The CVH engine uses very large valves as standard. Significant power can be extracted without changing the valves. The problem with the large valves, is that they are heavy and have a tendency to drop the exhaust heads. The std valves are more reliable, particualry if you use early sodium filled.

My engine saw 7400 frequently, at over 2 bar of boost. I dropped a valve before christrmas and it ruined the engine - the exhaust valves were ceramic coated too, as i new this was in issue. This was after around 40k, the rest of the engine looked like new. I'm using a 16v engine now, as the valves are much lighter. But, if i was to do a CVH again, i would have some custom valves made up in a much stronger material, although it's costly.

Rick.