Hydraulic roller lifter failure 1

[Fmangas]

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.

 

[patprimmer]

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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[Metalguy]

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

 

[pontiacjack]

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.

 

[patprimmer]

OK PJ. I missed that.

I feel thw EZ roller (I had forgotten the name) should solve this problem

Regards
Pat
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[AboveRedline]

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.

 

[dicer]

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

 

[PackardV8]

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

 

[patprimmer]

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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[pontiacjack]

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

 

[patprimmer]

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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[Metalguy]

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