Rocker arm wear

Was bored the other night and yanked the valve covers just 'cause I haven't checked any of that stuff in a while. Everything still looks brand new except the #5 intake rocker which has quite a wear line to the right side of the valve tip. Planning to replace it before TWS but I'm looking for root cause theories....I have a couple but not confident in either. I've only ever seen this on blown motors that had debris floating around....never on a clean "healthy" motor. Not sure what to make of it but it looks suspicious....

http://i1041.photobucket.com/albums/.../RockerArm.jpg

That is usually caused by a missaligned rocker stand. It could be that the stand is machined slightly off or it might be a piece of trash caught under the stand. At any rate you may be ruining the valve stem as well because all the pressure is centered over one edge of the stem instead of across the whole thing. Unless you correct this you may have a catastrophic failure of the rocker/valve stem. Grab an inspection mirror and look at this before you disassemble it to see if there is assymmetric contact across the valve stem. If you can't see anything try using a feeler gauge. If you can slip even the thinnest gauge into one side of the stem (the side away from the wear mark) when there is slight preload on the rocker, then you have a problem. Remove the rocker and inspect the mounting surface for any foreign material that may have been under the stand. At a minimum, replace the rocker and stand assy.

You don't want to drop a valve... ask me how I know...

That's the weird thing - valve stem is perfect. The only wear on it is a tiny shiny spot dead center. You look at the valve stem and then at the rocker arm and would swear they've never come in contact with each other. Talked to my engine builder about it and he said he's seen it before and it's generally just variation in the hardening process for the roller tips. Sometimes you get one or two that weren't hardened properly or evenly and apparently this is what that looks like. He wasn't worried about it at all once he saw a pic of the valve stem but I replaced the rocker anyway. Also checked the pushrod and mounting stud - no issues with either...good and straight. Once I get everything else back together I'll run it in the garage for a while and see what the new rocker looks like afterward. Thanks for the input...