First, aftermarket automotive cams are often coated by parkerizing which does two things. It helps protect the lobe surfaces from corrosion until it is run inside an engine and it helps hold the initial layer of lubricant on the lobes between assembly and startup. It is wiped off the points of lobe/follower contact nearly immediately upon running the engine. This coating will never be present on a used cam so it basically tells one nothing about the condition of a used cam.
Next, what I don't like in the pic is that the rust appears exactly where the cam lobe is under the highest pressure. It would indicate to me that some thin layer of metal has been removed by wear, exposing a surface more likely to rust than the adjacent areas of the lobe where this wear has not occurred(and thus are not rusting). Uniform rust on a lobe that is easily removed *may* be acceptable for use on the cheap, but rust only at peak lift of the lobe is not something I'd ever want to see on a cam that was going in but I understand building on the cheap.
It'll work for awhile, perhaps more. How's that for a useless answer? I'm not familiar with the spring pressures or the hardness of the lobe face vs the follower face on these engines but I'd not be surprised if putting this cam in with unmatched followers results in accelerated wear of both cam and followers. However, assuming bryanj is correct, I'd not be overly worried as a hardened follower should not suffer much at the hands of a non-hardened lobe. Don't expect top performance from such a cam.
Be sure to use plenty of zinc in the oil...hehe. Seriously, really.
Ken
