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Hydraulic roller lifter failure

Hydraulic roller lifter failure

Hydraulic roller lifter failure

(OP)
I'm having what I believe are premature roller failures. I'm seeing failures at between 2000 hrs and 10,000 hrs. I realize this is between 120,000 miles and 600,000 miles. These are in ford big block engines used in stationary continous duty applications. They are ran at 1800 rpm with oil being changed every 500 hrs. It is a mineral oil.

It is a retrofit roller lifter and cam. The cam has about .300 lobe lift and 195degrees at .050 duration. The springs are 110# seat pressure with a rating of 231#.

After through disassembly of several failed lifters and cams. It appears the needle bearings are microwelding to the axle assembly.

I have submitted cams and lifters to the manufacturer and he has said they are just wearing out. My belief is the spring pressure is to light and the lifter is bouncing coming off the nose.

Any other thoughts would be greatly appreciated.

RE: Hydraulic roller lifter failure

in my small block chev continuous run applications i switched back to old school lifters and cams and had better longevity by  alot. as long as proper lube and break in was done at start up. standard lifters and came out lasted almost 2 to 1

RE: Hydraulic roller lifter failure

(OP)
Are using non-ZDDP type oil?

RE: Hydraulic roller lifter failure

Sounds like a lube failure, but why run such high springs pressure at 1800 rpm?

"You see, wire telegraph is like a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? Radio operates the same way: You send signals here, they receive them there. The only difference is there is no cat." A. Einstein  

RE: Hydraulic roller lifter failure

The clue of micro welding suggests lack of lube. The axle of the roller relies on splash oiling thrown off the crankshaft. Some oil will migrate down from the clearance between lifter and bore, but there may not be enough that makes it to the axle. The aftermarket cam co. Iskedendrian has a roller lifter that replaces needle style with a bushing. Greater load capability but still would require continuous oil supply. Are the lifters that failed always in the same position or do all of them show signs of distress?-----Phil

RE: Hydraulic roller lifter failure

I agree re the lube. 1800rpm is not a lot to throw oil at the cam. I normally break in cam/follower combos at 3000rpm just to ensure lubrication.

Maybe some sort of oil squirter via a notch or hole in the big end of the rod.

Regards
Pat
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RE: Hydraulic roller lifter failure

(OP)
I'm not discounting lube. I am surprised there wouldn't be enough splash considering. In an on-highway application the normal operating RPM is 1800 to 2000 RPM.

The spring pressure was what the cam manufacturer specified with cam lift and duration.

It is currently built with the largest capacity pump available.

From the samples I've looked at it appears the center 2 cylinders consistantly have the greatest failure rate but, it is random between intake and exhaust lifters.

I'm considering angle drilling holes (.100) from the lifter valley to as close to the roller end as possible.

Thanks everyone for the input

RE: Hydraulic roller lifter failure

Have you done oil analysis? Have you considered a quality full synthetic? 500hrs seems like a lot of hours between changes for a mineral oil. It might even be too much for a synthetic.

I would also suspect the lifter itself. It seems there are a few models of lifters that are considered much more reliable if you hang around performance forums enough.

The spring pressure comments are probably correct too. It sounds like that's the recommended spring for the cam, which is likely capable of controlling the valves up to something like 5500rpm or 6000rpm.

You could try cutting holes in the valve covers and record the pushrod/rocker/valve moving with a high speed camera. That might show if you have some strange valvetrain harmonic happening.

 

RE: Hydraulic roller lifter failure

Roller followers tend to break more from valve train separation than from valve spring pressure, however 1800rpm and a cam designed to be efficient at that speed would require minimal valve spring pressure.

Certainly a worn cam lobe can lead to erratic follower motion and valve train separation, so maybe that was where the problem started.

I agree, without knowing a few pertinent details, that 500 hours seems like a long oil change interval.

Regards
Pat
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RE: Hydraulic roller lifter failure

got any pictures of the micro welding?
How about the condition of the rollers, axles and races of some 5000>10000 hr lifters that have not failed?

If you can provide the dimensions of the rollers and races it might be interesting to see if the operating temp oil satisfies the "kappa" requirements traditionally described as necessary to achieve elasto-hydrodynamic lubrication in rolling contact bearings.

