TheSamba.com :: View topic - Hydraulic lifter preload (bled vs not bled)

Fri May 06, 2022 4:31 pm

When adjusting preload...
Should the lifters be bled of air... Or should they be bled of oil instead?

I'm thinking that if the lifter is solid from being filled with oil then it won't be possible to adjust the preload. The 1.5 turns of the adjuster will then just open the valve.

If, on the other hand, there is no oil inside the lifter the 1.5 turns will push the lifter cup down the bore, which is what we want.

While writing this I get a feeling that it doesn't matter but I'd like to know from you experienced folks...

Fri May 06, 2022 4:40 pm

The lifters should be bled of air and filled with oil.

Turn the adjustment screw slowly after it makes contact with the valve stem and oil will be forced out of the lifter. But even if you don't the lifter will adjust itself when the engine is started.

It's also much easier to feel when the adjustment screw contacts the valve stem because of the hard, oil-filled lifter.

If there is air in the lifter, it will clatter like crazy for 15 minutes of driving until it bleeds itself.

Fri May 06, 2022 5:47 pm

Read: https://web.archive.org/web/20090720020352/http://www.bostonengine.com/articles/hydraulicll.htm

also:

Sat May 07, 2022 2:04 pm

After pre load is set... if I then want to proceed to check pushrod length and geometry with the oil filled lifters... will they be oil filled long enough for that to be possible?

Sat May 07, 2022 2:44 pm

I don't due hydraulic lifters in my VW engines. Can't answer that. I would think you would set the preload on one and then inspect the geometry. If it isn't right you would adjust the pushrod then do it again until you got it right, then make 8 pushrods that length.

Sun May 08, 2022 2:04 pm

VWLover77 wrote: The lifters should be bled of air and filled with oil.

Turn the adjustment screw slowly after it makes contact with the valve stem and oil will be forced out of the lifter. But even if you don't the lifter will adjust itself when the engine is started.

It's also much easier to feel when the adjustment screw contacts the valve stem because of the hard, oil-filled lifter.

If there is air in the lifter, it will clatter like crazy for 15 minutes of driving until it bleeds itself.

Alright, so what you are saying is that the valve spring is less strong/collapsible then the lifter even when the lifter is filled with oil?

Shouldn't the lifter act as a solid lifter when it is filled with oil? If the oil can be forced out of the lifter by the force of the valve spring how can it function as solid lifter capable of lifting the valve?

Is it because there isn't any oil pressure from the engine running?
Is it the oil pressure that makes the lifter in-compressible?

Or is the lifter only in-compressible when moving in one direction, being pushed from the cam?
(because of the ball valve inside shutting off the oil pathway when the lifter moves outward, away from the cam)

Sorry for the stupid questions, just trying to understand how this works...

Sun May 08, 2022 3:22 pm

regardless of the amount of oil in the lifter the small spring always pushes it to full extension if it is working right. Once pressure is put on the lifter it will lose oil at a set rate depending on the oil viscosity and temperature. The second you pre-load it, it will start bleeding down.

Sun May 08, 2022 4:12 pm

Some people have suggested that making a dummy solid lifter out of an old hydro one is the only way to check geometry for us hydro guys...

In this post, tencentlife describes one way how to make a dummy lifter https://www.thesamba.com/vw/forum/viewtopic.php?p=6746380#6746380

I followed the steps and now have a dummy lifter with about ~1mm preload

I measured the lifter fully extended with an M10 nut on top. I got 51.44 mm.

When the lifter is preloaded with 1.5 turns, the cup should be 1.14 mm lower 51.44 - 1.14 = 50.30 mm

(1.5 turns on the adjustiment screw equals 1.14 mm preload on the lifter side of the stock 1.3:1 rocker... this I got from Ratwell...
0.5 turns is 0.38 mm movement of the piston inside so 1.5 turns is 1.14 mm)
https://www.ratwell.com/technical/HydraulicLifters.html

Then I removed the plunger, spring and cup. Then found a M10 bolt+nut of proper length, threw them (screwed together) inside the lifter. Adjusted the nut until the height was right. Put the pushrod cup on top. Measured with an M10 nut on top of the pushrod cup. After a few tries and adjustments of the nut/bolt inside the lifter I got 50.30 mm.

