Forgive me,
I misread that the engine was in the heli, and the heli was strapped to to the work bench. I originally thought you just had the engine on a test bench - sorry.
So cooling would not have been an issue, but with no load, the engine would over speed and not get up to correct running temp. So you must put the rotor and tail rotor blades on to make the adjustments.
I actually do something kind of dangerous when I am setting up a nitro engine on a heli, but it works and rarely do I have to mess around with things at the field after words.
I clamp the bird onto a Work-Mate bench and then crawl under the heli and perform all engine adjustments (low, mid, and high) while the bird is running. As long as you have a good way to clamp it down and make 100% sure you don't lift your head up, this is a very quick way of setting all carb adjustments to get everything almost perfect for your first flight in less than one tank of fuel usually.
If you do try this, be very-vary careful. Wear impact goggles, ear plugs, and even a helmet just in case. Keep your hands low and away from the main gear or fan. After making the adjustment, throttle down to idle and crawl back out from under the heli and then recheck the engine transitions etc. You will get nitro oil mist on you and your radio, so spend as little time under the heli as possible. It is not a nice environment under there.
Just a thought - The last thing I want is for someone to loose their head over this method - literally!
H.H.
www.rchelicopterfun.com