Very Agressive Profilef Camshaft Break In 2

[patprimmer]

I have been asked to advise oil or oil additive selection to improve break in performance for cam and flat tappets.

The engine is being built for an engine performance competition conducted on a dyno.

The competition calls for best average power over an rpm range of 2500 to 6500, so it needs a very wide power band as well as high maximum power. It is restricted to a traditional American 8 with push rods and flat tappet design.

One avenue being tested is to use a very high lift but fairly short duration cam. The limitation is cam lobe break in. If they survive 30 min, they generally last long enough to complete the competition.

We suspect an oil with high phosphorus or sulphur for break in will help. As far as I know, no engine oil with high sulphur AW or EP additive is available, but high phosphorous engine oils are

My inclination is toward a diesel truck engine oil, or a polyolefin based racing oil like Redline.

I would like some advice from someone who knows rather than my guessing. I am very much hoping DRWebb comments with advice based on real data.

If we need to break the cam and rings in on different oils that could be done by using a stock cam while the rings are being bedded in, the change cam, followers and oil. Run 20 at 3000 rpm min on weak springs, add stronger springs run another 10 or 20 min at 3000 rpm.

If it meant getting a cam with an even more aggressive profile to live, we might break in the cam in the engine with no crank, rods or pistons, just valve train, driven by an external motor and supplied with hypoid oil from a external source.

Then reassemble and go to very light weight race oil for the competition

My thoughts are to try to obtain about 1% ZDDP total in the oil if we use the diesel truck oil route, but once again this is a guess.

How do I get maximum film strength and anti wear and anti scuff for short term.

Things like anti foam, low ash, high TBN, viscosity, anti oxidant or detergent properties are of little concern vs film strength and AW or EP





Regards

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[swall]

Are the cam and tappets just bare steel or are they coated some sort of phosphate and dry film lube?

 

[evelrod]

Hi Pat. I can't help with your problem other than anecdotal... our last engine, a 189hp., 1594cc DOHC Lotus engine last week. Three days on the dyno ...lot of work but no break in problems this time (have had problems in the past). I used Castrol 20W-50 for initial break in using an old set of Cosworth L-1's then on the second day switched to the very aggressive rate 280 @ .050" billet cams using a tube of Isky lube for assembly and Redline 40 racing for tests.

I know this is not what you are looking for, but I just thought I'd throw it in as it is what I have done for many years, mostly with good results.

I'm interested to see what gets posted as, I too, am always looking for methods better than my own. Especially considering the ongoing changes in production engine oils.

Rod

 

[romke]

i am not sure whether you can talk about break in in this case, like in the sense you would talk about break in with pistonrings on liners. in the latter situation a copious amount of oil to take away the heat and the "grinded down" debris that result from the break in together with some antiwear additive usually does the trick.

in the case of a camshaft and tappets, the situation is quite different. since you have contraform contacts here, you will at best get elasto-hydrodynamic lubrication, with very high contact pressures and occasionally mixed or boundary lubrication where the antiwear additive has to safeguard cam and tappet for cathostrophic wear. in fact the situation between cam and tappet can be likened to the breaking in of machined gears - you want the surface roughness to diminish so that a bigger contact area is formed to reduce the load.

there are thus two things that could be done. first try to grind down the asperities under low load - a rather thin oil with sufficient antiwear properties could work here. running the engine at say 1500 rpm for a couple of hours with a SAE 20 API CF classification oil could be used for this. this proces is the first step to obtain the largest possible contact area. with automotive gearboxes i have in the past used diesel fuel for this, but for obvious reasons this no option in a firing engine, even when only idling.

after completion of this step you should end up with as good as possible mating surfaces.

as a second step i would then apply a socalled "lubricating varnish", a solid lubricant like MoS2 that is dispersed in a suitable carrier so that it can be brushed on the surfaces to be coated. you would have to follow the instructions of the product quite closely, since these substances are best used on bare metal, where most metals are coated with some kind of oxide layer. you thus may have to clean he surfaces with some kind of agressive fluid.

step 3: fill the engine with an engine oil that both contains a lot of antiwear agent (API SG or SH) with both a high viscosity index and a high pressure/viscosity coefficient. the latter is important because oils of the same weight (SAE number) will behave quite differently in this respect. be aware that standard viscosity tests do not sufficiently show the differences when under high load - and you will need all the thickening under pressure you can get. Most synthetic PAO-based lubricants are better in this respect then engine oils based on API Group I, II or III baseoils.

