Originally Posted By: turtlevette
Originally Posted By: OVERKILL
Originally Posted By: turtlevette
Now. I wonder. How much sliding do roller lifters do. There has to be some.
How much sliding do the needle bearings within the roller lifter do? I would think ep and anti wear additives are still important in a roller cam system.
AW? Sure, EP? I don't think so, since most oils aren't dosed like a gear lube. I've handled a good number of high mileage roller lifters and none of them have had any real wear in the roller area, nor did they have play that would indicate wear in the needles. These were OEM Ford roller lifters from SBF's for the most part run on typical PCMO's.
I think you'd be more likely to see sliding in valvetrains with marginal spring pressure where you are near-float and the roller skids across the lobe face rather than rolling, which it would otherwise do with sufficient pressure on it.
I wonder how much study has been done on roller valve trains. I would think they would Normally be in hydrodynamic mode so you have no metal to metal contact. You have the fluid friction which would turn the roller, but I seriously doubt the speed is equal to the cam speed.
I'm going to disagree and say high performance valve trains with lots of spring pressure would benefit from ep type additives which would be needed on the ramp when you lose hydrodynamic lubrication.
You are welcome to disagree, I'm simply stating my experience with what is being discussed. From what I've seen in the SBF scene, back when I was more actively engaged, oil was not a concern in camshaft/lifter wear with roller engines. It was far more about keeping the bearings separated and so the focus was more on necessary viscosity. I don't remember any of the guys with high revving high spring pressure roller setups ever being worried, nor do I recall any failures that were of that nature. You'd see the odd dogbone failure with the factory setup and then the lifter going sideways and wiping itself and the lobe out, and we saw some of the less expensive rollers fail with the pin coming out of them. But the OEM Ford lifters and the high quality aftermarket link-bar offerings, this was never an issue.
I'm sure there was quite a bit of study work done on the development of roller valve trains, most of it in the 70's and 80's when they were working on making them mainstream.
If there was a need for EP additives in PCMO's to protect roller valvetrains, I'm sure there would be evidence demonstrating that. From what I've seen, there isn't, and the primary draw of roller valvetrains in high performance builds is the ability to run a more aggressive lobe profile while maintaining streetability and durability. I've built a few reasonably high revving 302's with both stock and link-bar roller lifters with the necessary springs to support 7K operation and it is the springs that give out and need to be replaced when these are used as street mills. Tear-down has never shown camshaft or lifter wear issues when high quality parts are used.
I simply don't see evidence of the scenario you are alluding to being benefited by the inclusion of EP additives actually existing. That may be because the AW additives like ZDDP are sufficient at that interface and thus, EP additives, like what one would see in a gear lube or grease, are simply unnecessary as the forces experienced, even with elevated spring pressures on the narrow roller/lobe interface, are not sufficient to warrant it
