Clevite Tri-Armor bearings are moly/graphite coated in addition to being a tri-metal bearing. Is it realistic to assume that the coating will remain after just a few thousand miles? Am asking because the cost is far more for the coated tri-metal bearings over the non-coated tri-metal bearings. I understand that moly & graphite are excellent friction reducers, but, based on what I've seen w/ rod bearing wear, the loaded area may not be coated for more than a few thousand miles. So, is there a benefit to having the remaining bearing area coated? Then again, after particles begin to lodge into the bearing, the coated area will be further reduced.

Originally posted in the external engine section & got zero replies. So, thought it could be answered & commented on, in here. Thank-you

 

What is the intended use for the motor in question?

 

I talked to a rep from clevite once and they claimed the coating would stay. They also told me that the coating is really only intended for cars that do a lot of sitting around so that when all the oil film leaks out of the bearings the coating helps protect against dry starts.

Other than that I have no experience with them.

 

It's a street w/ a few road course sessions/year car; stored Winters. Am freshening an LS6 block. Has drilled lifter cups, to help return oil to the pan sooner & a pre-oiler, to help prevent oil starvation in long sweeping higher G corners. The road course driving is 20-30 minute sessions of mid to higher RPM driving (up to 6700 RPM). Has an oil cooler, as well. Road course oil temps usually don't get above 240*F w/ coolant temps @ 200* F or less. (4) qts 15W-50 & (4) qts 5W-30 used when on road course, w/(2) qts stored in pre-oiler & (6) qts in pan, .

 

Hello?

 

hi

this isn't experienced feedback and somebody correct me if i'm wrong,
but my understanding is if you have metal to metal contact, key word here being boundary layer lubrication, that is bad. You never want that. When that happens there is friction, heat, and wear. You could tout whatever reduced friction claims of moly, graphite, ptfe, and so on for whatever coating but that friction is far more than the friction from lubrication provided by a proper film of oil between two properly machined parts with keyword here being hydrodynamic lubrication.

so for a running engine I generally see no point in coated bearings, and it would take a lot for me to choose a coated bearing costing a lot more over a non-coated bearing, point being I don't see it being cost effective. And even if they cost the same I still don't see the benefit of a coated bearing. They may claim this and that (more horsepower and greater fuel economy) but tell me how and prove it, just don't claim it.
The bearing coating I think has no affect when proper lubrication is taking place. There is no coating on the other surface, the crank journal, nobody raises an eyebrow about that. Correct bearing clearance and shape, for the intended viscosity of oil being used and temperature the bearing and oil will see is what's important, and I think that is second to guaranteeing adequate lubrication at all times. Anything else is just a band aid. Maybe if a coating improves surface hardness of the bearing or makes for a smoother more polished bearing surface then I could see a benefit. You originally mentioned moly/graphite, those are a dry-film lubricant type and have no use under hydrodynamic lubrication, much like the Slick50 engine treatment scam.

 

^^^

Cool, thanks for the feedback.

What about using main bearings w/ a full oil groove instead of just a 1/2 or top oil groove? Seems to me like the full groove could reduce oil pressure & will reduce the bearing area below the crank. Realizing that there is oil between the crank & bearing, the groove is still there. So, is the bottom groove beneficial because it delivers more oil to under the crank or is it actually causing more trouble than it's worth by reducing the bearing surface directly below the crank & creating a larger void that may reduce overall pressure?

 

You absolutely are not wrong. A tribologist I know says that the ZDTP in at least one brand of oil should provide the appropriate boundary layer protection for at least 6 months.

The difference between Slick 50 and a coated bearing is that the filter won't remove the coating from the bearing like it will from from an entrained particulate, which is what Slick 50 is. The coating will remain, although its utility remains in question. If you had a bone dry bearing, there may be some utility to it, as there is not doubt that PTFE will reduce friction. The problem is making it stay where you put it.

I wouldn't consider graphite in any application after it almost put ARCO out of business.

The single most important characteristic in any lubrication system is to have the correct viscosity for the application.

 

Found a 3/4 oil groove bearing made by Federal Mogul (Speed Pro). I feel better about using this one. The area directly below the crank is solid, no groove. The grooves on the bottom bearing are just short runners on the sides (@ 180* or just below the horizon). They basically funnel oil to the under side of the bearing.

 

...& thank-you to everyone for the comments. The feedback is helpful & has led to me making the correct decision on engine bearings.