My Roush 427 SR was using quite a bit of
oil at 8k. 11k pulled the heads and sent them out. Builder called me, and showed me the valve stems. The bronze valve guides actually wore depressions in the valve stems, allowing
oil to flow into the combustion chambers. It was his opinion that the valves were cheap Chinese valves with a substandard manufacturing process. Replaced the valves the engine ran fine. Have a couple of friends, one on here, who had the same engine. It turned into a disaster for him. If he so desires, he can comment on his problems. Decided to get rid of the engine before it became a boat anchor, sold it and bout the KC 482. Great decision as far as I'm concerned.
Some seem to have engines that have done quite well. I can only speak from my personal experience.