article: new oil & flat tappets

[tdr1919]

I was reading a recent addition of Corvette Fever about the "modern" oils on the market missing key ingredients which prevent the wear of the (non-roller) flat tappet lifter against the cam shaft. This ultimately prevents the tappet from rotating and causes premature wear of the cam shaft. I was even more shocked when I read that synthetic oils are too slippery and prevent the cam shaft from rotating the tappet, ultimately causing premature wear of the cam. The article proceeded to recommend using diesel rated oils, racing oils or additives such as a break in additive when you are installing a new cam.
Any opinions / feedback?
- Tom

 

[motorman]

I was reading a recent addition of Corvette Fever about the "modern" oils on the market missing key ingredients which prevent the wear of the (non-roller) flat tappet lifter against the cam shaft. This ultimately prevents the tappet from rotating and causes premature wear of the cam shaft. I was even more shocked when I read that synthetic oils are too slippery and prevent the cam shaft from rotating the tappet, ultimately causing premature wear of the cam. The article proceeded to recommend using diesel rated oils, racing oils or additives such as a break in additive when you are installing a new cam.
Any opinions / feedback?
- Tom

i have been running mobil1 in my 1988 chevy PU for 20 years and it has hyd flat tappet camshaft and so far no camshaft problems. the aftermarket camshafts with heavy valve springs had the biggest problem because they no longer "parkerize" their camshaft unless you pay extra. you should always use a additive like GM EOS with any new camshaft but once the break in period is over oils like mobil 1 should not be a problem

 

[Itshakes]

New Oils and Flat Tappet Cams

I have used Mobil 1 in all the toys that have gas burning engines. I have used this oil since 1979. I owned many Corvettes with flat tappet cams, and NEVER had any problems. I also own a Buick Regal with a turbo charged engine. It has 130,000 miles on it and all the equipment under the hood is ORIGINAL. This car [along with ALL the other "toys'] still runs strong, and does not make ANY lifter/piston noise. It still runs the quarter mile in 12.66 @ 102 MPH. There is over 300 runs on this car!!

Nuff' said!

 

[Hib Halverson]

While it is true that the extreme pressure lubrication properties of many engine oils began to change in the mid-1990s and changed significantly in the early 00s, the recent story in Corvette Fever magazine did as much to propagate myths and dispense incorrect information about how current oil blends affect valvetrain wear in engines with overhead valves and flat tappet cams as it did to dispel some of the rumor and urban legend about those subjects.

In the above referenced article, Corvette Fever said that synthetic engine oil is "too slippery" and that prevents lifter rotation.

It is, in my opinion, inexcusable for a magazine which fashions itself as a technical reference for the Corvette enthusiast community to publish such a distortion of fact. That said, I’m sure the magazine didn’t do that intentionally. It is possible this happened due to poor research and inadequate fact-checking, problems which are far too common in the car magazine business these days.

Some in media must think that, during the 90 or so years pushrod valvetrains have been used in automotive engines, engine manufacturers have never done any research. They choose believe the wild-assed-guess some knucklehead engine rebuilder makes when confronted with a camshaft failure—that the root cause was the synthetic oil in the engine being too slippery?! Oh please...spare me.

To some people who understand engine oil, the chemical and mechanical processes at work inside a running engine and, specifically, lubrication at the lobe/lifter interface in a flat tappet valvetrain; the idea that any oil could be "too slippery" and such "excessive slipperiness" interferes with the mechanical action which causes lifters to rotate is laughable...it’s pure nonsense.

A 1992 SAE paper GM issued offers information about oil film thicknesses and frictional properties. It said that there are two cam angles where there is zero oil film, but most cam angles have some oil film. This paper also indicates that, if the friction of the follower in the bore is greater than the cam lifter friction, then slip will occur. While, in theory, that slip could occur, in practice, as long as the engine has no mechanical problems, the friction at the lobe/lifter interface will always be greater—much greater, actually—than friction between the lifter bore and the lifter. Remember: the same oil is lubricating the cam/lifter contact and the lifter/bore contact.

A second paper, published by Ford, indicates that lifter/bore friction is about 13% of total at low speeds and goes down to about 2% at higher speeds. Those numbers in mind, in theory, you would need a reduction in friction of nearly 80% with synthetic oil for slip to occur. With synthetic oil compared to petroleum-based oil, you can see reductions in valvetrain friction of, at most, 10%. So, in theory, it ain’t gonna happen. Oh, but forget the theories. In practice, even if there was the necessary 80% difference in friction between synthetic and petro-based oil, for that difference to result in slip at the lobe/lifter interface, you’d need to have the lobe lubricated with synthetic and the lifter lubricated with conventional oil which is, of course, impossible.

With respect to lubrication at the lobe/lifter interface when the valvetrain is highly loaded, it is not a film of oil which prevents metal-to-metal contact. It is a near-monomolecular layer of iron sulfide and iron phosphate which provides the extreme pressure lubrication necessary to prevent rapid wear.

Iron sulfide and iron phosphate form when the sulfur and phosphorous resulting from the breakdown of zincdithiophosphate (ZDP), blended into the oil as an extreme pressure additive, combine with the iron of the cam and lifters. At the lobe/lifter interface, temperature and pressure cause ZDP to break-down into alcohol (which evaporates), zinc (most of which washes away), sulfur and phosphorous. Those last two chemicals combine with the iron molecules on the surface of the lobe and and the face of the lifter to make an extremely thin layer of iron sulfide and iron phosphate and those two compounds provide the necessary lubrication.

