Alberto

iTrader: (14)

I could be wrong, but I recall a tuner telling me that higher boost, could cause the valves to float with stock valve springs, but also with higher rpm than stock. Of course he could have meant only a marginal amount in regards to the boost and really the rpm affect it more.

If Im off, hook me up! I apologize we all learn from time to time...

edit-I started doing reading, and the answers are very mixed. Many experiences with higher boost apps like DSM's (40+psi) encountering float at rpms they dont at lower boost, but also explanations that seem to agree with kartkid.

Any input from the more knowledgable would be good...

binder

iTrader: (8)

+1

the bike engines i built for a local race team aren't FI engines and we have had instances at valve float. The cams are spinning too high of an rpm for the spring rates and the spring doesn't have time to keep the tappets in contact with the cams. Basically the tappet is bouncing off the cams which causes the valves to "float" open and stay open.

These motors are turning 17k rpms but a lot of the valve float is noted on a bad downshift. Rev limiters only work when the ignition is going, so when you're on decel and drop down too hard in the gears the motor can actually be forced to rotate faster than the rev limiter and this is where we will experience valve float and then a valve into piston destruction.