC lash adjuster (Ford) is adjustable with an allen wrench and they can be adjusted in place through the hole in the cam follower with everything assembled. This is something that hardly ever needs adjusting, though. If you have preload issues on an OHC engine that is anywhere close to stock, you have other more serious issues. The "sweet spot" on OHC lash adjusters is pretty forgiving with a big window of error engineered into them.
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(Images borrowed from the internet)
 
Ive seen Class-3 lever finger followers with stationary lash adjusters on mainly SOHC but I see Subaru uses this on FB engine now - last time I saw a cutaway.
 
Last edited:
Originally Posted By: Scdevon

This type of OHC lash adjuster (Ford) is adjustable with an allen wrench and they can be adjusted in place through the hole in the cam follower with everything assembled.


I knew someone would come up with something. I've never seen one of thoses, or if I have I have never had to adjust them. I don't like the term ''preload'' when setting hydraulic lifters, there is no preload, you are just putting it close to the centre of it's movement, to preload it you would be going beyond it's range.
 
Originally Posted By: Silk


I don't like the term ''preload'' when setting hydraulic lifters, there is no preload, you are just putting it close to the centre of it's movement, to preload it you would be going beyond it's range.


Well, you are depressing a spring and plunger in the valve lifter by tightening the rocker arm nut so preload somewhat fits. Preload doesn't necessarily mean overloaded or out of range.

It's just my visual observation that an additional 1/2 turn on the rocker arm nut doesn't place the lifter plunger anywhere near the center of it's movement. 10% depressed off of it's upper stop maybe at the most.
 
Did this thread go nowhere?

You have to speak to a specific engine to get somewhere on this subject.

OP work in a garage doing partial/full engine rebuilds?
 
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