I may have misunderstood, I thought the pitting was caused by rust, inconel is very hard. Any clue what brand they are ?

Don't know what brand. I double checked with a magnet and the stem is magnetic but not the head, maybe cheap brand of inconel?

Might be time for a new set of good valves.

I just checked one of the good exhaust with a magnet and it's only magnetic at the top where the keeper go's. What do you think of that?

I would call Ferrea or Manley or both and ask a tech for their opinion of what's best for your application.

I was able to find the manuf. marking on the top by the keeper with a magnifying glass and it's a REV CL-1717 inconel. Seems to check out as the same type of valves and not cheap. Why would the valve that's bad with the pitting be magnetic on the stem and the valve that's good be magnetic only at the top by the keeper? Does anyone know?

Personally, you have enough evidence there to assume you will have issues with any other valves your mechanic replaced. I would at this point do some cheap insurance and replace all the valves with Manley or Ferrera or other good valve. You have the motor apart and the extra $500 at this point will save you headache. Last thing is you need is a valve hanging up and breaking a tip on you. Just my .02

If the stem is magnetic and the head is not, it's a 2 piece valve. The head is Inconel and the stem is SS. The stock valves in a 454/502 Mag, for example, are the same way. Better quality valves are solid Inconel, like Manley's. If you have one that is only magnetic on top of the stem, then it is all Inconel. That is a quality valve. I would change them.
Eddie

I understand about the inconel head with stainless stem. The valves are manuf. by REV. The issue here is that two valvs from the same manuf. that have the same item no. REV CL-1717 are different! The one that is damaged (see photo and read post #31) has a magnetic stem and all others with non magnetic stems are good. QUESTIONS: Did the manuf. mix up the item numbers? Could the stem become manetic and get pitted from heat or friction? Was theis valve under oiled? Is somthing wrong with the guide?

I would say that it became pitted because it is only SS, not Inconel. If it's magnetic, it's not solid Inconel. I would guess that it must have gotten water on it at some point to cause the pitting. It was probably from reversion when the valve was hanging up in the guide. Personally, I wouldn't chance it and would replace all of the exhaust valves. I'm not familiar with Rev's valves. I've never used them. A set of Manley's will only run you about $425 or so. That's cheap insurance to know that they are good.
Eddie