I would go for a rather thin oil 5W-3 or so. When under high pressure (and pressures between cam and tappet may go up to > 5000 bar) there is not much sense in using a thicker oil, since the actual viscosity is more or less the result of thickening under pressure, whereas on the other hand a thin oil would help to carry more heat away.

what classification the oil has is of less importance, although you may be right that a diesel engine oil would incorporate more antiwear.

i would not go for an oil with an antiwear agent based on S and P, since these EP types of additives depend on rather high flash temperatures to become active and those temperatures might not be reached in the contact zone. I thus would stay away from a gear oil type of lubricant and opt for a normal engine oil where the antiwear properties are based on Zn and P compounds that get active at lower temperatures.

 

[patprimmer]

Swall

First off they are cast iron.

They will be coated with what the cam grinder thins is state of the art. Parkerising is a term hat comes to mind. It gives a very dark grey mottled finish. We could coat with anyhing that might help.

2 hours life would be adequate.

Rod

Your exact process with either Redline's best recommendation and molly assembly lube or Rotella and molly assembly lube was my first reaction, then I wondered if I was out of date or if there was something better.

Regards

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[swall]

Pat--the "dry film lubes" I mentioned basically start out with a manganese phosphate base (aka Parkerizing) and are given an impregnation with a variety of lubricants, including moly. Some also use a baked polymer film to retain the lube for long term durability. That would be overkill for a break in application and you could probably do just as well with the phosphate base and a thick moly type lube. So no, you are not out of date. Moly hasn't changed, phosphate hasn't changed, but the carrier lubes have, for the better. One of my colleagues is a recent hiree from Crane. I will try to touch base with him tomorrow and see what he suggests.

 

[evelrod]

Pat, I have limited experience with American V-8's these days, but I looked into some of my old mags and found an old Isky catalog. In it there was a recommendation for run in using their assembly lube and reduced valve spring load for initial break in. This is from the 60's so it may have no relevance today. Apparently that's what was done "back in the day".

On my "single stick" engines, I just run in everything at the same time. No special anything for camshaft/lifter except not to let it idle much in the first startup.

Rod

 

[swall]

My ex-crane colleague felt that the Crane #99008-1 lube was the best, with Moly paste being second choice. The latter has a tendancy to plug the oil filter.

 

[Tmoose]

Lower tension break-in springs were popular once upon a time for maximum effort flat tappets.

The late (in)famous East Coast cam grinder Domenic Ravesi used to recommend hand polishing tappet faces. Kind of makes sense, except if it might change the giant radius sometimes provided to ensure tappet rotation, or inhibit slight plateau finish with oil pockets.

 

[drwebb]

I don't have a lot of specific break-in lube data to draw on, but here's some thoughts to spur your thinking.

Don't get carried away by excessive top treats of ZDDP. Formulators who have worked with this stuff know that it saturates at pretty low levels in standard wear tests, so more doesn't reduce short-term wear. (On the other hand, marketers who work with the stuff have their own objectives . . .) If regular motor oil isn't enough ZDDP then you need different chemistry. MoS2 greases are often used for assembly lube for reasons mentioned by others. There are some engine oils available that include EP fortifiers- look for racing or motorcycle oils that tout their transmission protecting properties.

If these cams are really operating in the extreme regime then it may be helpful to try and identify the failure mode. For example, micropitting can be initiated by particles in the oil, in which case opening the motor to install progressively heavier springs could increase the chance of imminent failure. Also, some chemistries can harden the surfaces excessively and promote cracks that lead to pitting, while others may allow some wear but move only gradually toward failure.

I would recommend as a first stroke to pay extra attention to cleanliness on assembly and use a high quality/high solids MoS2 assembly lube maybe coupled with an EP-fortified oil and see where to go from there.

 

[patprimmer]

dr and Rod.

Thanks. What you both say pretty much confirms what I thought.

The engine will be assembled with surgical level cleanliness.

Oil and filter change interval will be minutes, not hours of running.

