Would converting a gas GMC 454 to LPG be worth it?

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michelb

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Apr 8, 2007
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Hey,
  I was just wondering if you've heard of or considered converting a gas engine (e.g. GM 454 in my case) to run on LPG.  In my area, LPG appears to be about 25-30% cheaper than regular unleaded gasoline so someone driving 10k miles / year in a large RV would save $1k easy.

  I'm thinking that since motorhomes already have a large LPG tank anyway, it might not be that big of a job to do the conversion (don't know much about LPG conversions but I thought I heard/read that it's not particularly complicated (offhand, I would think that adding the tank/hoses/etc is probably a significant portion of the conversion) and you can keep them running dual fuel (in case you can't find LPG) Any thoughts? 

Let us know,
Mike
 
Remember you also get less power per gallon of LP, so some of the price difference is lost on extra fuel. It takes about 13 gallons of LP to produce the same amount of energy as 10 gallons of gas.

And a motorhome's LP tank is not large compared to its gas tank. Most Class A gas motorhomes have a 75 gallon gas tank but the propane tank is in the 20 gallon range.

There is a wealth of information online on conversion techniques, experiences, costs, etc.
 
Thanks for the info - I wasn't aware of the power difference so that might chew up a lot of my savings (if the propane costs 1/3 less but my mileage is 1/3 worse, probably not going to make a lot of difference).  Also didn't realize the tank size issue so I'd certainly need a larger tank ( I thought I had remembered seeing 80 capacity LPG tank, but it was probably 80 lbs not 80 gallons :( ).

Also found a few references to it in the forum in case any one else is curious but not a lot of answers (I have to get in the habit of doing search BEFORE I post questions):

http://www.rvforum.net/SMF_forum/index.php?topic=705.0
http://www.rvforum.net/SMF_forum/index.php?topic=8479.0
 
You would want to swap the gas tank for an LPG tank and that wouldn't be cheap to do.  With the lowered efficiency and conversion costs, I suspect it would take a long time to start paying off, if ever.  It's a decision more based on environmental concerns than monetary savings, much like solar power.
 
Hi Guys

A LOT of gas RVers go for the LPG tanks in the UK.

They have a new LPG tank fitted in addition to gas tank and std propane tank.

Yes, the LPG power is only 80% of gas power.

Even with our LPG at 80c/liter and gas at $2/liter - it takes a long time to break even.

With you prices being so close, I wouldnt bother.

Paul
 
Speaking of alternative fuels to beat hight prices, take a look at the 2 sites listed below:

Ever heard of "woodgas"?

All you need is a good supply of dry wood, usually cut into small blocks 2-3 inch cubes, as I remember.
Have seen trucks and cars in operation with that system in the 1940's in Germany, when I lived there as a child. Matter of fact, my Father had a small truck outfitted with it.

There are several articles found via Google.

Story 1 click here

Story 2 click here next

Probably good for a chuckle, but it does work. On an RV?  ::)

carson FL
 
I had a 74 Chevrolet pickup that I converted back in the 70s.  Put a 84 gallon tank in the pickup bed, a regulator and a carburetor unit completed the installation.  I ran dual fuel, two gas tanks and the propane would get me to Tahoe and back for snow skiing. Otherwise, I would have had to go to Tahoe and hope there would be gas available to get home.

The truck ran fine on both fuels, with a switch on the dash for the changeover.  Power and mileage was certainly less withe the propane, so I didn't save any money, but I did get to go skiing.

Finding a spot on the RV to hang an 80 gallon propane tank might be difficult. And like me, I don't think you would save any money.
 
Propane has less BTU/s than Gasoline so it takes more propane to do the same amount of work as Gasoline.  The results Caltex has reported is  a good example of what can be experienced when using propane.
 
A few years ago in Arizona, the state made the mistake of an enormous tax break for those that bought new vehicles that burned propane or natural gas.  These vehicles burned regular gasoline and the idea was that the folks getting these cars would burn propane for the environment and the ability to drive in the HOV lanes.  I see a lot of these vehicle filling up at the gas pumps but have yet to see one fill up at the propane pump.
 
Old topic, so sorry if that bothers anyone ....

