Odd Lifter Wear Pattern
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Thread: Odd Lifter Wear Pattern

  1. #1
    Opel Rallier since 1977
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    Odd Lifter Wear Pattern

    In getting our 'new' '75 1900 up and running, we pulled the lifters out to clean out any water that might have been in there. (As an aside, the engine had about 1/2 cup of water and/or AF in the crankcase that was fully separated and a bit of water in the oiling system but it did not look like it had been run hardly at all since the water/AF entered. The car set for several years and we are convinced from various evidence that the hood was open or off for a while, based on where we found water and rust.)

    The odd thing about the lifters was that all 4 intake lifters showed some wear and are starting to go concave, while all 4 exhaust lifters showed little or no wear. I have had a fair number of these engines apart and recall seeing the same type of wear on some lifters, but cannot recall finding any particular pattern on the intakes vs. exhausts. But I may not have paid attention before. (And it has been over 20 years since I was 'active' on these engines, so I've forgotten a lot LOL.)

    I looked at the stock installed spring pressures and see nothing really different between exhaust and intake spring pressures. (And I am assuming this still has the stock cam and springs.) So any experience or ideas on why this is so, would be appreciated.
    Last edited by Manta Rallier; 07-05-2019 at 10:59 AM.

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    3000 Post Club Site Supporter P.J. Romano's Avatar
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    Check to be sure that the springs on intake and exhaust valves were not swapped. Springs on intake valves are taller and those on exhaust valves are shorter as they sit on rotators. Also, they are slightly tapered.

    You might also like to check springs pressure. It should be 93 lbs (42 kg) for intakes at installed height of 40 mm and 97 lbs (44 kg) for the exhaust side.

    By the way as the lifters are worn, the cam is likely toast as well.
    Last edited by P.J. Romano; 07-05-2019 at 01:16 PM.
    Ooooner and soybean like this.
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    Opel Rallier since 1977
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    Tnx for the thoughts. Actually, I was thinking the exhaust rotators might be doing some good and helping the exhaust lifters... but the I remembered there are no pushrods here LOL. Next time in, I'll look at the springs.. not likely IMHO, but with the mucking around that one or more of the PO's has done, who knows. BTW, cam lobes all looked normal, so I think we have gotten to this in time. I've seen this type of lifter wear many times in the past... just never noticed it being on just one set of valves.
    soybean likes this.

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    Opel Rallier since 1977
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    And one update: I checked the intake lobe lifts today, and the #1 was a few thousandths lower than the other 3, and the #1 lobe iss juuuuust starting to show a bit of a flat spot on the peak of the lobe..... what I have seen to varying degrees when the lobe is 'going'. This flat spot is pretty narrow, adn the loss of lobe lift is only a bout .003" but P.J. got it right to be suspicious of the cam being on its way to oblivion. The depth of concavity looks to exceed .005" on all of the intake lifters.

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    3000 Post Club Site Supporter P.J. Romano's Avatar
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    Some time ago I have downloaded the following article somewhere from Internet. You might find it useful.

    Failure Criteria associated with Cam and Cam-Followers

    Surface-initiated Fatigue
    This begins with reduced lubrication regime and a loss of the normal lubricant film. The oil film is reduced to boundary or a mixed regime. Some metal-to-metal contact and sliding motion occurs. Surface damage occurs. The high points of the metal surface asperities are removed, which initially appear as a matted or frosted surface. This type of surface damage is usually visible with a magnification of three to five times.

    Note, the term "contact fatigue" is not used by ISO. This is a vague term sometimes used to describe both forms of fatigue. It does not specify whether metal flexing damage started in the subsurface or from some initial surface damage. It encompasses any change in the metal structure caused by repeated stresses concentrated at a microscopic scale in the contact zone between the rolling elements.

    A cam can be considered to have failed when the payload's motion does not repeat reliably due to the effects of wear of the cam at the contact surface between the cam and the cam-follower. Cam and cam-followers can fail in a number of ways. The main modes of failure are:

    • Pitting
    • Scuffing
    • Polishing


    Cams with roller followers will usually fail by pitting. Cams with sliding followers can fail in any of the above modes.
    Each failure mode has a failure mechanism. There are desirable material properties to prevent each failure mode.