I didn't consider the oils specifically formulated for running the engine and gearbox in the same oil and that is a very worthwhile thought.

swall

I am interested to find out more about Cranes assembly lube vs molly paste types as filter clogging is a minor concern that I would normally address by very careful application of the paste an using large or dual in parallel filters.

I am inclined to break the engine in with stock cam and a very light synthetic car engine oil, then change cams and run a motorcycle combined engine/gearbox oil during the cam break in procedure.

I am thinking the motor cycle oil might be best for the competition as well



Regards

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[romke]

using a motorcycle oil is indeed an option. however, the difference between a motorcycle oil and a car engine oil is not in the capability of gear anti wear protection, but more in some extra testing to make sure that oil immersed clutches behave as they should, without excessive slip as might occur with some "car only" engine oils. apart from that: a lot of socalled "motorcycle oils" are identical to car engine oils - the difference being only marketing.

as far as zinc content is concerned, as long as you stay away from the latest generation of "lowSAPS" oil, there will not be a problem. even those lowSAPS oils have to meet stringent antiwear requirements - and they do.

 

[evelrod]

Pat, romke is spot on about the "marketing" aspects of so called "motorcycle oil". Granted, several mfgrs. make specific oils for motorcycle racing, Mobil 1 comes to mind, but VERY expensive and hard to come by. I've been using Redline in my Mini (MUCH more difficult on lubrication than ANY motorcycle) for several years now with good results.

As to using moly assembly lubes...Well, I used them for...longer than I care to remember. What I am using now is a synthetic blend assembly lube and Mobil 1 or Redline synthetic wheel bearing grease...I've kinda gotten away from using moly on everything...However, in all the years I used it exclusively for EVERYTHING, I never "clogged a filter" or had any other adverse problems. I did try the Texaco 'graphite' crap once...What a joke. That crap leaked where I did not even have leaks...plus it did clog a std. filter. Never tried it on a race car, thank goodness!

Rod

 

[patprimmer]

Rod

I expected the Mini gearbox would be very demanding on oil.

I normally use Castrol molly grease designed for CV joints or cam lobes only.

I never had a problem, but on this engine we want to really push the envelope on cam lift rate as I think getting it right is the difference between winning and DNFing.

Last year, the guy who did best in the eliminations, lost a lobe in the finals

Regards

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[swall]

One characteristic of "motorcycle oil" has to do with unit engine/transmission configurarations commonly employed (engine and transmission share oil). The oil is designed to resist the shear of the transmission gears. As I understand it, the shear breaks down the long molecule chanins in the oil and thus degrades it. So, motorycle oil would not necessarily be any better in an extreme EP application like a camshaft.

 

[drwebb]

"the difference between a motorcycle oil and a car engine oil is not in the capability of gear anti wear protection, but more in some extra testing to make sure that oil immersed clutches behave as they should"

Well I don't have data on break in oils but I have reviewed a lot for MC oils and this claim is a gross over-generalization, which can be verified by performance and/or chemical testing. I'm not going to make this a commercial forum by recommending particular brands, but look for products claiming enhanced gear protection (not just clutch capability, or shear stability which have no bearing on the current application).

Also, surgical cleanliness doesn't help if the oil you put in has any swarf- as some out-of-the-bottle lubes may. For break-in it might be worthwhile to run it through a 10 micron filter if you want added security.

 

[swall]

My colleague's prefence for the Crane 99008 lube is largely anecdotal. He reports having used it on 2500 cam installations and having great sucess with it, never having lost a cam while using it.

 

[patprimmer]

OK

I never lost a lobe before either by the molly grease and fast idle light springs method, but for this project we are tempted to get a cam ground that would be to aggressive for this method if we feel we can get a better process. That is the point of the research.

I will suggest getting a marginally safe cam and two extra aggressive cams. If one stands testing run the other in the contest. If it fails in testing, run the safer cam in the contest.



Regards

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[evelrod]

Pat, if $$$ is no object, grind on a EN-40 billet and have it nitrided to about 80 and pray for the lifters! ;-)

Rod

 

[patprimmer]

I wouldn't have to worry if the lifters had hardened steel rollers on them, but I guess they would notice. ;-)

Regards

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