lifters rotating

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is there any truth to the rumor that a syn oil will not allow the lifters to rotate properly and cause uneven and excessive wear on a flat tappet type engine.
 
There is some evidence a lot of the new oils are having trouble with just that. Amsoil has just redone their 10W40 and 20W50 with the high Zinc formula's for that issue.
 
I haven't heard of this one. Now, in a related like action, I have heard of roller or ball bearings "sliding" as opposed to staying in motion ..which causes wear when it does plow through the film in a squeegee like action.
 
In all my training, I've never heard of the lubricant as being the cause of skidding in a roller bearing. Skidding has always been attributable to high angular accelerations combined with low loading on the components. Never have I heard the term "too slippery" attributed to a lube at my company.
 
I'd be an effect of friction coefficient, which can be dialed in regardless of the base stock type. Think a lot of these things were created by the early synthetic oil marketeers and all there grand claims of better mpg, more hp,engines not breaking in etc. Built a mental image in peoples minds of super slippery oil. It is true some synthetic base oils have less traction, but who runs straight base oil in their engine?
 
Originally Posted By: Kestas
In all my training, I've never heard of the lubricant as being the cause of skidding in a roller bearing. Skidding has always been attributable to high angular accelerations combined with low loading on the components. Never have I heard the term "too slippery" attributed to a lube at my company.


I didn't say that I attributed it to the lubricant itself. I merely related that this is the only time I've heard of such an action.
 
Think you can just look at the oils hths spec and see how much "traction" it will have? Better indicator than trying to guess by basestock and additive numbers. What's best is probably application specific (friction reduction or traction).
 
Good question. I won't comment on it now but will post some more things for us to educate ourselves with so we can come to better conclusions. I just Googled "traction coefficient HTHS"
http://www.lnengineering.com/sae/Design%...007-01-4143.doc
http://www.springerlink.com/content/uk687u424847t025/
http://www.patentstorm.us/patents/5962381-description.html

EDIT: this link seems to hit the nail on the head. The answer appears to be that using HTHS alone is not good enough for traction coefficient estimation in the valvetrain. http://journals.pepublishing.com/content/y252327m78363270/
Quote:
The work also enabled estimates to be made of the proportion of hydrodynamic and boundary friction in the engine, since the vast majority of boundary lubrication occurs in the valve train. Knowledge of the ratio of boundary to hydrodynamic lubrication was found to be important since the two key lubricant parameters that can be varied are (a) viscosity and (b) the introduction of a friction modifier additive. The viscosity of the lubricant will affect the hydrodynamically lubricated parts of the engine whereas the presence of a friction modifier will reduce boundary friction in the engine.
 
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Valve trains still seem to rely primarily on thicker oils for protection, moly reduces friction but it doesn't necessarily reduce wear, ZDDP is still the best 'common' anti-wear additive, OEMs trade off wear vs low viscosity with low friction additives, bearing wear correlated with visocisty, etc.., all the things that we learned in kindergarten :^)

The http://lnengineering.com/sae/ link has some nice briefs.


http://sciencelinks.jp/j-east/article/200114/000020011401A0391179.php

Friction Analysis between Cam and Shin in Engine Valve Train System.

Abstract;A friction measurement apparatus has been newly developed to analyze the frictional behavior between a pair of a cam and a shim in a direct acting valve train system. This apparatus has enabled the real time measurement of frictional force during the rotation of a cam shaft by placing a tri-axial transducer between the shim and lifter. Frictional behavior between the cam and shim has been evaluated using commercial engine oil. Most of the contact regions, that is, the ramp, shoulder and nose part, exhibited frictional coefficients from 0.1 to 0.15. These regions are judged to be under the boundary lubricating condition due to the theoretically confirmed low oil film thickness. Only the contact area of the flank part showed a low frictional coefficient of around 0.05, due to the thick oil film under the elastohydrodynamic lubricating condition. The influence of an organo-Mo-type friction modifier(FM) added into the engine oil has been investigated. It was determined that the organo-Mo-type FM effectively decreased the friction between the cam and shim by means of reducing the friction in the boundary lubricating region. (author abst.)



http://www.lnengineering.com/sae/Design%...007-01-4143.doc

SAE Technical Paper Series. Design Considerations in Formulating Gasoline Engine Lubricants for Improving Engine Fuel Economy and Wear Resistance Part 1 Base Oils and Additives. 2007-01-4143

