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MG TD TF 1500 - lifters/cam/oil

About 5,000 miles on my engine. With motor out for restoring the rest of the car and the alleged lifer/cam problems I pulled the lifters. They range from perfect, to quite a number of pits in a small area in one. All appear to have been rotating. Have used Castrol 20/50Wt. The cam (from Abindgon spares- the "original spec" (which is really not) made by Crane with small lobes appears perfect. Options: use oil or additive with zinc (as in the long thread)and reuse the lifter, replace the worst lifters, replace all lifters, replace both the cam and lifters, or what? Kind of not good with the amout of pitting with such low mileage. Thanks in advance. George
George Butz

George

I believe the issue is likelt to be a manufacturing one, the material used was not properly hardened resulting in the surface breaking up. The original article blames SM street oils but these should not be used in high powered applications and proper break in procedure should be followed. ZDDP is also used as an anti oxidant and as such is used up over the oil change interval and it is at this point that there may not be sufficient ZDDP to act as an anti wear additive and rapid wear can develop.

I've copied a post by Martin, who is an Oil consultant with NORIA, on tribology


In Tribological terms (Tribology is a the study of movement between surfaces and includes lubrication) both the lubricant and the material will affect wear.

In terms of material, we see this in gear teeth in modernindustrial boxes, these are often tuff-trided and so have an extremely hard surface but it's like th shell on a hard-boiled egg - once penetrated breakdown is rapid. Whereas older gears were surface hardened to a good depth, hence many old boxes are still in use in indutrial plant whilst modern boxes seem to have a shorter life by comparison and are far less tolerant of dirt which often penetrates the surface to cause the rapid wear process. In the case of the tappets my belief is this is why cheaper tappets fail because they are like the hard-boiled egg, which is what I saw on the tappets from Phil's BGT after only a few thousand miles.

In terms of lubrication - firstly, one needs to understand the difference between the flat and roller followers. Flat followers have inter-related movement of sliding, whilst roller, as the name implies, are rolling. In thick film lubrication, the two forms differ in that sliding is hydro-dynamic lubrication (HDL) and rolling is elasto-hydro-dynamic lubrication (EHL) - but in both cases the correct viscosity is important, as is the additive package in HDL.

EHL works because the there is elastic deformation of the surface at the point of contact with the other surface and that in turn draws the oil into the contact zone between them. because the load is high and the contact area is small, the pressure experienced is very high, enough to compress the oil into a solid. Water does not compress into a solid, but oil does, and hence, although only a few microns thick, often around 1µm thick, the oil film is sufficient to separate the components and prevent damage to the surfaces. Obviously, 1µm is sufficient because rolling components such as the cam and follower, as with rolling element bearings, have very highly polished surfaces. Water and solids will disrupt the film, and hence you see pit marks on rolling surfaces caused by very small, hard particles penetrating the surface under the crushing, rolling action. Generally additives are not an issue here and hence the reduced need in modern cars for the zinc, more of which I will explain shortly.

HDL, or sliding lubrication, works because, like water skiing, the component experiences enough speed at the appropriate load to actually ride on a film of oil, thus being separated from the other surface and eliminating surface-to-surface contact, consequently eradicating wear. I won't say it eradicates friction as fluid friction is at work, and the higher the viscosity, the higher the fluid friction. The lower the viscosity, the lower the friction, but the less load that the oil film can support. (Of course we could get into a lenghty discussion here about the benfits of synthetics and the greater load they can support at lower viscosities compared to mineral oils, especially low cost oils!) HDL does depend on the right speed and viscosity, and therefore, when cold the oil has a huge drag on fluid friction terms. Also, of course, in an engine the speed varies accordingly, and at very low speeds during start-up, the follower is in direct contact with the cam. Therefore, additives are added to protect the engine until sufficient oil is fed to the surfaces to provide HDL on flat tappets.

Anti-wear or AW additives are friction modifiers. Friction modifiers are formulated to work at varying temperatures, so in the basic form, fatty acids are used but these only really control friction up to about 70-80°C contact point temperature. Beyond this AW are used and these usally compromise Zinc and Phosphorous in a form know as Zinc DialkylDithioPhosphate aka ZDDP. These work up to a contact temperature of around 130°C and beyond that Extreme Pressure (EP) is used.

