So I've acquired a second old D4 recently and of course the pony has carb issues. Now, I work as a mechanic for the municipality and the other day a certain machine came into the shop. It is used in ice arenas and has a 10.5 Briggs and Stratton engine on propane which got me to thinking hmm what would an old Cat pony be like on propane? No gumming up carb from infrequent use, no rusty fuel tank blues, no diluting the crankcase oil and wiping out the bearings...hmm. I'd be curious to try although I'm sure it would be a fair bit of work to make it run right. I just like scheming and dreaming...trying new things. Any thoughts?

I believe Steve over in Michigan has some sort of Adapter System to test run Gas CATs on Propane? I thought he posted about it once?

Is there an Evaporator on that system? Or does it use Vapor Draw?

-i had a 86 Chev pickup on propane for years and it was trouble free....except it was hard on cylinder heads (valves)

-i would say it's definitely doable...but would I....no...not when a little maintenance on the pony is so easy..

A little Impco 50 cfm carb.
vacuum lock off though you could do without that
a regulator/vaporizer if you’re in a cold climate and will operate in the winter.
Some AN fittings and hose ends
Good to go
It would be a little tough to hide the propane bottle away anywhere, you would probably wind up with it sitting on the fender.
Friend of mine used to have a Ditch Witch trencher that he had running on propane vapor. I think it had a big Kohler or maybe a Wisconsin and it would ice up a grill bottle when you were digging pretty hard.

I’ve got several vehicles running on propane and it’s great but where to put the tank is sometimes a compromise. Sometimes it’s easy like hanging it under a flat bed on a pickup and sometimes you really don’t want to loose the space like in the bed of a regular pickup but it’s got to go somewhere.

A pony motor would never rack up enough hours to affect the valves. I pulled the heads off my 93 Chevrolet last year expecting they would be worn up into the head really bad but they weren’t. Still needed a valve job but maybe it’s to be expected with something that old. It did have a couple dead cylinders that I was attributing to burned valves but they really didn’t look like I was expecting. The shop that did the work said the heads looked pretty good, and it didn’t need any valves or seats. Like I said, I was surprised.

I've always been impressed by propane and natural gas. They run clean and the oil stays clean. My dad had an 88 F350 with a 460 on propane. It had 425,000 hard km and never skipped a beat. I suppose it shouldn't be too hard to keep a gasoline fueled pony kept up but I would enjoy the challenge of rigging a pony of run proper on propane and enjoyment is what these old gals are about to me! I dont have much knowledge of propane systems so I would enjoy the learning aspect too!

i have been around propane and butane all my life. many combines and tractors,trucks,pickups irrigation engines and you name it on propane. i have a 2013 ford f350 on CNG.

The IMPCO carburetor I mentioned is a reliable way to go and they have a lot of adapters etc to make their carbs fit just about anything, but another way that might work well enough is to convert the existing Zenith cast iron throttle body by installing a “spud” into the carburetor throat through the area where the bowl attaches. Probably can JB weld or drive a tube through the center hole where that long jet comes through. Might be a little small, I can’t remember how big the hole in the throttle body is.

Spud type mixers are pretty simple but rely on the size and position of the tube opening in the carburetor Venturi for proper metering. Usually you’ll have a “load” valve on the connection to the spud to tune the mixture.

"Neil" wrote:

Or you could go high-tech and put injectors on it - course then you'd need some unreliable electronics and a bunch of other expensive junk to make it work : )

that's a good one Neil, a real knee slapper, where is that emoji:spy: so true..