19. Adequate performance for a lubricant in the VIB sequence is most important to most OEMs as this is a good indicator of fuel economy, after which sequences to evaluate the wear performance are then considered.
20. These new lubricants must balance the fuel economy improvement FEI% and good wear resistance.
23. As speed increases, the coefficient of friction decreases, with Group IV oils having the lowest and Group II oils the highest but has little effect of the FEI %.
34. The poor performance of MoDTP and MoDTC-1 has to do with the interaction of ZDDP which leads to a decrease in tribofilm hardness even though these tribofilms were the thickest and fastest to form.
36. The base oil has no significant relationship on wear other than a slight improvement with oils with more methyl groups, which help to contribute carbon to the anti-wear tribofilm with a significantly lower wear coefficient.
37. But base oil does have an effect on hydrodynamic friction which viscosity and film thickness which is good for wear, bad for FEI.


SAE Technical Paper Series. Engine Oil and Bearing Wear. 810330.

1. There is a dependence on oil viscosity on bearing wear.
2. Bearing wear can be divided into two categories: catastrophic and non-catastrophic (normal wear and tear).
3. “The best correlation was found between connecting rod bearing wear and pentane insolubles.”
4. The bearing distress tests measured not in bearing weight loss but in bearing demerits were precise enough to allow researchers to differentiate between a 5W-20 and 10W-40 oil, showing sensitivity towards viscosity of oil used.
5. Average connecting rod bearing wear demerits for the 5W-20 was 133+/- 37 versus 55 +/- 4 for the 10W-40. TABLE 2.
6. Bearing distress in tests with Newtonian oils (mono-grade) were lowest with oils with higher viscosity at 100C and 150C.
7. Increase in oil viscosity showed a linear decrease in bearing wear demerits with data collected precise enough to determine a zero wear intercept of 13.7 cP at 150C. FIGURE 2.
8. Bearing wear is directly proportional to the HTHS viscosity of oils.
9. Bearing distress test wear was higher with multi-grade oils than their mono-grade base oils, so the additive packages used must have some effect on an oils performance.
10. The detergent type used was the largest contributor to performance of oils in the bearing distress tests.
11. TAN or total acid number of oils tested showed poor or no correlation to connecting rod bearing wear from corrosion.
12. As average sludge merit decreases there is an equal response in decreased bearing wear.
13. Under severe conditions the detergent inhibitor package can contribute to bearing wear.
14. Pentane insolubles were highest in 100% ester (Group V) oils in first drains.
15. Low ash-less dispersant oils showed highest average total connecting rod bearing weight loss.


http://physicsworld.com/cws/article/print/5020

But by combining models for the plain bearings, the piston [censored] and the valve train, researchers have found that they can model the lubrication conditions in a complete internal combustion engine. Since the bearings and piston rings are lubricated predominantly in the hydrodynamic regime, a lubricant with a lower viscosity should lead to a thinner oil film and thus lower friction. However, the valve train operates in the mixed-boundary lubrication regime, which means that lower friction can only be obtained with thicker lubricants. Engine-friction models enable us to study the trade-off between viscosity and friction, and therefore select the optimum lubricant to improve a vehicle's fuel economy
 
In layman's terms please. Does synthetic oil hinder lifter rotation? Also, been running delo 15w40 in my pontiac 400. According to this info, would a 20w50 offer more protection to a valvetrain with high spring pressure(330# plus)in my pontiac with CC274XE cam?
 
We've had this discussion here in the past, and IMO a lot of issues aren't actually lubricant related but come back to poor QC in lifters and cams.

The lifters often don't have the correct radius to ensure rotation, and the cam lobes the corresponding correct taper.

If these are OK, then it becomes a viscosity and EP additive issue, not a base oil issue.
Often the cam/lifters aren't run in properly either. 1500-2000RPM for 1/2 an hour at first start up to ensure lifter rotation was the standard procedure when I raced.

I had lifter issues on small displacement OHV race engines quite a few years ago, as did other engine builders and everyone was quick to point the finger at the bottle of oil when the culprit was the lifters and to a lesser degree, cam lobes.
We ended up building a cam running in rig (old block electrically driven) so that the lifters and cam was bedded in before being slotted into the block.
Never had a an issue again, and we were running a variety of low viscosity synthetic fluids using different synthetic base chemistries. (di-ester, PAO and GrIII)
 
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