In both the case of the AW and the EP, the additives that are coating the surfaces will react under temperature causing the surface to go ductile. The analogy I can best use here is comparing rubbing two blocks of soap - when dry there is friction and wear, but when coated in water there is much reduced friction and wear (and hence the Tribologist's favourite joke is about the Nuns and where's the soap! Oh, and of course the joke about KY jelly being Y2K compliant!).

This ductile surface is soapy in nature and thus movement is improved with reduced friction and wear. However, aggressive AW/EP can lead to polishing which results in the flat surface going concave.

It would be easy enough to distinguish between additive polishing and wear as a result of lack of lubrication and protection, since the former will be a highly polished surface, whereas the latter would be micro-scratched in the direction of the movement, possibly with bluing as a result of the high temperatures. It has to be said that additives are really only necessary if there is direct contact between the follower and the cam, and also that the follower is generally designed to be sacrificial so that wear takes place on the follower rather than the cam.

So in terms of the reduced Zinc in oils, this may be a cause for concern on flat followers, but using the appropriate oils can reduce this risk. Ensuring that the oil's viscosity is right will aid the start-up circulation. Using clean oils, too. Avoid the use of aftermarket additives that are generally an aggressive form of AW additive as these can also result in high levels of polishing and will damage the tappet face.
Paul

Thanks Paul,

This really is a great informative piece. I feel like I know what I want to do with my engine (and any 'B' series engine I work with) and that will be to run Valvoline 20w 50 racing oil, which while expensive, will provide the AW package you write about.

George,

I would run the engine some more and watch the wear on the lifter you've noted. Since the lifter is sacrificial, you won't hurt the cam in doing so. You can just listen for a noisy valve... if you have to adjust it too often, you may need to replace that lifter. If your cam has a different profile, pay attention to the bottommost oil way in the lifter, it may need to be lowered to assure oil flow to the cam/lifter interface. Are your rocker arms reconditioned? If there is a concave shape to the interface between the rocker arm and the push rod, you may need to compensate for that when you adjust your valves. I use the somewhat maligned 'clik-adjust' for that purpose.

warmly,
dave
Dave Braun

George

Read the thread nNew oils bad for our cars. It sounds like you could be in this category. It appears that we need to be very careful on using the new formulation of oils.

The thread has some recommendations for oils with the needed additives or additives you can add as a seperate product.

I would also think about contacting Delta Cams in Tachoma WA. They have very good experience in regringing TD lifters and can probably reface yours.

Delta Cam
1938 South Tacoma Avenue, Tacoma, WA 98402
(253) 383-4152
BEC Cunha

Also - http://www.deltacam.com/
David DuBois

Dave D that is the wrond URL Larry
L.A. Leclerc

Dave

I tried that one earlier and noted it is no longer working. I am hoping that does not mean that the company has gone away also. Can you give them a call and get the details on why the web id gone?
BEC Cunha

Hey...thanks, I just won a free laptop as the 1,000,000 visitor.....what a great New Years!!!!!
gblawson - TD#27667

Lifter wear? What lifter wear. New Roller Lifter Cam kits now avalible. All custom ground. Contact me, off line. E mail / or 914 420 8699 E.S. T. Len
Len Fanelli

I have a 1952 TD, and I've been advised to use Marvel Mystery Oil. I'm currently using Castrol 20-50. I have also seen some pretty cogent arguments for using Rotella tractor oil. Does anyone have any good info on the use of either of these lubricants?
Thanks
Carlos
C.R. Diaz

Carlos

Oil chemistry is too complex to start adding aftermarket additives, unless for break in. If looking for more ZDDP HDEO Bike and Race oils tend to have more than standard PCMO
Covered at this site
http://www.lnengineering.com/oil.html
At one extreme
http://www.joegibbsracingoil.com/datasheets/81106.php
Amsoil suggest SM levels are OK
http://www.amsoil.com/dealer/techservicesbulletin/TSB_flat_tappet_and_camshaft_lube.pdf

However Amsoil are like:y to be using modern oil additive technology not cheap but effective ZDDP. What you're going to see are new ashless antioxidants and AW/EP adds come into play now, such as alkylated diphenylamines (antioxidants), hindered phenols (antioxidants), and new AW adds such as boron esters, concentrated calcium and synthetic AW/EP adds (such as new esters). A newer type of zinc antioxidant/AW additive is ZDTC, or Zinc dialkyldithiocarbamate, which is similar to Moly DTC and Antimony DTC, and only varies as to the metallic element.

Paul

This thread was discussed between 31/12/2006 and 05/01/2007

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