Hydraulic Lifter / Pushrod Preload

[Charlie Brown]

Just finished adjusting lifter preload. Engine has sat idle for 5 months. Before doing so, I cranked the engine over to get full oil pressure using only the starter. I adjusted to zero lash plus 1/2 turn on the adjusters. While adjusting, there were a couple of valves that I could not get that 1/2 turn because I started to compress the spring. Could this be that some of the lifters are pumped up more than others? How should I tackle the adjustment on these valves or what am I missing here. Valve train geometry is correct. Shaft setup with Harland Sharp rollers. Approx 4k miles on engine. Engine ran fine before but there was a slight ticking on one or two rockers, thus the reason for adjusting.

 

[BSB67]

How did you adjust to zero? You simply cannot presume cranking over the engine will pump up the lifters. In fact, it’s unlikely.

You need to loosen the adjuster until there is slop. With a very light touch, wiggle the PR up and down while lightly and slowly turning the adjuster until there is no slop. Essentially, sneak-up on zero lash.

If you have factory heads, you can also watch the lifter plunger.

 

[65CopCar]

How did you adjust to zero? You simply cannot presume cranking over the engine will pump up the lifters. In fact, it’s unlikely.

You need to loosen the adjuster until there is slop. With a very light touch, wiggle the PR up and down while lightly and slowly turning the adjuster until there is no slop. Essentially, sneak-up on zero lash.

If you have factory heads, you can also watch the lifter plunger.

I agree. I lightly spin the lifter with one hand and slowly tighten till I feel the least bit resistance then do the 1/2 turn.

 

[BSB67]

Spinning the push rod will not work. There is not enough resistance to spinning.

 

[65CopCar]

Spinning the push rod will not work. There is not enough resistance to spinning.

Oh yeah it does. It does for me at least.

 

[65CopCar]

These guys agree with me.

Adjusting Hydraulic Lifters for Proper Preload - Engine Builder Magazine

In order to adjust the preload the lifter must be properly located on the base circle or “Heel” of the lobe. At this position the valve is closed and there is no lift taking place.You will need to watch the movement of the valves to determine which lifter is properly positioned for adjusting. 1...

www.enginebuildermag.com

 

[dvw]

Spinning the push rod will not work. There is not enough resistance to spinning.

That depends on how good your feel is. I've done it like that for years.
Doug

 

[BSB67]

I’ve spun them too. Now I know better. I adjusted my hydraulic lifters for 0.002 - 0.003” preload. When the only pressure is from the lifter spring on a collapsed lifter the rotational drag on an oiled, broke-in valve train can be undetectable at zero+ preload.

Light upward lift on the rocker works too.

 

[Geoff 2]

The v/spring could start to compress because the lifter has pumped up & is not bleeding down. That does NOT necessarily mean the adjustment is wrong for that lifter. Flat tappet lifters have 0.150" [ or more ] of adjustment range. Anywhere within that range is satisfactory. The reason for such a large adjustment range is production tolerances & future maintenance: head milling, valve jobs etc.
Factory lifters have a failure prone, weak circlip. The reason folks like to set preload tight is because it should limit lifter pump up, but: over revving can punch out the p'rod cup & circlip, maybe bend the prod. Also, trying to set the preload too tight might cause noise because there is clearance now in the valve train when the engine warms up.
So decide on the pre-load. With HS rockers, I would use 1-2 turns on the adj screw.

 

[Charlie Brown]

How did you adjust to zero? You simply cannot presume cranking over the engine will pump up the lifters. In fact, it’s unlikely.

You need to loosen the adjuster until there is slop. With a very light touch, wiggle the PR up and down while lightly and slowly turning the adjuster until there is no slop. Essentially, sneak-up on zero lash.

If you have factory heads, you can also watch the lifter plunger.

This is the method I used. Engine has aluminum heads.

 

[Charlie Brown]

The v/spring could start to compress because the lifter has pumped up & is not bleeding down. That does NOT necessarily mean the adjustment is wrong for that lifter. Flat tappet lifters have 0.150" [ or more ] of adjustment range. Anywhere within that range is satisfactory. The reason for such a large adjustment range is production tolerances & future maintenance: head milling, valve jobs etc.
Factory lifters have a failure prone, weak circlip. The reason folks like to set preload tight is because it should limit lifter pump up, but: over revving can punch out the p'rod cup & circlip, maybe bend the prod. Also, trying to set the preload too tight might cause noise because there is clearance now in the valve train when the engine warms up.
So decide on the pre-load. With HS rockers, I would use 1-2 turns on the adj screw.

Thanks for this. If the lifter is not bleeding down, will it bleed down when running? If not, what are the consequences in regards to setting valve lash. It's a bit confusing for me. I understand the adjustment range built into the lifter, but if I'm unable to get the initial lash correct, how is one able to achive proper specs?

 

[zyzzyx]

Just remember that all of these components expand and contract at different rates. That's why you
preload the lifter somewhere in the middle of that sweet spot. Aluminum heads expand more than
cast iron heads. Pushrods are long and made of steel so they don't grow alot. just follow the printed
instructions.

 

[Geoff 2]

Yes, when running the lifter bleeds it down. Oil is hot, thinner, leakage past the inner piston is easier....& at max valve lift, max spring force is being applied to the lifter piston. If the spring tension is 300 lb at max lift, with 1.5 rockers 450 lb is being applied to the piston.