So this should simulate a hydraulic lifter preloaded with 1.5 turns in a running engine.

Sun May 08, 2022 4:16 pm

until you get a lifter set that has been resurfaced and is a different length.

Mon May 09, 2022 12:13 am

Lifters don't necessarily leak down very fast if at all. A couple of years ago I let my 2.1L WBX Vanagon engine sit for well over a year and it was nice and quiet when I fired it back up as the lifters had not bled down. Firing up a cold engine (especially one filled with a thicker oil grade) and then shutting it off before it warms is the way to get lifters to leak down.

You can adjust your lifters accurately whether they are full of oil, empty of oil, or anything in between, what you need to do is find the point of contact which can be very subtle, and may not feel the same if you repeat the process multiple times. Yes if a lifter is all the way pumped up, it will open the valve as you set the preload. In the extreme if all the lifters are fully pumped up you might not be able to get the engine to start and run. One way to go is to set one side at 0.006" lash and then adjust the other side to your chosen preload. This way the engine should start well enough and then once it has been run long enough for the preloaded side to self adjust you can go back and adjust the unpreloaded side.

Mon May 09, 2022 5:55 pm

Wildthings wrote: Lifters don't necessarily leak down very fast if at all. A couple of years ago I let my 2.1L WBX Vanagon engine sit for well over a year and it was nice and quiet when I fired it back up as the lifters had not bled down. Firing up a cold engine (especially one filled with a thicker oil grade) and then shutting it off before it warms is the way to get lifters to leak down.

You can adjust your lifters accurately whether they are full of oil, empty of oil, or anything in between, what you need to do is find the point of contact which can be very subtle, and may not feel the same if you repeat the process multiple times. Yes if a lifter is all the way pumped up, it will open the valve as you set the preload. In the extreme if all the lifters are fully pumped up you might not be able to get the engine to start and run. One way to go is to set one side at 0.006" lash and then adjust the other side to your chosen preload. This way the engine should start well enough and then once it has been run long enough for the preloaded side to self adjust you can go back and adjust the unpreloaded side.

Ok, thanks for the info! Good to know that adjustment can be done no matter what state the lifter is in.

I tested screwing the adjuster with a -new from the box- hydraulic lifter. Before inserting I tested pushing the cup with my thumb... almost no give, very stiff.

After inserting the lifter, no matter how much I screwed the adjuster I could not get the valve to open... so the strength of the valve spring is probably pushing out the oil from the lifter.

After removing the lifter the cup had a lot more travel when testing with my thumb again, confirming that oil had seeped out of the lifter.

Then I tested with the dummy solid lifter I made from an old hydraulic as described in post above...

I found there are four steps while screwing the adjuster in.

1. Gap
2. Point of contact
3. Rocker arm flexes/moves opposite direction, away from valve tip. This movement is quite subtle and only lasts during less then a quarter of a turn.
4. Rocker arm moves towards the valve tip and begins to compress spring.

I was surprised that number 3 happens. I'm guessing will happen with the hydraulic lifter too when the engine is running.

I'm still not sure how to check if my stock pushrod length of 261mm is still OK?

Would this be a way to do it...?

1. Insert hydraulic lifter and set preload to 2 turns.

2. Insert dummy lifter and see if there is any gap while keeping the adjuster at the same position as had from point 1.

Mike, do you use a dummy solid lifter when you check pushrod length on a hydraulic engine?

Does even pushrod length matter that much when we are using hydraulic lifters?
Won't the lifter compensate anyway?

Mon May 09, 2022 6:17 pm

I am not sure what you mean by the lifter flexing away from the valve tip. When attempting to find the point of zero lash you do not load the lifter by pressing on the rocker arm.

Tue May 10, 2022 7:40 am

Wildthings wrote: The lifter doesn't have much compensation, maybe 0.040" (1mm) so can't make up for a pushrod that is the wrong length.

I was told that if I change deck height, then I would have to adjust pushrod length and geometry would change. My thought here was that if the deck change is small...

