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Thiokol 3700 hydromaster

racer15

New member
Hey all, I just acquired a (new to me) Thiokol 3700 that will need a little TLC. I'm wondering if anyone here knows where I can obtain a set of manuals for one. Any help would be great. Thanks.
 

redsqwrl

Bronze Member
GOLD Site Supporter
I have a 3700 manual, I'm in 54913

make an offer..... I will dig into it to see if it a later or early manual.
 

Dr. Zaugg

New member
I most likely have a manual. I would need your serial number to give you the right one.
Those have lots of surprises in changes that are not recorded.
Paul
 

racer15

New member
Thanks for the responses guys, I forgot to write down the serial number.(dumb I know) I will remember to get it when I head back up which will be in a week or two. It seems to run just fine, Just needs a lot of TLC. I'm new to the snowcat world but we have a remote off grid cabin in the Sierras that we have used snowmobiles to get to in the past. The snowcat seems like a good fit. Thanks Again.
 

Dr. Zaugg

New member
Please note that the Allis-Chalmers engine will not start like a gasoline engine when at the cabin. I suggest a small generator powerful enough to run the block heater and you will be fine. ALSO, the maximum speed that engine likes is 2100 RPM. LMC ran it way higher which caused many engine failures. It likes to run between 1900 and 2100 RPM and will serve you very well if you keep within that range.
 

Snowtrac Nome

member formerly known as dds
GOLD Site Supporter
we ran the same A/C engines in 60 k generators for years in the military at 1800 rpm they will run for ever that way. the only down fall is the motor is kind of becoming a dinosaur like my 380 ford the ac motor does have the roosamaster injection pump in it and that will likely be your weak spot add a quart of 2 cycle oil to your #1 fuel and you can double the life of the pump.
 
I had a Thiokol 3700AC with the Allis Chalmers and it was one of the best diesels I have owned. As I recall the max torque output was at 1700 rpm with a redline at 2100rpm. The old timer I use to talk to at the then LMC factory (Ted?) told me to run it at 1700 and it would last forever, anything above that was just wasting fuel and taking life out of the engine. I looked at a newer DMC 3700AC that was up for auction once and it operated at a higher RPM according to the placards on the dash but I bet as the others have said, it shortened the life. Would't surprise me if the factory just turned up the juice a little to boast a higher HP number.

It was a great cat and the only downside I could think of is it was easy to over stroke the pumps if you were working it hard like cutting hard icy moguls while towing a drag. The central location of the cab plus the mechanical sticks made the operation buttery smooth compared to the brake type steering of my first cats. Certainly sold me on hydrostatics for the type of snowcatting I do.

I am sure I have an old copy of the manual in my files if no one else comes through for you.

Randy
 

Dr. Zaugg

New member
Ted Finchum was a wealth of information. I think I even still have his card in my desk.
He was right, there is as much power at 1700 as 1900. anything over that was a waste.
 
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