By Staff
1 / 3
2 / 3
4 HP header
3 / 3
4 HP header

R.D. #1, Box 224, Drums, Pennsylvania, 18222

I purchased this 8 HP Model U Thermoil engine in 1979 from the
son of the man that purchased it new from Sears, Roebuck in 1918?
They used it to run a small thresher and feed grinder till the
40’s.Then it sat for ten or more years and the son acquired it
and ran a coal cracker for about seven or eight years.

Everyone who used this engine tells about starting problems. The
instructions say: prime first, then set compression relief lever,
turn flywheels with crank nine or ten times, remove crank, close
compression relief valve and if the Lord is willing the engine will

But not every time! I am a light weight person and not too much
on muscle and this method won’t work for me. The person I
purchased from said they put gas in it (one day when their Dad
wasn’t home). Well, the engine started and ran away from the
governor and being young boys they were afraid of it and they ran
away! After getting their heads together, they used a clothes prop
and opened the compressor relief to stop!

After having this engine for one year I figured the best way was
to use a Pony motor. I used a 2 HP Briggs only to find out I would
need at least 4 HP to turn the Thermoil through compression.

I finally got a 4 HP header (hit and miss). This would surely
have enough power to complete 4 cycles of compression and start the

I made a slide table to tighten the belt so I could control the
Pony motor when the Thermoil started (see picture #2). I have my
hand on crank of slide table and the Thermoil just fired for the
first time (cloud of smoke). Now I will slack off header and the
Thermoil will run on it’s own power.

This works very well for me! The Thermoil runs very well but can
give problems starting. The header will crank the Thermoil for as
long as it takes and never complains as I would tire of cranking in
two or three times. The first time I started the Thermoil

I had it in my garage with doors open and it started! I had the
governor wide open and till I locked the header up and got the belt
off, the Thermoil was bouncing the back wheels of the cart 4 inches
off the garage floor! This, plus filling the garage with smoke so
quickly, I had a few exciting minutes until I got everything under

I like the Thermoil very much. After starting it will run at 300
RPM all day with no problems. It knocks and bangs and smells just
like a diesel. I have enclosed two pictures. Picture #1, I have my
hand on the compression lever and have just closed compression.
Picture #2, The Thermoil fired first and second time. I am locking
off the header so the Thermoil can take over.

I usually start the engine with no water in the hopper and after
it starts I add water intermittently. Once I filled the hopper with
cold water and tried to start it but it just wouldn’t start. My
friend said the header was turning it over too slow so he held up
governor of header and adjusted fuel. The Thermoil was now turning
over much faster but it still wouldn’t start. After a few turns
it blew out the head gasket!

Gas Engine Magazine
Gas Engine Magazine
Preserving the History of Internal Combustion Engines