RE: Hydraulic roller lifter failure

(OP)
On the oil change interval. These engines are started and ran until it's time for preventive maintenance. So there is very little cold start time for acids to buildup in the crankcase. They also have a 5 gallon reserve that is constantly topping off the crankcase. So, in 500 hours it may receive as much as 10 quarts of replacement oil prior to the oil change.

Right now I'm wainting to hear back from a different cam company for there opinion of the failure mode. When I get an answer I'll post it.

Thanks for all of comments

RE: Hydraulic roller lifter failure

Oil?  Brand, viscosity? Additives?
Old aircraft engines, diesel engines of the past all used roller cam an tappets, and seemed to live just fine, as do lots of modern automotive engines nowadays. Need to answer questions above and pictures of needles and contact surfaces. If water is the lubricant used then that is the problem. Too much info missing here.   

RE: Hydraulic roller lifter failure

(OP)
I just wanted to follow up. I still haven't received any info from the cam manufacturer. I did do considerably more research and I believe valve recession is having an impact. As the valves are receding it's increasing the valve spring installed height. I believe it's reducing valvetrain control allowing the lifter to slide and bounce on the lobe.

RE: Hydraulic roller lifter failure

Sounds like a logical conclusion. Install hardend seats?------Phil

RE: Hydraulic roller lifter failure

(OP)
They have hardened seats and inconel valves. I suspect the seat width is too narrow and not having enough cooling effect on the valve. From the info I can gather the seat width is between .040 and .060 on both intake and exhaust.

RE: Hydraulic roller lifter failure

Can you set up an oil drip feed into the manifold to feed two stroke oil or upper cylinder lube.

Regards
Pat
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RE: Hydraulic roller lifter failure

(OP)
I can't introduce anything in the the intake tract because of emissions.

RE: Hydraulic roller lifter failure

What is the fuel? Do the valves have rotators? I'm second hand aware of some applications that developed seat recession when using positive valve rotation.

RE: Hydraulic roller lifter failure

(OP)
The fuel is Natural Gas and the valves do not have rotators

RE: Hydraulic roller lifter failure

Oil filtration? I'd agree with the poster that suggested an oil analysis. 500 hours does seem like a lot of hours on a change, even considering there is minimal cold startup.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

RE: Hydraulic roller lifter failure

Are there engines run at high load continuously. On a road application, the throttle opening changes regularly so there is often periods of overrun against a closed throttle thereby pulling a vacuum in the manifold and ports which will likely pull some oil past the valve stem seals and the PCV. If it very rarely runs at high manifold vacuum, could you leave the valve stem seals off as a back door way to introduce a bit of oil to the seats.

I also agree the seats are narrow for an endurance engine.

I wonder how much worse if any the seat recession would be with springs hard enough to still retain full valve train control after the seats had receded? ie just install shims to reduce installed height by a bit more than the expected seat recession.

Regards
Pat
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RE: Hydraulic roller lifter failure

Valvetrain control problems at 1,800 RPM? Sounds crazy...

RE: Hydraulic roller lifter failure

Are the seats eroding at the surface where they contact the valves or are they sinking into the castings or both. I have seen seats sink into castings on aluminium heads and I have seen the head deform over time if the area was thin between the port roof and the spring seat. These happened reasonably quickly, but they also had 400# on the seat. I doubt yours are over 150# on the seat and I think you probably have iron heads. Also the ones I saw where the port roof sank, the aluminium heads had been welded and we think that tempered and softened the material.

If you are running aluminium heads, have they ever been overheated or run hot enough long enough to anneal or soften the material.

Regards
Pat
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RE: Hydraulic roller lifter failure

Its time to try a quality brand of synthetic oil. So what viscosity is the oil?

RE: Hydraulic roller lifter failure

(OP)
Pat
The recession only appears where the valve contact area is. There is no sinking into the head. These engines are always ran at high load/low manifold vacuum. I'm trying to gather enough data to suggest starting with a tighter installed height.

Dicer
There is a lot of superstition about oil not mixing with natural gas. It's a very big struggle to get TPTB to allow a change in viscosity or type. Currently, there using straight 30W.

Thanks

RE: Hydraulic roller lifter failure

Have you calculated/measured how much seat pressure you lose from the valve recession? I'd be amazed if that's the reason, unless the valve train is very heavy.

"You see, wire telegraph is like a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? Radio operates the same way: You send signals here, they receive them there. The only difference is there is no cat." A. Einstein

RE: Hydraulic roller lifter failure

The next question is who's the manufacture of the lifters? And have you tried someone else for lifters? It looks like there is no mention of the type of lifter meaning is it solid or hydraulic?