    Pitting Failure and Material Strength

    Contact conditions give high surface stresses. The stress must be kept below a critical value to avoid yield or the onset of plasticity. However, since the cam is continually loaded and unloaded, we should expect that the steel will fatigue at a level of stress that is less that the yield stress. The fatigue limiting contact stress (Endurance Limit) is a function of, mainly, the hardness of the steel. The stresses must be kept below a critical value called the Permissible Contact Stress.
    If these conditions are not met, then fatigue failure will occur in the form of pitting. The pitting produces a surface roughness due to the braking out of flakes and spalls. A material with high fatigue strength will have a good resistance to pitting.

    Pitting occurs only after a large a number of repeated loading where the oil film breaks down because of zero sliding velocity - if a sliding cam.

    Pitting is classified as contact fatigue which is subdivided into three general modes: pitting (macropitting), micropitting and sub-case fatigue.


    Macro-pitting
    Macropitting is divided into specific modes or degrees, including initial pitting, progressive pitting, flaking, and spalling.

    Initial Pitting
    Small pits less than 1 μm in diameter. They occur in localized areas and tend to redistribute the load by removing high asperities. When the load becomes more evenly distributed, the Macro-pitting stops.

    Progressive Pitting
    Characterized by pits significantly larger than 1mm in diameter. Pitting of this type may continue at an increased rate until a significant portion of the cam surface has pits of various shapes and sizes.

    Flake Pitting
    Triangular pits that are relatively shallow but large in area. The fatigue crack extends from an origin at the surface of the tooth in a fan shaped manner until thin flakes of material break out and form a triangular crater.

    Spalling
    Progressive pitting where pits coalesce and form irregular craters that cover a significant area of the cam surface.

    Micro-pitting
    Cam surface appears frosted, matted, or gray stained. Under magnification, the surface appears to be covered by very fine pits, less than 20 microns deep. Metallurgical sections through the micro-pits show fatigue cracks that are inclined to the surface at an angle of less than 45 degrees. The cracks may extend deeper than the visible micro-pits. Micro-pits occur most frequently on surface hardened cams although it may also occur on through hardened cams.

    Micro-pitting is a Hertzian contact fatigue phenomenon and it is a form of localised material surface damage that occurs under rolling and sliding contact when the parts in contact are operating in elastohydrodynamic (EHL) or boundary lubrication regimes. The pitting of a cam is considered to be a fatigue phenomenon that results from the contact stress at the surface and or the maximum shear stress below the surface.

    The stress field is complex because it is a function of the Hertzian contact stress, stress at roughness asperities, stress because of metal inclusion stress raisers, and also residual stresses with the cam from heat treatment and or machining.

    Initial micro-pitting can often start by the removal of high-spots of surface roughness asperities or machining errors, to form cavities. Micro-pitting can often stop once the high spots are removed. In most industrial application, initial-pitting that does not progress beyond a matt and grey finish is deemed to be not that serious. Micro-pitting can also start at small surface or subsurface cracks that are very small compared to the contact zone.

    The small micro-pits are approximately 10 – 20μm deep, 25 – 100μm length and 10 – 20μm width.
    When pits merge, and the pit becomes larger, they are more often called a spall. If it continues it results in reduced cam accuracy, increased dynamic loads and noise.
    The removed of cam material can itself also damage the cam-follower bearing unless it can be eliminated with lubricant filtration.
    Micro-pits appear in case-hardened, nitrided, induction-hardened, through-hardened, and of course, cams that are not heat treated.

    Sub-case Fatigue
    Origin of the fatigue crack is below the surface of the cam in the transition zone between the case and core. Fatigue beach marks may be evident on the crater bottom formed by propagation of the main crack.

    Scuffing and Polishing Failures.
    There should be lubricant to separate the cam and cam-follower. The film thickness that is needed depends on the surface roughness of the cam and the cam-follower.

    With sliding contact, there may not be sufficient film thickness for part of the machine cycle when the relative velocity between the cam and cam follower reduces to zero or reverses. If this occurs, then materials must be chosen carefully in order to withstand the scuffing.
    Sliding contact with a thin film can produce different wears patterns:

    Scuffing
    It occurs at high speeds when adequate lubrication is not provided by the elasto hydrodynamic action.

    Lack of lubrication causes high sliding friction. High tooth loading and high sliding velocities that produce a high rate of heat in the localized contact region causes welding and tearing of surfaces apart.
    Scoring can often be prevented by directing adequate flow of appropriate lubricant that maintains hydrodynamic lubrication.