I come at this topic from the perspective of someone who lived through the gasoline shortages in the late 1970s, and (okay, a bit of a survivalist mindset) considering the eventuality when gasoline is difficult to find, and whatever propane may be in the tank could be sufficient to get me ... somewhere ...

Just started researching, but I suspect that my carburated 454 could be a likely prospect.

Whether the cost can be justified in service of an unlikely scenario remains to be seen. May boil down to how much of it I can accomplish myself.
 
many years ago I drove a large crane truck in the mountains of Utah that was converted to gasoline/propane because of the Arab oil embargo.

even with a 2 stick 13 speed brownie trans and shifting like a mad man ....it almost didn't have enough power to get up a hill on propane.
 
Another benefit of the Propane is the engine lasts longer, a whole lot longer. So while the cost benefit may or may not work out for fuel cost and MPG if you plan on keeping the engine for a million miles you may come out ahead. 
 
NMDriver said:
Another benefit of the Propane is the engine lasts longer, a whole lot longer. So while the cost benefit may or may not work out for fuel cost and MPG if you plan on keeping the engine for a million miles you may come out ahead.
Click to expand...
This is very true. Oil will be as clean on dipstick at 50,000 miles as the day you changed it if you run it on propane only. I have 1974 1/2 ton pickup 6 cylinder, manual, plain Jane that I bought new and immediately converted to propane. ( gas crisis) Speedometer cable twisted off at 330,000 miles. ( scratched a mark on speedo face every time it rolled over) must have over 400,000 miles on it now. Engine has had plugs, points, wires, water pumps, starters, and alternators only for repairs.
It?s used regularly on Grandson?s ranch. Oil probably hasn?t been changed in 100,000 miles or so and uses none. I?m sure oil needs changing because Grandson starts it on gasoline in cold weather, then switches over.  I always plugged it in and tried to never to run it on gasoline.
 
jubileee said:
This is very true. Oil will be as clean on dipstick at 50,000 miles as the day you changed it if you run it on propane only.
Click to expand...

Only if you get the engine up to operating temperature and keep it there for a while.  Propane combustion produces water vapor and this will condense and collect in the crankcase unless the engine gets hot long enough to evaporate it.

I once took over maintenance of a 10 kw propane powered generator at a mountaintop transmitter site.  It typically ran anywhere from a few minutes to a couple of hours at a time during power outages.  The previous engineer poo-poo'd my idea of changing the oil because it looked so clean.  Water is heavier than oil, and when I opened the drain petcock the first thing that came out was about a quart of pure water, followed by a milky sludge.

Only the top 1/3 of what was in the crankcase was "clean" oil.  This is what showed on the dipstick when the engine oil level was checked.
 
caltex said:
I had a 74 Chevrolet pickup that I converted back in the 70s.  Put a 84 gallon tank in the pickup bed, a regulator and a carburetor unit completed the installation.  I ran dual fuel, two gas tanks and the propane would get me to Tahoe and back for snow skiing. Otherwise, I would have had to go to Tahoe and hope there would be gas available to get home.

The truck ran fine on both fuels, with a switch on the dash for the changeover.  Power and mileage was certainly less withe the propane, so I didn't save any money, but I did get to go skiing.

Finding a spot on the RV to hang an 80 gallon propane tank might be difficult. And like me, I don't think you would save any money.
Click to expand...

X2-

I too added propane capability ...... to my 6-cyl Ford service truck during the gas crunch so I could get to my customers (who were sweating in the Houston heat) rather than sit and wait in long lines to be allowed a 5 gal fill.  Once I got my propane mod installed, it was always a "zero wait" situation at my propane fill-up place .... nice.  At one point, I tried to increase the Ford's compression ratio to take advantage of the 110 octane rating of propane (with the idea of running on propane only) but no pistons etc for that mod were available off-the-shelf ..... the parts houses said "hot rodders aren't much interested in 6-cyl Fords".  lol  I had a manual shift with overdrive and, with both tanks full, the range between fill-ups was phenomenal even though the MPG with propane was about 20 percent less than with gasoline.

If I could even find a place to put that huge steel propane tank in my coach, I'd probably be at the GVWR before I stepped on board.  :D

Safe travels, all.
 
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