Hey felleas last year decided to run my 468 with out a PVC valve graemlins/clonk.gif ,put in two K+N breathers on baffled valve covers.Spring tune up time removed valve covers to adjusted valves Man you wont believe the muk that built up under the valve covers :eek: .I run Mobil 1 oil and have total seal rings,not even 3K miles with last years use.Moral of story run a PVC valve,will keep things clean.Quick note adjust your timeing and carb without PVC valve then reconnect Vaccum hose.