Hurricane at high altitude

[aus3620]

S!

When flying the Hurricane at greater than 15000 ft I consistently blow the motor one way or another. You know the symptom, shaking and all that.
I have tried adjusting the mix, closing the radiator (try to increase engine heat), change pitch/revs but cannot find a solution.
Any clues appreciated.
thx

[Osprey]

CEM on? Watch your temperatures - don't let the water over 105 or the oil over 90.