Cam shaft tolerances
 

Recently decided to measure the lobe lift on an installed cam.
I am using a magnetic stand and dial indicator directly on the lobes.
Specs are .316" on both intake and exhaust lobes.
Most lobes measured .316", but a couple measured .312".
What would be the tolerance in this situation?

I have to admit I generally do not check every cam lobe. When I make a random check while degreeing the cam, I find most camshafts measure +-.001 on lobe lift. This is using a dial indicator attached to a tool that fits in a lifter bore. Using a magnetic dial indicator make sure the plunger is straight up and down. Measuring at an angle will give you a little error. If you are actually -.004" at the lobe, that's .006" at the valve. Not great but in a street engine, I doubt it would ever be noticed.

That may not be a concern. It's with in spec for a factory grind. A close look at the wear pattern would be your next check. If the lobes have worn .004 they will not have a clean wear pattern at the top of the lobe. Compare the wear pattern to the lobes that check good. If it looks smudged the lobe is on its way out. You can also determine a lot by inspecting the bottom side of the lifters. Make sure they are convex. If the lifters on the lobes that are measuring short have signs of wear those lobes are going bad..... Assuming you have the used lifters.

I may have misunderstood the original post. I assumed he was measuring a NEW camshaft installed in the block, not the old one.

Maybe not.... I assumed it was a used cam because it was "installed" ..... I figured either way have the question covered and the answers maybe helpful to someone in the future.