Cadillac Seville / Cadillac Eldorado Forum Discussion, Camshaft question in Past Cadillac Vehicle Discussion; Greets,
What exactly would be considered the "thrust portion" of a camshaft?
"thrust portion" on a cam is a new one on me. Flat tappet cams are ground either with the lobes slightly tapered: about .001" to .0015", or with the lobes slightly offset in relation to the lifter center so the lobe action turns the lifter (or cam follower) each open-close cycle. This evenly distributes wear over the face of the lifter, and is why a properly operating lifter shows a polished circular pattern on its face. This action tends to "walk" the cam forward against the timing chain/belt and timing cover. Several manufacturers make thrust buttons for cam ends, or the engine manufacturer builds-in thrust bearings or buttons as original equipment. Thrust bearings are a shoulder on one or more cam bearings while buttons go in the cam end, bear against the timing cover itself and are lubricated by chain splash.
So - the "thrust" portion of the cam would be the timing chain/gear/belt end of the cam. Obviously, roller cams are not ground as above because roller lifters or cam followers don't turn in their bores, so there's no tendency for the cam to "walk". In our case, 2000 and later Northstars have roller cams.