Hydraulic lifters condition

Wietse

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Hey guys,

As i had rocker shafts removed i decided it was a good idea to redo the hydraulic lifter pre-load after reinstalling the shafts.
I noticed that some of the lifters do not feel quite as solid as the others.
After setting zero lash with the adjustment screw on the rocker i give it a full turn on the screw as pre-load, though most of them are "tight" and actually open the valve, but after a minute or so the valve is closed already and the lifter has bled off, the push rod can then be twisted by 2 fingers. (still can feel resistance, not sloppy or so)
I found a few lifters that will bleed off straight away and therefore do not feel as "tight", the valve does not get off the seat.
Does that mean those lifters are getting worn out and bleed off faster then the others?
Would that give any issues? I guess that during engine operation they are always full of oil and pressurized and do their job as any other lifter.
Just wondering if it is time for a new set of lifters now.
Oil pressure is 50-60 psi with 20W50 oil, 440 HP engine.

Anyone has some thoughts about this?
 

steve340

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If the engine is not noisy and runs OK I would forget about it.
A new set of lifters are probably going to be worse.
 

Wietse

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Thx guys.
These lifters must be old types, my guess is it must have been rebuild 15-20 years ago but has not done too many miles since.
Probably the type of quality you may not find anymore.
They do make a slight ticking noise, nothing too concerning i believe.
You can hear it when you pop the hood but otherwise you can not hear them.
I do think that on cyl #5 or 7 there is 1 that makes more noise during driving as i can hear the ticking coming from the foot well.
It sounds like an exhaust leak but i checked and did not find any leaks on the header flange.
 

steve340

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A hydraulic lifter that leaks down can be stripped and checked/cleaned out if you can be bothered doing the work.
They have a little check valve in them that can sometimes not seat correctly or get stuck with debris. It is probably worth a try if you only have 2 or 3 problem ones.
There are no guarantees you will fix it.
So few engines have a flat tappet hydraulic in them these days it does seem the manufacturing process for them now is questionable.
I will not fit a hydraulic flat tappet lifter any more. I would rather set valve lash.
A noisy hydraulic lifter drives me nuts.
 

Cranky

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Some lifters will bleed down faster than others is why you might be finding mushy ones. In most cases factory style lifters are supposed to be adjusted with .050/.060 preload but I usually go half of that. Got to know what the thread pitch is of your adjuster screw is to figure how much it moves per thread. Many are 24 tpi and some are 20 tpi. If they are 3/8" in diameter, they are 24 and 7/16" diameter is 20.....most likely.
 

Wietse

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I would take the time and service them if it knew i would solve the issue, since i have quite low manifold vacuum i was considering buying a set of Rhoads variable lifters to gain some vacuum at idle, as far as i know they are still making reliable hydraulic lifters of good quality.

The adjusters are 3/8"-24 thread indeed, i believe a full turn is .040" pre-load.
This is what i set last time and have been running well since then so i set them back to that.
My cam is from Hughes Engines, so my guess is the lifters are as well, they recommend .080" pre-load but i don't know why they recommend so much.
 

steve340

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Broad brush strokes a Rhoads lifter is very "loose" tolerance wise and has a lot of leak down. Most likely the engine will loose torque and the noise may drive you nuts.
The reason Hughes recommends so much preload is to minimise the oil space left in the lifter after adjustment.
I would try that it will cost you nothing to go with Hughes recommendation.
It does work I do it a slightly different way but you can gain 500 - 1000 rpm more out of the engine.
 

Cranky

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Broad brush strokes a Rhoads lifter is very "loose" tolerance wise and has a lot of leak down. Most likely the engine will loose torque and the noise may drive you nuts.
The reason Hughes recommends so much preload is to minimise the oil space left in the lifter after adjustment.
I would try that it will cost you nothing to go with Hughes recommendation.
It does work I do it a slightly different way but you can gain 500 - 1000 rpm more out of the engine.
Years ago, if the lifters were the anti-pump up, yeah. Don't even know what is used these days but used to gain rpm by setting a hydraulic lifter with less preload that way they can't pump up because they are already up. One thing that needs to be checked when doing that is what kind of keeper is in the top of the lifter.....the 'paper clip' style or an actual snap ring. The snap ring style keeper is better for doing the shallow adjustment.
 

steve340

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If you "bottom" the lifter out it tends to work more like a solid lifter.
You have to watch you do not stop the lifters pushrod oiling though.
I stopped mucking with them just go straight to a solid.
 

Cranky

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If you "bottom" the lifter out it tends to work more like a solid lifter.
You have to watch you do not stop the lifters pushrod oiling though.
I stopped mucking with them just go straight to a solid.
That's way you don't let them go all the way up but the snap ring style are better at holding things together if one does pump up more. That was one of the tricks I did on my first engine 50 years ago and it did well and many others after and then not too long ago, David Friburger brought it up. That kind of surprised me that it's still being done.....well, maybe only by him and me lol. Thing is, I'm not going with a solid lifter on a mild cam but these days, I'm not doing much anyways. :(
 

Wietse

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The Rhoads lifters supposed to leak off fast at low rpm, this is what results in a short valve duration which makes it idle a bit better with big cams.
My cam is not that big, but for some reason the vacuum is low and i was hoping to gain something there if i would go for these Rhoads lifters.
Then again, i fear for replacing lifters due to issues and run the cam to the ground.
Anyhow, guess i will leave them for now and drive it as long as the weather permits, when the shitty weather comes back in i can have a go at these lifters.
My lifters are with the proper snap rings so i guess these are old-style solid build lifters.
 

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