Educate me

[Spaceace]

Just for s & g's I stuck my finger in the oil fill hole while doing a LOF. What I thought I felt was a rocker arm.



What was it?



It was loose as hell. If it is a rocker, why with solid lifters would it need to be loose at any part of the cam rotation.



See that's what I get for putting my fingers where they do not belong.

 

[GBerry]

rocker arm

howdy Spaceace

dont know if that is a rocker arm i havent had the valve cover off a cummins before and dont know if the cummins has solid lifter cam but all solid lifters and hydraulic lifer cams even roller cams have a small amount of valve lash or clearance so that when the engine starts warming up and the valves and the other metals start to expand and grow in length the lifters and the rocker arm fulcrums wont be so tight that the oil layer is too thin to lubracate and the metal surfaces and gall !! that is what usually starts a cam to go flat

not the answer your looking for maybe but the best I got

Guy

 

[Floor It]

What you felt was a rocker arm, it will be loose during what is called over-lap. Its probably not as loose as it seemed,there should not be hardly any movement in the direction from push rod to valve tip-but there is alot of movement from side to side,it will roll from side to side on the fulcrum ball, oh yeah its a solid lifter cam. Hope this answers your question

 

[boonsur]

You should feel some "slop" when the lifter is not in the profile of the cam.



A "mechanical" lifter actually disengages the lobe on the heel (base circle). (side note, the lobe does not have to be hardened all around like a hydraulic lifter does). You can quickly tell which follower a cam is designed for, by looking at the lift profile. A hydraulic profile will remain at zero lift (plus/minus a little runout, etc. ), then get right to business. A mechanical cam will slowly ramp up to "engage" the lifter, then kick into the rise. This is why valve lash is important. Too little, the will be no room for things to expand when warmed up, but too much and the slop will not be properly taken out before opening the valve.





ps. I spent 13 years of my engineering career working for camshaft manufacturers (We made all of the cams that Cummins uses).