Very Agressive Profilef Camshaft Break In
Very Agressive Profilef Camshaft Break In
(OP)
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
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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RE: Very Agressive Profilef Camshaft Break In
RE: Very Agressive Profilef Camshaft Break In
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
RE: Very Agressive Profilef Camshaft Break In
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.
RE: Very Agressive Profilef Camshaft Break In
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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RE: Very Agressive Profilef Camshaft Break In
RE: Very Agressive Profilef Camshaft Break In
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
RE: Very Agressive Profilef Camshaft Break In
RE: Very Agressive Profilef Camshaft Break In
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.
RE: Very Agressive Profilef Camshaft Break In
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.
RE: Very Agressive Profilef Camshaft Break In
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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RE: Very Agressive Profilef Camshaft Break In
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.
RE: Very Agressive Profilef Camshaft Break In
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
RE: Very Agressive Profilef Camshaft Break In
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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RE: Very Agressive Profilef Camshaft Break In
RE: Very Agressive Profilef Camshaft Break In
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.
RE: Very Agressive Profilef Camshaft Break In
RE: Very Agressive Profilef Camshaft Break In
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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RE: Very Agressive Profilef Camshaft Break In
Rod
RE: Very Agressive Profilef Camshaft Break In
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