Say I lower the deck height by 0.5 mm (from 1.52 mm to 1.02 mm)
and fly-cut the heads 0.2 mm that would be below the 0.040" (1 mm) you mention. Total shortening = 0.7 mm

If we count the 0.006" (0.15 mm) that the valve train expands with heat then that would be even less of a change.

So couldn't the lifters allow the 0.7 mm shortening by pumping up a little more?

Meaning that I do not have to change pushrod length or geometry for such a small change.

Perhaps I am missing something?

Wildthings wrote: I am not sure what you mean by the lifter flexing away from the valve tip.

Not the lifter flexing away, perhaps I was not clear... the rocker arm flexes back before overcoming the force of the valve spring, then it moves forward opening the valve... This is clearly visible to me while adjusting the screw with a solid dummy lifter installed.

This surprised me because I had thought the adjuster would be able to open the valve DIRECTLY after point of contact. Instead, as the adjuster screw continues past the first point of contact, it pushes the rocker back for about a quarter of a turn. THEN the lift starts.

My guess is that this will also be happening when the hydraulic lifter is installed and the engine is running, because the hydraulic becomes solid when pumped up.

Wildthings wrote: When attempting to find the point of zero lash you do not load the lifter by pressing on the rocker arm.

I do not load the lifter... but I gently back the rocker off from the valve tip without putting pressure on the lifter... just so that the gap appears at the valve tip instead of between the rocker and pushrod.

Tue May 10, 2022 11:45 am

You didn't make up for any of the machining by adding cylinder base shims? If you used stock height pistons and cylinders, then if you have shimmed the barrels so your deck height is within the normal range you should have enough adjustment in the valve train.

Tue May 10, 2022 2:42 pm

Wildthings wrote: You didn't make up for any of the machining by adding cylinder base shims?

I'll give you the whole story...

My first plan was to keep the engine as stock as is could be. So essentially keeping the stock setup that was handed to me by the previous owner. This strategy was mostly to save time and money and not complicate things when this was my first build.

So I replaced the 0.2 mm shim and the 0.8 mm gasket with a 1 mm shim... ...keeping the previous owners deck height of 1.52 mm
I was told that the fly-cut of 0.2 mm would not effect geometry, because of this I did not add that number when calculating the shim. I also learned from you Wildthings that I shouldn't go over 1.5 mm in deck and preferably go under 1 mm. If I would have added the 0.2 mm flycut to the shim, I would have to go to the next shim size ,and then I would arrive at 1.77 mm deck... which is above the maximum 1.5 mm deck as recommended by you.

I then toyed with the idea that I should follow your advice and try to go closer to 1 mm deck, thereby abandoning the idea of having everything stock. I ordered another set of shims from my VW-dealer, this time 0.5 mm. So then I would arrive at 1.02 mm deck.

I was ready to go for this but then I was told by someone at the forum that, lowering the deck would mean I have to do the geometry and pushrod length... Since this seemed too complicated for me I decided to just stick with the 1.52 mm deck height handed down to me by the PO.

But then I got paranoid...

What if the geometry set by my previous owner was not correct?
Perhaps the cylinder sealing surfaces had been machined?

I hadn't thought about that possibility.

Words from SGKent, Jake Raby and Raygreenwood about always checking and being thorough, and not trusting math only measurements, was echoing in my brain.

Especially after reading a thread started by SGKent where he mentions two different type 4 engine blocks having both having a naked deck height of 0.74 mm. If 0.74 is the stock naked deck height....comparing this to my naked deck height of 0.52mm I was wondering if my case had been machined.

https://www.thesamba.com/vw/forum/viewtopic.php?p=9442549

So then I decided I should order an adjustable pushrod and try to do the geometry even if I was aiming for stock, just to be on the safe side. Also since my old pushrods were a bit bent I was going to do cut the new pushrods to length anyway.

But then I read that you can't do the geometry and pushrod length with hydraulic lifters because the oil just leaks out under pressure making the lifter shorter and shorter and giving me a false reading on the pushrod length...

After trying to understand this pushrod length and geometry for a while, creating a dummy lifter and experimenting, I still feel like I don't have a clue...

So that's why I asked how much the hydro lifters can compensate the valve train geometry. If they can then it would save me a lot of time and effort trying to understand this geometry thing...

