If you are rebuilding the Engine in your car or truck one of your many considerations is the camshaft. Should you replace it or is it still good enough to use? Camshafts are a lot more complex than many of us realize. For one thing the top of the camshaft lobes are not flat across the top, Rather they are tapered so that it will cause the lifters in the engine block to rotate. If they are not allowed to rotate freely... without that taper the camshaft will go completely flat in minutes. Notice that I didn't say "COULD GO FLAT" I said "WILL GO FLAT"
So obviously this is a important thing to consider. When the cam goes flat all those metal shavings will be circulated all through the engine and it will have to be torn down and inspected. Especially the bearings It is easily checked however and fairly easily corrected when caught soon enough.
Along with the Cam lobes being tapered the lifters have a crown on them. the center line on the cam lobe and the lifter is offset slightly so that the lifter and the cam align in such a way that causes the lifter and push rods to spin slowly while the engine is running. In fact if your engine is running you can remove the valve cover (OHV) then wipe the push rods on one side and run a felt marker up and down the push rod (you are only removing oil from the push rod so that the marker will show) After you have marked them. start the engine with valve cover still off and watch the felt lines. If the camshaft and lifters are all rotating then your cam is probably good. I say probably because that test Only tells us that it's good for the moment but a through inspection will be needed after the tear down. (keep lifters and push rods together and numbered so that they can be installed in the same location upon reassembly).
Inspecting the lifters will tell you the health of the camshaft. If ANY lifters are bad then so is the cam. To check the lifters wipe off the oil from one lifter and place the side on the crown of another and see where the daylight shows through.. If there is daylight in the center that lifter it is definitely gone, no good, kaput! They should rock slightly from side to side so that daylight shows at the sides. If the lifter face appears to be flat it is also no good, If ANY of the lifters are bad then ALL of them should be replaced, as well as the camshaft because some used and some new lifters on a new camshaft will lead to an early failure. The camshaft is the cause of many problems and should be replaced if any problems exist, the cam is in the very center of the engine and is not easily replaced, so while you have the opportunity it's better to spend an extra couple of bucks now than to spend a lot more money later replacing Main bearings and rod bearings and even camshaft bearings later.
There is a surface treatment that is done to all cast iron camshafts. It is a phosphate coating that inhibits rusting on the lobe areas and helps retain pre-lube during the break in procedure. It looks a lot like graphite spray except it's embedded into the surface of the cam.
The bottom line is that when it's time to rebuild your engine the camshaft should be replaced by either a reground camshaft or new one if available.