    Surface finish is also an important factor for scoring. Surface finish as fine as 0.5μm cla is desirable to avoid scoring.

    Scuffing is an 'Adhesion Phenomenon'. This is severe wear. Small portions at the surfaces of the cam and cam-follower weld together at asperities. The resulting surface is roughened. The scuffed area appears to have a rough or matte texture. Under magnification, the scuffed surface appears rough, torn and plastically deformed. Scuffing is not a fatigue phenomenon and it may occur instantly.
    Certain materials combinations can resist scuffing better than others. This might be because they are chemically dissimilar or one or both of the materials contains a lubricant - for example graphite flakes. Frequently, when either the cam or the cam-follower is harder by approximately 2-3HRC (Rocker Hardness C scale), then scuffing is reduced.

    Polishing
    This is less critical wear. There is contact only between peaks of the surface roughness. This can result in the surfaces becoming smoother so that wear might stop. The wear might continue indefinitely so that a large amount of material is removed from the cam or follower.

    Plastic Flow
    Plastic Flow is cold working of cam-follower and cam surfaces caused by high contact stresses because of the rolling and sliding action. It is a surface deformation that results from the yielding of the surface and subsurface material and is usually associated with softer cam materials, although it also occurs in heavily loaded case-hardened and through hardened cams.

    Cold Flow failure, where the surface and sub-surface material shows evidence of metal flow. Surface material has worked over the sides of the cam giving a winged appearance.
    soybean and SpringGT like this.
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    4,000 Post Club norbertone.gt371's Avatar
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    The last week I have the discusion here about this micro pitting by overload pressures by the Hertzian phaenomenon.
    I must find out,that most primary part of all hydro lifter is the gap measure for the leak rate. Oh and the wight from the lifter too.
    Both must fit exacly to the cam and the open ramp design you used.I never know that before that those gap is so critical.
    I must sleep at shool when the teacher told it

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    Thanks guys: I always like to read highly technical stuff like that and will do so. But looking at the above post at a glance, it does not explain why this particular wear situation occurred only on the intake lifters and not on any of the exhaust lifters. I cann't think of any difference except for the rotators on the exhaust side, and how that could translate to lack of wear in this setup is not clear. The Stock spring loading closed and open is almost identical.

    It is not super critical... just more of a point of interest.

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    Quote Originally Posted by Manta Rallier View Post
    Thanks guys: I always like to read highly technical stuff like that and will do so. But looking at the above post at a glance, it does not explain why this particular wear situation occurred only on the intake lifters and not on any of the exhaust lifters. I cann't think of any difference except for the rotators on the exhaust side, and how that could translate to lack of wear in this setup is not clear. The Stock spring loading closed and open is almost identical.

    It is not super critical... just more of a point of interest.
    The wear on your engine is pretty odd, i have a 74 Manta and get this....
    i had a miss i couldn't get rid of a while back, come to find out later
    (after removing valve cover) that the intake valve on 2nd cylinder from
    front of engine was not operating, checked cam lobe, and it appears flat,
    and lifter is dished...so how do i get just one lobe that went flat?? Weird, if it is a lubrication problem,
    you'd think it would affect more than one.

    Oh well, good excuse to wake up my beloved Manta!!

  11. #9
    Opel Rallier since 1977
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    Well, when you get wear on a lifter past a certain point, it just very rapidly destroys the lobe. Also, if the lifter hangs up and stops rotating for some reason, the same disaster will follow. Or the lobe can just fail. It can and does happen on one lifter/lobe; I'd expect that the happen most often.

    Also, if you are not using a ZDDP fortified motor oil, then it adds to the risk of lifter & lobe wear.

    Be aware that you have a LOT of miniscule metal particles in your engine now. If you are going to even contemplate just replacing the cam without a teardown to clean it all out (which I would not do), then it is going to need a lot of flushing (like with diesel) and cleaning now. You don't want that in the engine. If it gets picked up, the first thing it gets to is the oil pump, BEFORE the oil reaches the filter.... which may not catch the tiniest metal particles. At least flush it a lot and take the pan off and clean that out 100%. And take off the oil pump cover and look at it and the pump gears.
    kwilford likes this.

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