RE: Hydraulic roller lifter failure

I've done a fair amount of engines dedicated to using propane and CNG fuel. Most of them use sodium filed exhaust valves. Also I've seen exhaust springs that lost most of their pressure due to overheating. Overheating was due to diminished splash oil supply to provide cooling. Those springs also had a lot of coking attached to them. Does the engine in question show any indication of those conditions?------Phil

RE: Hydraulic roller lifter failure

Good points smokey.
A significantly wider exhaust valve seat should also help reduce exhaust valve temperature.

Regards
Pat
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RE: Hydraulic roller lifter failure

(OP)
Dicer
After speaking to a number of valve train manufacurers there are only one or two retrofit hydraulic lifter manufacturers in the country. I have sent samples to several valvetrain companies for their opinions. These are retrofit style hydraulic roller lifters.

Smokey
The field samples I've seen are very clean around the spring area. The only wear I've seen is the normal ash around the valves and very clear valve and seat wear marks. Also, of the data I've been looking at there is no clear prevelence of either intake or exhaust valve receding more then the other.

I did get a preliminary report from one of the cam guy's. "The loadings you are using do not coincide with the wear on nose of cam lobe." "Lubrication seems to be OK as there is no discoloration at roller wheel or cam lobe." He said he had some other things to evaluate

RE: Hydraulic roller lifter failure

"The loadings you are using do not coincide with the wear on nose of cam lobe."

A bit vague, no?
I will guess he's saying the cam wear exceeds what he'd expect at those spring loads & hours of operation?

May I ask what the part# on the heads is?

Did you switch to a roller cam to try and increase cam/lifter life? or?

Forgive me if you've answered this one already, but,
Have you tested & compared the springs @ the affected lifters vs the others?
Is the valve recession associated with the abnormal lifter wear or is that consistent?

RE: Hydraulic roller lifter failure

I find it hard to believe valve seats eroding would cause such a reduction in spring pressure that you'd have issues. Have you done any measurements? You can get an on-head spring pressure tester for around $250 from Summit or Jegs if you're in the US and verify what spring pressure you have as installed.

A long standing trick to get more oil to the cam/lifter interface area is to groove the lifter bores. I'm not sure that would help with oiling the roller bearings though.

What does the cam profile look like? I doubt you're running a cam with agressive ramp rates, but that is still something to investigate.

RE: Hydraulic roller lifter failure

At 1800 RPM the cam ramps would have to resemble square waves! The OP can rule out high inertial effects and combustion pressure loading. That leaves excessive valve spring pressure, lube or material problems.

"You see, wire telegraph is like a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? Radio operates the same way: You send signals here, they receive them there. The only difference is there is no cat." A. Einstein

RE: Hydraulic roller lifter failure

(OP)
FoMoCoMoFo
We use D9 heads 50% we have cast ourself and the balance are reclaimed. Because of the removal of ZDDP from oil. We started to have what appeared to be a large failure rate of flat tappt cams(This was prior to my employment here) We are doing a trial with a couple of different brands of lifter but it's to early to tell whether they are working. Also I believe the lot sample is too small (2 units)for an effective test. From the data I've extracted there seem to be a correlation between valve recession and lobe failure.

Lionel
We have seen between .050 and .100 valve recession. With our spring rates .050 works out to be 15% spring pressure loss on the seat.

Lionel,Metalguy
I thing the rates are pretty aggressive because of the low RPM usage. I do have some concern about the backside of lobe being too aggressive. I have suggested smoothing out the slope a little TPTB were not very receptive to the idea of a cam change.

RE: Hydraulic roller lifter failure

Well, it's sounds to me like you've got a cam that sounds mild by the numbers, but is actually a bit too "radical" for the sort of longevity you want.
And It's just beating up the valves/seats & lifters.
Still..
If I were the lifter manufacturer I would probably work on some positive oiling method.
Knowing that engine pump combo, I bet they're surrounded by 50+ PSI oil..
It also sounds as though the cam is just borderline and could be made to work with just a little gentler ramps. especially on the closing side..

RE: Hydraulic roller lifter failure

I can't remember reading it. Are the lifters solid or hydraulic. A solid lifter on a hydraulic cam will beat the valve train to death.

