Just came across a YouTube video on lifter modifications from Delta Cams. Makes sense to me maybe this is the key to eliminating and or greatly reducing cam/lifter failures. Dan
So, in a nutshell, he’s increasing leakage past the lifters to get more oil to the lobes. Have we been responsible for destroying cams ourselves, by trying to restrict top end oiling and the subsequent drain back of oil to the pan so much that we have limited the splash oiling of the cam and lifters? Maybe a worn older block isn’t such a bad thing after all…
I have a set of Johnson solid lifters that had a tiny hole on the face of the tappet that would accomplish the same thing. Yes, the new stuff needs all the help it can get.
The hole in the face is counterproductive. We tried that on a Diesel back in the 1970s. It didn’t work. We then looked at the tribology at the interface of the lobe and lifter face. The rotation of the cam against the lifter creates a hydrodynamic wedge, and the pressure in this hydrodynamic wedge is in the tens of thousands of psi. (Look up hydraulic wedge). The hole actually flows backwards, up into the lifter instead of to the cam interface when the engine is running. We ended up putting a lifter with a silicon carbide face into production for that engine to solve the spalling issue. Subsequent engines were developed with roller followers instead of flat tappets. The rollers let us run higher valve acceleration rates for better performance without violating surface stress design criteria (hertz stress) at the interface.
I bought the Crower version with the tiny slot down one side to go with the Comp Cam in my new 389 Pontiac. I think the Crower slot goes all the way down. I kinda like that their little flat stops short of the cam wear surface. Either way it seems like a long overdue improvement.
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