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.
