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hydro lifter preload ?

lifter preload

  • 1/2 turn

    Votes: 10 83.3%

  • 2/3 turn

    Votes: 1 8.3%

  • 3/4 turn

    Votes: 1 8.3%
  • Total voters
    12
  • Poll closed .
sweetk30

sweetk30

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whats the average happy spot you guys have found for hydro lifter preload in a sbc/bbc engine all stock . ?

i have to set the preload on a engine i have they were backed off on for storage .

i have heard anywere from 1/2 to 3/4 turn whats your opinion .

engine is a 366 bbc for my dump truck spins maybe 4k rpm max if that even .
 
Last edited:
I prefer 1/2 turn ,

There are some guys I know that will do 3/4 to even a full turn to take some of the travel out off the lifter for more top end stability.

I think preload is less important then making sure the rocker tip is centered over the valve stem
 
Like Gus said, mostly I’ve gone 3/4. Different lifters may adjust different, but the feel at the rock and rolling the pushrod doesn’t change
 
When GM says 3/4 to 1-full turn I think they where talking about lifters that where pumped up full with oil. A dry lifter should need only 1/2 a turn.
 
I had some issues when I did full turn so I started doing 1/2 turn, haven't had issues since
 
Same here,I followed the specs GM listed , 1 full turn,a 1/4 turn at a time ,allowing several seconds for the lifter to bleed out and prevent a valve from hitting a piston,but I found the lifters wanted to pump up and hold a valve open after a high rpm blast,causing a dead cylinder feeling at idle for a minute until they bled down again.. ,so I backed them off to 1/2 a turn and then they didn't pump up unless you really wound the piss out of the engine ..
 
SBC lifters need about .020 to .060 of preload.
Depending on thread pitch on the rocker studs, one full rotation is about .080-.125
So zero lash plus 1/2 turn gets you in the sweet spot..

you could set up a dial indicator on one rocker....zero lash it, turn the nut one complete turn to see how much it moves on your engine...

Then you would know how much
a 1/4-1/2-3/4 turn will give you.

but for ballpark estimate...roll the lifter to base circle of each cam lobe, half turn after zero lash, and then put the valve covers on.
 
I'll add it is very important to be patient when adjusting lifters,that "waiting period" for them to bleed back down after you do a 1/4 turn is critical,you can make a valve touch a piston if you don't wait long enough..with oil flinging everywhere,smoking on the exhaust manifolds,even when you use deflector clips or a cut open old valve cover,you tend to want to get it over with quickly,that can be a disaster in the making..

I have adjusted the valves by using the procedure in a Motors or Chilton's manual by spinning the push rods at TDC until no play is felt and they just stop turning with your fingers,then go the 1/2 turn from there--its nice to be able to slap the valve covers on and have the engine start & run quietly the first shot,and not have to mess with them again,but it doesn't always work out that way,you sometimes have to do it "running" to get the final adjustment right..
 
chulisohombre said:
I’ve always done zero lash with no tapping then 1/2 turn more. I was always told this by engine builder friends and older adults as I was learning.
Click to expand...

Interesting. I suppose the half turn spec was a CYA type deal for gm to make sure lash was tight enough for production maybe?
 
Nope....it centers the cup inside of the lifter
bore... if the cup strikes the clip in the top of the lifter it can knock the clip out and that's no good...( too loose ) the pieces can find their way into the oil pan and be sucked into the oil pump etc..

If the cup bottoms out it can collapse the lifter mechanism that controls the oil flow that acts as the "cushion" part of the lifter that keeps them quiet. ( too tight ) also refered to as a collapsed lifter.

That why I stated above that lifters need
about .020 - .060 of preload. I think
what confuses people is the term zero lash.

zero lash on a NEW lifter is set properly when the rocker nut is tightened just to the point where the slack is removed from the pushrod and rocker and you feel a small amount of drag while spinning the pushrod.

turning the rocker nut an additional 1/4 to 1/2 turn moves the lifter cup down into the lifter body that 20-60 thousandth... of course this all needs to happen with the lifter on the base circle of the cam lobe.

as long as the valve spring tension has been removed from a used lifter long enough to allow the cup to rise up in the body of the lifter, the same procedure applies..

interestingly, one should not place lifters in a pan of oil prior to installing and lashing for the first time...they need to be lubed externally before they are put in the block, and the lash set. Then they will be filled during the prelube sequence. when you see oil coming out of all of the oiling holes on the rocker arms,,you are good to go.
Install the valve covers and crank it up.
 
The oil pre-soak is some old wives tale...origins unknown. The lifters see full oil pressure which is going to do 500% more in seconds than sitting in a pan full of oil overnight. Comp makes a nice tacky cam and lifter lube, essential in the fight against killing cam lobes.
 
wasted wages said:
as long as the valve spring tension has been removed from a used lifter long enough to allow the cup to rise up in the body of the lifter, the same procedure applies..
.
Click to expand...

exactly what i will be dealing with . the rocker arm nuts were all backed off before the engine was stored for a good length of time ( longer than a few months )

i will be rolling the engine to each cylinder to base circle and doing as you said .
 
I've even seen people put the lifters in a pan of oil and then plunge them up and down with a pushrod until they "stack" solid...which is exactly what you don't want.

Oil is not compressible, and when you try to adjust them like this, something has to give,
and what happens is the valve gets pushed open...once the engine starts and the lifters bleed down,all of a sudden all of the lifters are clattering and then they pull the valve covers off and try adjusting them with oil spraying everywhere...
 
sweetk30 said:
exactly what i will be dealing with . the rocker arm nuts were all backed off before the engine was stored for a good length of time ( longer than a few months )

i will be rolling the engine to each cylinder to base circle and doing as you said .
Click to expand...

yup, I read that in your original post....That was a smart thing to do when you stored the engine..most people don't do that. ;) :waytogo:

When I stored my drag car, I used to do that to save the valve springs...with the cam I was running I didn't want the springs compressed on an intake or exhaust stroke for that long... the coils tend to loose tension and you end up with a few weak springs.
 
I soaked new lifters in a coffee can full of new oil while I was taking the engine apart--one of the motor's manuals I had said too,and it also said to "pump them up" with a push rod to ensure some oil got inside the lifter...
Now its taboo to do it this way ?...I see no advantage to install lifters "dry" with only some cam break in lube on its external surfaces,and the instant you crank the engine over,the oil pump pressure is going to pump them up anyways...:dunno:..

Other guys I know just coated the lifters with something like STP and dropped them in "dry" and had no issues,so I guess it doesn't really make much difference..
 
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