LP vs. Gas

[joraz]

I'm thinking about buying another rig (sold ours six months ago). This rig is a GMC (1976) with an Olds 455. It's low mileage and has only run on LP. I've got a couple of questions:

1. Other than it being less efficient are there any negatives associated with running on LP?
2. In that this rig has been running only LP, other than rotted gas line, what other problems might I encounter?

Thanks.
jor

[SaltiDawg]

dougrainer wrote:
...Are you positive that it has been outfitted to ONLY run on LP...

Doug,

The OP included, "other than rotted gas line" was the clue that it had been run on gasoline originally.

[Kayteg1]

I used to have forklift with Nissan engine converted to propane.
That thing was about 30 years old, sitting for 6 months at the time, yet starting after couple of seconds every time, beside the time when I wash the engine and got distributor wet.
Good part of propane is that is not aging, what on rarely used forklift was big plus.
Negative part it was hard to start in cold weather.
I know professional systems in cold weather use gasoline to start and after the engine reaches certain temperature, it switches to propane.
Modern car conversion in Europe runs about $3000

[thomas201]

I was an oilfield hand, retired Petroleum Engineer, and the biggest problem was that cooling in gasoline engines depends on vaporizing the gasoline. The heat absorbed really adds up. So a converted engine needs extra heat removal, to run on nat. gas or LPG, plus special alloys in the valves and seats.

So your question is, was the work done right? Otherwise run it on gasoline.

Converted Kubota diesels worked good for us, Honda gas engines not so much.

[joraz]

Pemex NOVA almost gasoline

I bought many gallons of that Nova (we used to call it no va) back in the late 70s and early 80s. My old pickup would run on (and on). Kinda hard to turn off an engine using that stuff. I'd take it out on a lonely two lane and blow it out from time to time. Sure was cheap though. A friend of mine bought a little diesel Le Car and used to drive between Presidio and El Paso, Texas. He'd fill up in Mexico at I think 13 cents a gallon and make the trip for less than $2.50.

Thanks and I will check for detonation.
jor

[MEXICOWANDERER]

Make DAMNED SURE the engine does not DETONATE (like pinging but much worse) going uphill under load in hot weather. Some engines tolerate LPG motor fuel, others do not. The MoPar 440 L3 engine is one that cannot be "fixed" to cure detonation. I drove a customized 350 Chevrolet in Mexico for years before gasoline improved. An incredibly expensive modified engine. Hardened intake and exhaust valve seats, Venolia 12.5 to 1 pistons, a custom one-off Bruce Crower camshaft, and a 5-row high fin and tube count radiator and engine oil cooler. The engine ended up with as much horsepower as a 275 horsepower 350 gas engine. The radiator threw an immense amount of heat, all lube oil sealing gaskets leaked even after a $200 set of Mr. Gasket silicone gaskets were used. The engine used a dedicated IMCO 425 LPG carburetor and had an extremely modified HEI distributor with 44 degrees of total advance. Unloaded the pickup got 10-3/4 MPG.

I was satisfied, because back then crooks diluted Pemex EXTRA gasoline with Pemex NOVA almost gasoline. And LPG motorfuel cost .45 cents US per gallon. But when Pemex introduced MAGNA SIN gasoline and made the price of it and NOVA so close, diluting became unprofitable, the value of my LPG power became less than useless - it was a giant liability.

To me, LPG is an ideal "short run" fuel for generators, if the LPG tank is large enough to not need refilling during camping. Generators can be started and stopped, spark plugs retain white center electrodes, lube oil remains crystal clear and a thousand starts and stops only wears on the starter motor.

But after owning a converted Superior school bus that was LPG and the pickup truck, a person could not give me another LPG vehicle. I have fought underpowered overheating Onan gensets, Wisconsin powered gensets and have settled into decidedly biased opinion about using LPG as a motor fuel.

[time2roll]

LP is not less efficient as much as LP just has lower energy per gallon vs. gasoline.

If you expect to use only LP that is fine but if you expect the gasoline system to work you had better give that a test drive.

[joraz]

Are you positive that it has been outfitted to ONLY run on LP?

I should have taken more care in my post. It is, indeed, dual function. The owner ran it on LP rather than gas. Thanks to all.
jor

[Chris_Bryant]

Like others- I have seen only dual fuel rigs- usually with big P tanks.
Other than simply finding LP, there is a road tax issue- legally you must find a dispenser who collects road tax for a motor vehicle, depending on the state.

[wa8yxm]

I think the major issue will be finding LP.. Not all places have it.. So when you travel plot 1: Places that SELL LP and 2: Places LP is prohibited.

Like others, Have never seen a motor home fueled by LP but.. I have seen LP conversion kits for car engines...

LP has less "Punch" than Gasoline so for any given engine size climbing hills may be harder.

LP is more enviormentally friendly and generally the engines run with less noise (For the same reason it is harder to climb hills).


My Dad was a well tender (Oil well) for several years.. That single lung engine ran on LP.. 300 gallons of it.

[red31]

Finding LP on Sundays can be an issue.

[dougrainer]

I have never seen a Motorhome that runs ONLY on LP. Especially a Vintage GMC. They were built on Gasoline and conversions to run Dual LP/Gas were common back then. Are you positive that it has been outfitted to ONLY run on LP? There is NO Gasoline tank? What about the slide drawer 6.0 Onan? Does it run on LP also? The problem with running on LP ONLY is simple---You would need an extremely LARGE LP tank/s to go just 100 miles. That is why dual LP/Gas were the way to go. Doug

[romore]

You may have problems with the heads, engines of that vintage didn't have hardened valves and seats. Valve guides didn't last long either, LP is very dry and caused the oil to break down.