Most of the oil is actually "squeezed" out or wiped away and under some conditions, there is virtually no oil film at all. The sulfur and phosphorous provide lubrication in a process which "trades" chemical wear for adhesive wear, thus preventing failure of the lobe and lifter.

Since, in a practical sense, there's no film of oil available to be "too slippery", there you have further evidence that an engine which suffers problems with lifter rotation can not have this "slipperiness" as the root cause of the problem.

Ok...so what can cause reduced or lack of lifter rotation?

It could be a camshaft with lobes already worn due to other problems such that they have inadequate taper left to cause lifter rotation. It could be a lifter already worn such that it's convex surface (which also facilitates the rotation) has become "flat". It could be that either the cam or the lifter, or both had manufacturing defects such proper lifter rotation didn't occur. It could be that the cam and/or lifters experienced rapid wear due to improper installation.

It could be a block with worn or damaged lifter bores. It could be liters with worn or damaged "barrels". It could even be a block that was machined incorrectly such that the lifter centerlines are not offset far enough from the centers of the lobe surfaces for adequate liter rotation to occur. Admittedly, that last scenario is a bit far-fetched but it could, in theory, occur.

But...if a flat tappet engine has lifters that don't rotate, it's not because an engine oil was "too slippery".

I hate to say this because, in years past, Corvette Fever has been a customer of mine, but...in my opinion, its publishers need to take steps which could prevent such myths being published "as fact" in technical articles. If the magazine is incapable of that, then I think that, perhaps, it should do the Corvette hobby a favor and confine its content to car features and event coverage.

 

[LORR1943]

Flat tappets and new oils

I am an AMSOIL dealer in Houston, Texas, and the reason some cam and lifter manufacturers specify an additive is because a few years ago oil companies under pressure of the EPA, quit putting ZINC CHROMATE in their oils. ZINC is very difficult to compress and makes a great barrier in applications where metal is squeezed together, as in a cam and flat surface lifter, or a gearset, as in a differential. If you are running a flat tappet cam and lifter configuration, and you prefer synthetic lubricant, find one with ZINC in it and you will never have to worry.
The only caution I would offer you is in a brand new or rebuilt engine, never "break-in" the engine with a synthetic oil. Use an organic(conventional),low viscosity, oil for about 5 hours or 300 miles, then change the oil and filter with the synthetic of your choosing.
New Z06 Corvette engines are "broke-in" at the engine plant before ever being shipped to Bowling Green for installation, and they are shipped with Mobile 1. Bear in mind that most engines since the early '80s came with roller lifters and non-tuftrided cams(soft).
In case you are interested, AMSOIL was the first 100% synthetic oil produced in the USA for automobiles, 35 years ago!
For more info go to: www.AMSOIL.com. There is a wealth of info there.
Thanks! Larry Orr.

 

[Hib Halverson]

There is a huge amount of inaccurate information in the post above.

First...It's not "Zinc Chromate"---that's an anticorrosive agent used in paint, most commonly, paint for aircraft. It's "zinc dialkyldithiophosphate" or "ZDDP" (also "zinc dithiophosphate", "ZDP" or, as many incorrectly say "zinc")

Second...When zinc dithiophosphate is compressed and heated at the lobe/lifter interface, it quickly breaks down into alcohol (which evaporates), zinc (which washes away), sulfur and phosphate. It is the sulfur and phosphate which combine with the iron molecules on the cam lobe and the lifter face to make iron sulfide and iron phosphate, the two chemicals which do the vast majority of the extreme pressure lubrication.

Third...ZDP has not been removed from oil. That is harmful disinformation propagated by the additive business with the intent of marketing their products by misleading potential customers. Reality is: in some cases, it's been reduced by about 35%, but in other cases the ZDP content is unchanged and has remained so since ZDP was first blended into engine oil in the mid-1950s as an EP additive.

Third...it was not the EPA which forced some reduction of ZDP in certain types of engine oil, it was the car companies.

Fourth..."New Z06 Corvette engines" are not "broke-in" at the plant.

Fifth...the change to roller lifters was made in Corvette for the 1987 model year and those roller cams are in fact, harder than flat-tappet cams because they are steel billets rather than cast iron.

About the only correct statement in the above post is that, in fact, it was AMSOIL, which produced the first synthetic engine oils for automotive use.

 

[LORR1943]

Answer to above post.

I can only say that by my not being a professional writer, or an expert on mid-eighties GM camshafts, or an expert on the GM build/test process on the LS7/Z06, or the oil used in automobile engines for the past 50 years(I'm 65)or I'm also not a chemist, has left me with limited knowledge about all those things! HOWEVER, I submit to the writer of the original thread, get yourself a good quality 100% synthetic oil with Zinc allready added in, and you and your cam will fair very well, as long as you don't drink the oil!

 

[Hib Halverson]

(snip)I submit to the writer of the original thread, get yourself a good quality 100% synthetic oil with Zinc allready added in, and you and your cam will fair very well, as long as you don't drink the oil!

"LORR1943" gets the Sunday morning "Beacon of Reality Award".

 

[WhalePirot]

good article from Comp

I found this piece informative and is applicable here.

http://www.compcams.com/Base/pdf/FlatTappetCamTechBulletin.pdf

I heard some buy 'diesel oil' for the increased zinc-whatever.