DubTrub, nope, it's a Lycoming IO-320.
Carb ice did occur, but the increase in RPM is instantaneous when I pull the knob out : unless ice can melt incredibly quickly I suspect something else must be going on.
However, you're all quite right, I always run the engine for a while before I do the run ups, so I guess it's a possibility.
Thanks all for the answers.
What do you think, Capn H ?
FF
