I recently had the valve seats ground on my 799 heads and installed them. The motor ran great for about 30-40 minutes and then sounded like it started to knock. I brought it to my mechanic and he said it sounded like a top end knock (valve issue most likely). I took the heads back off and everything looked great except the top of the valve stems looked to be ground down a little bit from the rockers. I am running stock rockers with PRC dual golds and stock valves. Any ideas on what went wrong? I want to get the truck running again but I want to fix the problem before buying new valves and installing them just to have the same issue again. I am running a brand new ls6 cam with the appropriate pushrods (same pushrods that were on my last 5.3 with identical cam, I forget the length)

 

What do you mean? Someone ground the valve stem tips down or is the rocker gouging the valve stem tip? Pics?

 

The rockers sort of gouged the valve stems I guess. It looks like there is fresh machine marks on the tops of the valve stems but they are uneven and you can see on a couple of them that they aren't perfectly flat any more. I am out of town until next weekend so I can't really get pictures right now.

 

Soooo why did the machine shop cut the valve stems down? Did they booger up the valve job so bad they're trying to hide their mistakes?