Regards
Pat
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RE: Hydraulic roller lifter failure

Some more questions & comments:

Did you see a substantial performance gain with this cam switch?
Is max performance/efficiency even an issue?

I had a similar problem years ago. I was seeking maximum reliability & durability in that same engine
and so was wanting to use a mechanical
(not hydraulic) cam. I could not find one with as short a duration as yours. And the ones that came close still required fairly outrageous spring pressures.
I think the cam makers figure if you're using a roller or solid lifter you want to take full advantage by using an aggressive profile with a rapid open close rate, and therefor require appropriate springs.

I spoke with the tech guy at one famous company whose high torque grind required springs rated in their literature to 7500+ RPM
When asked if I could go lighter on the springs if I swore to limit RPM to say 4000?
The answer was, absolutely not!

I'm not a fan of synthetic oil and very long change intervals. but, if ever there was an application for these, yours is it!








RE: Hydraulic roller lifter failure

Retrofit lifters? Wear on cam? Isn't the cam nose wear the result of the needle bearings locking up and the roller doing the same? Or is it a tracking problem, meaning the rollers are cocked and axis not parallel with cam axis.

RE: Hydraulic roller lifter failure

for natural gas compression running continous in the 1800 rpm range using standard flat tappets with hardened valves and seats running 15w40 or straight 40w oil we are getting 3 to 4 yrs run time on heads,cams, etc.

RE: Hydraulic roller lifter failure

>"I spoke with the tech guy at one famous company whose high torque grind required springs rated in their literature to 7500+ RPM
When asked if I could go lighter on the springs if I swore to limit RPM to say 4000?
The answer was, absolutely not!"<

Be real interesting to know the why of that statement.

"You see, wire telegraph is like a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? Radio operates the same way: You send signals here, they receive them there. The only difference is there is no cat." A. Einstein

RE: Hydraulic roller lifter failure

(OP)
Thanks for all of the responses. I'll try to answer all of the questions.

FoMoCoMoFo
Oil pressure does stay 50psi+. We are working on a spray bar or something like that to spray the rollers. I was not involved in the cam selection process. What I have found interesting is the overall HP of the engine needs to be limited to stay in a certain EPA engine range. Yet, they shortened the duration and increased lift over stock.

Dicer
I'm unclear of exactly what the root cause is. One cam manufacturer said the engine needs more spring pressure to ensure the roller is rolling on the base circle. They believe the roller is skidding and flat spotting. Another manufacturer said there is too much spring pressure and its causing wear on the roller axle. I'm not sure on misalignment. These lifters are tied together with a tie bar. I would expect both lifters to have the same wear pattern if there was a misalignment. This hasn't been happening in the majority of the cases.

Pat
These are hydraulic lifters on a hydraulic cam.

BCS5274
I have seen the same thing as you in the past. Thats one of the reasons I'm looking hard at valve seat width. Are the engines you deal with Automotive Derivatives? What type of head life are you seeing?

RE: Hydraulic roller lifter failure

Yes. I saw the heading after I posted.

The shorter duration with higher lift is normally done to make more power at lower rpm.

My next move would be wider seats and if possible, reduced valvetrain weight.

Also check alignment of lifter bores to cam and if cam walk is restrained sufficiently to keep the rollers in full contact across the full width of the roller.

The oil spray bar can't hurt. An oil formulation with good anti wear additive can't hurt. I presume the cams are steel and properly hardened.

Also I believe that Iskenderian now makes a roller follower with a plain bushing rather than needle rollers. These carry higher shock loads without damage but need more lube.

Regards
Pat
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RE: Hydraulic roller lifter failure

As to the why of that statement.

I'm guessing the cam maker would rather you wear things out from excess pressure than destroy them more catastrophically from too little..

This was 25+ years ago and I don't recall the details of the conversation. He correctly pointed out that his people were better equipped to study valve train dynamics than I was.
But, he also seemed to imply that the relationship between spring pressure requirements & RPM was not as simple, direct and linear as a simpleton such as myself might think it is.
Was he right?
I ramble on here only because it may relate to the OP.
Whoever DID select the cam may well have chosen the most suitable roller cam available.
And yet, It may be too "radical" for longevity.
And maybe the cam maker is, for whatever reason, hesitant to adjust the spring pressure requirement down in line with the low 1800 RPM
speed ?

I guess if the TPTB like the cam, they can deal with making it and everything else survive?




