valve lash adjustment

[eran tomer]

hello
i was watching this video:

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from about 8:15 the teacher says that for his hot rod he'd tighten the nut 1/4 turn, for his buddy's car 1/2 because he wanna outrun him, and for the nanny's 1 full turn. what's the logic behind that?

 

[Schurkey]

Pretty-much none. No logic at all. Lots of Monkey-See, Monkey-Do.

SOME folks want the lifter plunger near the top of it's travel, so it can't "pump up".

SOME folks want the lifter plunger near the bottom of it's travel, so it can't "leak down".

GM lifters generally had lots of plunger travel, and put the plunger well-down from the top, so the valvetrain could wear over one or two hundred thousand miles, and the lifters wouldn't be noisy or cause problems.

SOME aftermarket "high-performance" lifters have restricted plunger travel, so that when they're adjusted properly, they're near the top of the travel AND they're near the bottom of the travel. But these lifters cost extra, and they aren't really what a person would want for high-mileage use.

For the record, when dealing with hydraulic lifters, we're not talking about "Valve Lash Adjustment". We're talking about "Lifter Preload", since the valve lash is "zero".

 

[Supercharged111]

It's nothing more than an old hot rod myth. Maybe there was some truth to it way back in the day? But for any motor being assembled today with stock stuff, a full turn is what you want unless your desire is to have a hydraulic lifter cam with a solid lifter cam maintenance schedule.

 

[eran tomer]

problem is i opinions range from 1/2 to 1 turn.
i'll probably do 3/4

 

[GoToGuy]

Why not follow the guidance from the poeple that designed the Engine. GM specific service manual.

 

[Hipster]

I normally set them 1/2 unless it's a performance lifter where the manufacturer calls for something different. Years ago I ran into a set of Sealed Power stock replacement lifters that held the valves open at 3/4 turn. Backed them up to 1/2 and all was good. Even set at a 1/4 turn if you find yourself having to go back in there repeatedly usually something else going on. Cam going flat, roller on a roller lifter , lifter that is collapsed or the face is damaged on a flat tappet, stud pulling out, rocker nut that is backing off etc.

 

[PlayingWithTBI]

On this most recent Lunati flat tappet cam and lifters, I went a full turn. It wouldn't even start, the valves were held open. I went to 1/2 and it fired right up.

 

[Erik the Awful]

I couldn't decide on 1/4 or 1/2 turn, so I went 3/8. I'm such a dork.

 

[sewlow]

Too tight can result in problems such as...
- the valves may hang open causing them burn due to not being fully seated. Usually the exhaust side. Those burning valves can cause detonation. That equals holes in pistons. These computer-controlled ignition systems alleviate that by pulling timing via the knock-sensors. That kills power.
- valves not fully seating = loss of compression.
- excessive wear on the cam. SBCs have a bit of a rep for eating camshafts anyways. Not so much of a problem with the newer roller cams.
- bent push rods or mushroomed tips.
- hard starting.
Loose valves run cooler. That means a cooler running engine.
Set on the loose side, the engine will rev faster, smoother.
Could be why commentator talks about messing with his bud's settings?
Just one more reason why I work on my own damn vehicles! Lol!
The granny settings? Have no idea why someone would do that.
Maybe-e-e...rich widow? Future cash cow for a valve-train/cooling system/engine rebuild? Hmmm...

I like to set hydraulic lifters on a warm running engine. An old valve cover with a slot cut the length of the top just a bit wider than the socket will keep the oil in the engine, instead of all over the e/bay, the fenders, you, the ground, the JYD.
Solid lifters get set when cold, through the firing order. But that's a different discussion.

GM Service Manual recommends 1/4 turn after they stop tapping.
...and that's what I was taught, (*ahem*) decades ago (ouch) before I had ever read a factory manual, by a fleet vehicle owner/mechanic with 30+ years maintaining GM vehicles easily seeing 500,000+ before being retired.

Better to err on the side of loose rather than tight.

 

[Supercharged111]

Aftermarket lifters don't necessarily have the same travel for the plunger as factory. Spec for factory lifters is 1 full turn (not opinion). I'd have to math to be sure, but I believe the idea is to get it in the middle of its travel. I've set them between 1/2-1 turn and never saw a difference.