Snowfire not recommended over 4000'!?

[Fairchild]

I was flipping through my new 79-83 JD Fine Tune manual and something has got me stumped. Snowfire's are not recommended over 4000'. Why would this be? The next page shows the settings for a Sprintfire at altitude. It shows the Sprint using a VM32 carb and the Snowfire using a VM30. Other than that and the Sprintfire being liquid cooled I don't know of any other major differences, especially one leading to a Snowfire not being recommended for above 4000'..... Good thing I don't have one as I live at 5600'! Any ideas out there, if you clutch and jet it, why cant a Snowfire go up in elevation? All other Deere manuals I have show altitude settings. I would think setting it up like a Sprintfire would be just fine.....

Ty

[rminier]

This is my guess.....At sea level, the atmospheric pressure is 14.7 psi. At 5000 ft. this drops to 12.23 psi.
That means the air is only 83 % as dense at 5000' versus sea level.
In essence, you are giving up 17 % of the cooling ability with a free air engine....quite a bit.
A fan cooled engine doesn't care quite so much as you move up to thinner air....and a liquid cooled engine doesn't care at all (as far as removing heat from the engine)....as long as you have coolant and the water pump is pumping..

[Fairchild]

Sounds very logical..... Although the Spitfire's have altitude adjustments, both for the Kohler and Kawasaki engines. So I'm still a bit stumped.....

[Fairchild]

I suppose by the time Snowfire's came around they had it figured out the F/A's didn't cool well at altitude and never recommended it again and never changed the literature for past F/A machines. Maybe someone else has more insight to this. Seems it would have been easier to just say it must be run at very cold temperatures when above 4000'.

[rminier]

Yeah...I can't see any reason you couldn't re-jet and re-clutch a free air sled to work at altitude.
Certainly running around at 0 degrees or 10 degrees F at 4 or 5000 feet would provide at least as much cooling, or more, as operating at sea level on a 30 degree day.
Perhaps JD became more warranty conscious about a free air sled being run at 30 degrees and at altitude.....you know there would be people running around on the remaining deep snow on a 40 degree spring day,...then wonder why there sled was losing power.

[Fairchild]

Very logical again Rick.......

Yeah I'm very aware of temps in the spring when the pass opens in late May! Plenty of snow but temps can easily go into the 50's at 10,000'.....