Valve closing clearance question/discussion
This is purposely sort of a troll post, but I'm trying to bring out the technical minds to discuss this.
The simple question:
What is the danger in having valve closing clearances on a desmodromic engine that are too tight?
Some points I thought up, but I can't make them all work together:
o What is the thermal growth difference between the valve itself (steel) and the distance between the valve seat and the cam (aluminum)? (does it matter for closing clearance since the closing rocker isn't directly above the valve as far as actuation? maybe it matters only for opening clearance?)
o What is the thermal growth (thickness) of the rocker? (does it matter?)
o Why is it that on some engines the spec is close to zero, and on some it's much higher, up to maybe .008" at the high side of the tolerance?
In my pea shaped brain, it seems to me that the half rings and valves would be much happier with less closing clearance, the least possible, to prevent thrashing of those half rings. Maybe this is an overly simplistic view?
|