Quote:
Originally Posted by Shazaam!
About 14 years ago, (Fast by) Ferracci came up with the following recommendations by taking a 4V head and turning the cams with an electric motor in the 10,000 rpm region and seeing what happened. He found that these clearances minimized issues with valve bounce and float. These numbers don't have anyting to do with running clearance or heat or anything, they're just what seemed to work the best mechanically.
Intake
Opener - 0.10mm
Closer - 0.10mm
Exhaust
Opener - 0.15mm
Closer - 0.10mm
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Do you know for what engine this is? It would have to be either air cooled or a Desmoquattro of course...
The reason I ask is because the length of the rocker must also play a role in this, depending on lift and acceleration rate of the cam.
I had a brief discussion about this with Kevin Cameron at the WSB race at Miller. He said that the Ducati engineers are aware the there is a spring effect of the steel rockers, and this does play a role with design of the engines, including the MotoGP engine.
With this much clearance, there must be something more going on that just minimizing clearance...