There seems to be differing views on what valves to use for a turbo CVH.
One school of thought is that OEM valves are perfectly fine for a turbo CVH - even one with double valvesprings and higher RPM use.

Others say that a one piece stainless valve is far more reliable - even though they require bronze valve guides for the softer stainless valve stems.

The only engine I have used factory valves in is a Porsche 911 3.2.

What is the opinion amongst the CVH experienced?

Cheers

 

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.

 

Thanks Rick,

I am having a cylinder head done up now, and was looking for advice on the valves I would or should use. The head has been flow tested with the
standard 42mm inlet valve and 180 cfm @ 28" has been reached with some port reshaping. I am not sure what the upper limit is for flow with the 42mm valve.

Cheers

Perry

 

have u enlaeged the ports, what about the valve throat/seat area?

 

The ports inlet has been opened up to the gasket size.
The valve seat and throat area also cleaned up and opened up a few mm's
Most work has been done on short side radius.
Head porter trying to keep port velocity high.