Wildthings wrote: If you used stock height pistons and cylinders, then if you have shimmed the barrels so your deck height is within the normal range you should have enough adjustment in the valve train.

And what is considered normal range?

Tue May 10, 2022 3:56 pm

I would have assembled the cylinders and heads on one side, put the lifters in, then existing pushrods, and rocker arms etc.,, Then I would have adjusted the lifters for proper pre-load and looked at what the geometry was on the valve that was at on the base circle. If it looked like the lifter screw was in a good place I would have stopped there. Or if I wanted to be anal, I would have gotten a solid lifter, compared it's length to a stock Hydraulic lifter, dropped it in, and measured that way, then pulled it out and replaced it.

Tue May 10, 2022 7:56 pm

A half a millimeter isn't going to make much difference in the geometry. That is about 2/3 turn of the adjusting screw, and would represent about 6% of the valve lift assuming a 0.4" lift.

I was wrong to say you have to worry about the adjusting ability of the lifter. It actually doesn't enter in here as it would on say an old Ford VW where instead of having adjusting screws you buy different length pushrods to do the rough valve adjustment and let the lifters do the rest.

Wed May 11, 2022 6:02 pm

Wildthings wrote: A half a millimeter isn't going to make much difference in the geometry. That is about 2/3 turn of the adjusting screw, and would represent about 6% of the valve lift assuming a 0.4" lift.

I was wrong to say you have to worry about the adjusting ability of the lifter. It actually doesn't enter in here as it would on say an old Ford VW where instead of having adjusting screws you buy different length pushrods to do the rough valve adjustment and let the lifters do the rest.

So if I lowered deck height by 0.5 mm and had a flycut of 0.2 mm, that would still not affect geometry enough that it mattered? ...So I could keep the stock pushrod length of 261 mm even though the heads are a total of 0.7 mm closer to the pushrods?

If the heads are lowered 0.7 mm... and you DON'T shorten the pushrods 0.7 mm.... Does the adjuster screw take care of the extra 0.7 mm when you are finding zero lash? OR ....Is the lifter preloaded an extra 0.7 mm because the pushrod gets pushed further down by lowering the head?

Could you say that lowering the deck height 0.5 mm and flycutting 0.2 mm is the same as lengthening the pushrod 0.7 mm? I mean in effect, the pushrod is of course the same size...

SGKent wrote: I would have assembled the cylinders and heads on one side, put the lifters in, then existing pushrods, and rocker arms etc.,, Then I would have adjusted the lifters for proper pre-load and looked at what the geometry was on the valve that was at on the base circle. If it looked like the lifter screw was in a good place I would have stopped there. Or if I wanted to be anal, I would have gotten a solid lifter, compared it's length to a stock Hydraulic lifter, dropped it in, and measured that way, then pulled it out and replaced it.

Then what does it look like when the lifter screw is in a good place? Because I know that the screw should be parallel at half lift. On base circle the valve is closed so the screw is not parallel, right?

Sat May 14, 2022 4:14 pm

Here's what I've done so far...

Made two dummy solid lifters with 1.14 mm "preload"
I set the cup between 1.10 and 1.20 mm lower then a new lifter with zero pre-load.
Reason for 1.14 mm is because that is how much 1.5 turns on the adjuster screw should pre-load a hydraulic lifter.
I used these "pre-loaded" solid dummy lifters for all measurements instead of hydraulic lifters, because I didn't want them to bleed oil under pressure.

Measured the lift on intake #4 w. dial indicator:

First a pic of my setup:

1st measurement
Full lift 8.24 mm = 0.324"
Half lift 4.12 mm = 0.162"

2nd measurement
Full lift 8.30 mm = 0.327"
Half lift 4.15 mm = 0.163"

(Reference "cam card" lift for stock cam w. stock rockers: 8.36 mm = 0.329")

Tracked the adjuster swipe on the valve tips for #4 intake + exhauset

Adjuster trace... used a black permanent marker as dye

Eyeballed the adjuster to tip angles at zero lift, half lift and full lift

Zero lift

Half lift

Full lift

What do you guys think of the results?
Adjuster traces?
Adjuster to tip angles?

Thank you for your help!

Sat May 14, 2022 4:45 pm

Swipe looks good, half lift looks not square.