RE: Hydraulic roller lifter failure

Some cam grinders strongly urge users to run light pressure springs for the breakin of flat tappet cams, then change them to allow high RPM operation.

"You see, wire telegraph is like a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? Radio operates the same way: You send signals here, they receive them there. The only difference is there is no cat." A. Einstein

RE: Hydraulic roller lifter failure

fmangas;
yes we are running 5.7l gm industrials and some 7.4l gm

in the 1500 to 1800 rpm range our engines run continous for 3 to 4 years depending on fuel, with clean natural gas and good service (change oil once a month) no issues

RE: Hydraulic roller lifter failure

(OP)
BCS
Without getting to far off topic. Are you getting new GM industrial engines or rebuilt? How many hours are getting on heads? Have you set any of the 8.0L or 10.3 gm engines yet? Sorry for the questions. I've spent the past 4 years selling new GM industrial engines and I'm curious.

Thanks

RE: Hydraulic roller lifter failure

new gm 5.7l industrials, run about 20,000 hrs or more before being rebuilt, haven't tried the 8.1l motors, from what we were told on them they lean out the back cylinders to bad from the tuned intake design making it to far of a run from the carb

RE: Hydraulic roller lifter failure

(OP)
Thanks BCS I was curious, thats about what we saw with 5.7L we sold.

RE: Hydraulic roller lifter failure

So what is the application for all these engines that run nonstop?

RE: Hydraulic roller lifter failure

At 1800 rpm? Has to be a 60Hz AC generator.

Mike Halloran
Pembroke Pines, FL, USA

RE: Hydraulic roller lifter failure

(OP)
Natural gas compressors

RE: Hydraulic roller lifter failure

Are you going to try a different manufacture of lifters now? I would suggest the OEM.

RE: Hydraulic roller lifter failure

That is if the OEM makes a solid roller lifter for this engine.

One other thought. Some roller lifters deliberately reduce oil to the top end by restricting the size of the oil feed hole in the side of the lifter and some cam/lifter combos cause a misalignment of the oil hole with the oil gallery if the base circle is not campatible with the lifter hole height.

Regards
Pat
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RE: Hydraulic roller lifter failure

There is no reason at all that the lifters have to be solid in this application. Solids are more for performance / race applications. And besides for a pumping engine you don't need or want the maintenance of solids, that is lash checks etc. OEM's have been doing the roller thing for years now and get good longevity from them.

RE: Hydraulic roller lifter failure

In my experience solids tend to be more durable and lighter and if set up right very rarely need adjustment. They certainly don't pump up if for any reason there is some valve train separation and as such can tolerate lower spring pressures. As there is some evidence this problem may be linked to spring pressures and valve float, a solid lifter will help this just as much as it helps a race cam overcome valve float and requirement for high spring pressures.

Regards
Pat
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RE: Hydraulic roller lifter failure

Does the engine run on the same natural gas it compresses?
I have heard that running on natural gas (and propane?) can cause binding of the valves in the valve guides - maybe this could lead to lifter problems?

RE: Hydraulic roller lifter failure

Are these engines running WOT at 1800 rpms? Any idea of what HP output is? Are failures mostly on the ex side? What kind of exhaust system? The recession is mostly the valve itself? What is tear down stem to guide clearance? Ever done egt?

RE: Hydraulic roller lifter failure

(OP)
Guy's
I haven't been answering questions because I've been deep into a different project and this has taken a backseat. I will try to answer the questions you have.

Dicer
These are existing blocks so we have to use retro fit kits on the lifters there is no OEM lifter. It seems for a standard retrofit lifter there is only one primary manufacturer. These engines are close to WOT at 1800, The failures appear to be a mix of intake and exhaust and not localized to a cyl. The recession is primarily in the valve seat. I haven't been able to get a head to teardown to measure yet. I haven't found any data that suggests an EGT study has been done

Clive
Yes the engine runs on the gas it compresses.

Pat
We really haven't had any discussion about going to solids. But that may be a good direction to test.

Thanks everyone for your suggestions.

RE: Hydraulic roller lifter failure

Have you done a metallurgical workup of the failed parts? The general tone of the conversation here seems to be that there is a lubrication failure. You should also look toward something like a fatigue failure of the bearing parts. If you get micro welding, what you might be seeing is the breakdown of the bearing metal at the surface with the tiny pieces that break out of the surface then becoming debris between the mating surfaces. The forces on these tiny pieces would be enormous, and they could be pushed into the surface, especially if they have strain hardened. There probably is not enough lubricant flow to wash the particles out efficiently, so they would tend to stay there. This could lead to the local welding you are seeing.

