Bruce,


Since at full throttle, with a properly adjusted high speed needle, the con-rod is always in compression, it cannot make any noise; even if it is loose on the crank-pin, or on the wrist-pin.

For a sport .75-.78, that actually has its horsepower peak around 13K RPM, an 11x8 is too small a prop.

It does make a higher pitched sound, that with the reduced power output, is no more than a shrill scream...

Prop it where the meat of the power curve is, around 11,500-12,000 on the ground, so unloading in the air, it will really give you good thrust and power.

I think a 12x8 prop will be more appropriate.


That noise you are hearing could be detonation! Try to richen it a little and see if it changes/goes away.