1984 triple e gmc gas/propane powered motorhome

I bought a Chevy truck from a friend that ran a gas co. it ran on either LP or Gasoline, I eventually done away with the LP because of the price and low gas mileage and running around with a bomb behind my head. One of his workers went on vacation and pulled a LP gas trailer behind his truck and would re-fill his truck when needed. as stated it takes a big hit on mileage and price. I had to start mine on gas and flip the lever on the dash to changeto LP when it started

One of the guys I hunt with also owns the local propane dealership and all his gasoline vehicles are converted to run on propane, all late model gas trucks. I know he starts the engines on gasoline and then switches to propane.

If I owned a propane supply company, I'd do the same. heck of a lot cheaper running propane when you own the propane company...........

I also know there is an outfit here in Michigan that stocks the parts and everything needed for the conversions and if you want, I can ask him.

I had a 81 GMC Midas with dual fuel. Sorry there is no such thing as a manual for such a configuration. There was a switch to change from gas to propane. As long as the propane tanks were turned on, that was all that was needed to change modes. There was a little chugging for a second or two when changing modes with the engine running. It was best to change after the engine was started. Trying to change when the motor was off would cause a week battery to go flat. A problem I had was that I had to change O rings in the propane system. After that, the system seemed to work well.

Propane had less power, and did not get as good miles per gallon. But back then, propane was much cheaper than gasoline. As I remember, I got 8 miles per gallon on gasoline and 6 on propane. I changed the exhaust to dual pipes and was thrilled to get one more mile to gallon. Good luck with your rig.

it was either special order
or the the original first owner had the conversion installed

i would start with looking under the hood for any NAMES i could find
then i would also search the web for LP conversions on trucks and vans
LP used to be a lot cheaper than it is now
its only upside is cleaner burning in the engine
the tank is heavy and the fuel has less BTUs of energy per gallon than gasoline

Dual fuel motors perform less satisfactorily on LPG than they do on straight LPG using an IMCO 425 carburetor. My 1990s toad was 100% propane. Two 83 gallon stacked motor fuel tanks behind the cab on a flat bed.

The engine was a blueprinted 350 engine with four bolt main bearings. Elaborate preparation was made for propane use. 12.5 to 1 Venolia pistons, Corvette cylinder heads with 2.02" intake valves a Bruce Crower roller camshaft, Corvette intake manifold and the Imco 425 carburetor. The compression ratio alone prevented any thought of using gasoline.

The end result was an engine that provided almost as much power as a standard factory 275 horsepower 350 engine does on gasoline. The vehicle spent it's entire life south of the border in areas that had 78 octane Nova gasoline.

LPG makes the engine run considerably hotter, and leaks oil through engine gaskets much easier. Why I do not know but it proved to be fact in dozens of LPG engines I worked on.

Spark plugs remain shiny new, oil stays crystal clear. But fuel mileage takes a 20% hit. When Mexico upgraded its fuels in the early 90s LPG became instantly obsolete IMHO.

Even though the 350 engines had induction hardened valve seats from the factory, they were not LPG use resistant. My truck had hardened exhaust AND intake valve seats. That engine cost almost $6,000 to build 27 years ago.

A vacuum valve safety must be installed to chop gas in event of an accident. I am relieved to be away from the burden of finding fuel and dealing with it.

For short interval generator start and stop LPG is hard to beat.