If this is what is happening, the fix could be pretty simple.

RE: Hydraulic roller lifter failure

Fredrick.

Valve float causes impact loadings. On fine needle rollers that causes very brief but extremely high local pressure at the surface of the rollers. The localised yielding can cause the case hardened surface to fatigue and crack and chip. I believe that is the most likely scenario you are indicating.

Another is that the normal manufacturing variations that inevitably occur results in some rollers being slightly more prone to the case hardening flaking than others and if they are loaded to the max, a few will be overloaded.

At least one roller follower manufacturer makes a very light weight slipper bearing rather than roller bearing roller follower. These where developed for use in engines where radical valve acceleration rates cause some valve bounce (valve train separation) and failed needle roller. They may be the answer in this case. Being slipper bearing, they need a bit more oil to the bearing between the roller follower and the axle it rolls on.

This article may help.

The plain bearing roller lifters are not mentioned so may no longer be available.

Extra oil feed lifters are listed.

http://www.iskycams.com/techtips.php

Regards
Pat
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RE: Hydraulic roller lifter failure

The OP said it's a needle bearing/axle welding problem. I think the needles would be 52100 steel, which is thru-hardened and not case hardened. If the steel is low quality and full of dirt/non-metallic inclusions, it would probably cause problems.

Easy enough for a met. lab. to check.

"You see, wire telegraph is like a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? Radio operates the same way: You send signals here, they receive them there. The only difference is there is no cat." A. Einstein

RE: Hydraulic roller lifter failure

Pat- that Isky blurb does say that the keyway-style plain bearing lifters are an extension to their product line (specifically for modified-lifter-bore-spacing blocks). The plain bearing EZ-Roll lifters are still available in tie-bar style for OEM-lifter-spacing blocks.

RE: Hydraulic roller lifter failure

No one has mentioned the increased weight of using Inconel material for the valves. That should influence the pressure recommendation. For what it's worth we've been adding another 30lbs to the seat pressure of heads intended for hydraulic rollers as compared to scuffer cams. Ford and Chevy small blocks are getting around 140 lbs on the seat and Big Block Chevy's and Big Block Fords are getting 175 lbs on the seats! (1.975 installed height). We generally use Shaver Specialty lifters, the extra pressure only helps. If you look at the issues involved the force of the spring is small compared to the impact if the roller should leave the lobe and slam back into place.

RE: Hydraulic roller lifter failure

I would bet that the lifters are not Crower, or isky. Give them a try.

RE: Hydraulic roller lifter failure

At 1800 RPMs, it is difficult to envision any situation where a hydraulic roller lifter could slam onto the lobe.

Also, why would an 1800 RPM engine need 175# seat pressures?

The Crower and Iskenderian performance lifters are several orders of magnitude more expensive than the typical rebuilder lifters. Yes, they're worth it for solid roller lifters on a one-off performance engine. No, they aren't affordable and really shouldn't be necessary for series-built hydraulic lifter engines.

jack vines

RE: Hydraulic roller lifter failure

How much they are worth depends on cost vs life vs downtime cost.

While they should not be necessary and 175# on the seat should not be necessary maybe (I don't know the cam grind) the fact remains they are failing in a way that is identical to valve train separation failures.

If to optimise for under 2000rpm running, the cam grinder used a profile with VERY short duration, but still high lift, the valves might have acceleration rates at 1800, similar to something designed for 7000rpm with much longer duration and similar lift.

Regards
Pat
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RE: Hydraulic roller lifter failure

Pat- if the lobes were that "extreme", the concave flanks would be clearly visible.

RE: Hydraulic roller lifter failure

I don't remember the shape of the flanks being mentioned and it quite possibly is not so extreme as to require a concave flank, but it still seems to need its 175 on the seat unless something else rather strange is going on.

Regards
Pat
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RE: Hydraulic roller lifter failure

OP>"It appears the needle bearings are microwelding to the axle assembly."<

If the problem were lifter bounce, I'd think it would show on the cam and roller OD.

"You see, wire telegraph is like a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? Radio operates the same way: You send signals here, they receive them there. The only difference is there is no cat." A. Einstein

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