My point is, regardless of what the bushing material is, even if it has zero friction, the shear of the oil in such close tolerances could be sufficient to cause the roller to slide up the ramp, especially in high lift aggressive cams that most of us are running. There is so much side load on the roller and the roller contact area is so small compared to the bearing area that it may be easier for the roller to slide up the ramp than roll over it. My concern is mainly when the oil is cold. It would not be out of the ordinary for me to pull the boat out in 40 or 50 degree weather with water temps in the upper 30's or low 40's. My 20w50 Amsoil is going to be just a little thicker than when it hits 200+. If bushings are the best thing since sliced bread, why are engine builders going to needles on cams? Not to diverge, but my 14,000 rpm 2 cycles were all needles on everything, granted when they went, it was catastrophic.
If you are worried about the side loading on the lifter getting away from the 1960's technology of a stock base circle cam and stepping up to a larger base circle GREATLY reduces side loading. Larger diameter lifter/wheel combination is also a game changer. As far as I know isky is probably the oldest cam/ lifter company out there .if the are pushing bushings as opposed to needles I'm sure it's for a good reason. Keep in mind Isky isn't the manufacturer that originally produced the bushing lifter but they are definitely full tilt with the design now.
HaxbySpeed
12-09-2014 09:45 AM
Originally Posted by ThisIsLivin
(Post 4232155)
My point is, regardless of what the bushing material is, even if it has zero friction, the shear of the oil in such close tolerances could be sufficient to cause the roller to slide up the ramp, especially in high lift aggressive cams that most of us are running. There is so much side load on the roller and the roller contact area is so small compared to the bearing area that it may be easier for the roller to slide up the ramp than roll over it. My concern is mainly when the oil is cold. It would not be out of the ordinary for me to pull the boat out in 40 or 50 degree weather with water temps in the upper 30's or low 40's. My 20w50 Amsoil is going to be just a little thicker than when it hits 200+. If bushings are the best thing since sliced bread, why are engine builders going to needles on cams? Not to diverge, but my 14,000 rpm 2 cycles were all needles on everything, granted when they went, it was catastrophic.
If you think it would be difficult for the bushing to turn on the axle with cold oil, imagine how difficult it would be to get all those little needles turning in that same thick oil.. I can't imagine a scenario where there is so much friction between the cam lobe and the roller that it would actually wear on the cam before the roller would start turning. I will say, if you run your engine hard with cold oil, the lifters aren't the only things I would worry about damaging. Also, needle bearings for cams have come and gone. I would never use them for a marine endurance application.
