Smokstak Bulletin Board

Running Engines on Propane

Well I seem to have caught this propane bug that’s been going around and I am toying with the idea of running my 6 horse M on the bottle. I think I can make a plate for over the compensator and plumb the bottle up there. I am hoping to be able to start the engine on gasoline and then after things warm up a bit and even out I want to be able to switch it over to propane. What I need to know is this: do I need to change the magneto timing to run on propane or will the same settings I use for gasoline work for propane? It occurs to me that propane engines don't run well with the timing advanced, but I am not sure. – Joseph

Joe, I ran my six horse M just the other week on propane. The timing was still the same as always when I run the engine on my special mix (half lead free gas and half paraffin). We always use a special regulator when running an engine on propane, see the picture. The RED one is a pressure valve and the BLUE one is a suction valve. The engine was running on kerosene and I put the hose in the opening of the damper plate when it was closed, closed the kerosene needle valve and there she ran on propane without any trouble, but much slower and nice and quietly. I adjusted the damper plate a little more open just 1/8" and the engine ran like a clock. One of these days I will make an adapter plate instead of the damper plate with a built in tube for the propane and a little adjustable air inlet to regulate the mixture. -- John

I always start my propane fired engines on gasoline, then switch over to propane once they are running. On IHC M's this would be really simple to do, since you already have that priming bowl in the mixer. The trick that I have found helpful is to shut off all possible air. Only feed the engine propane and it will suck air from somewhere, like around the valve guides. This way you only need the smallest amount of propane to make your engine run. Propane has something like 35 times the BTUs of natural gas and only needs a very miniscule amount of air to combust. Once you have your M running turn your gasoline off and turn the propane on slowly. When you can hear the propane "hisssssssss" that’s more than enough. Make something to go over the carb/mixer so it cannot suck any air. You will be surprised at how long an engine will run on a 20lb bottle of propane when it’s done this way. And talk about running SLOW! -- Doug

John, how does the suction valve work? -- Bob

With an open bottle there will be no propane coming out the hose, when you push the little brass pin the propane is flowing. At the inlet stroke the engine sucks the valve open and the propane comes in the mixer, no more, no less. The faster the engine runs the more propane coming out the bottle. When you pull the hose out of the mixer, then the flow stops immediately. -- John

I have never heard of a doodad like that John. What do you guys use them for and what do I need to tear apart to find one? I was just going to use a barby regulator, a ball valve for on and off and a needle valve to regulate the flow. -- Joseph

These regulators were used on the English Wolseleys, mostly for the little milking units in the field. So now and then they show up on the market, but they are scarce. Through these valves you never get propane gas when it is not needed, only when the inlet stroke is there. One of my engine friends runs a Baker Monitor on propane with the same valve unit. You can see the flywheels spinning very slow and hear a little hissing that's all. Some guys use an old LPG car unit that works the same. -- John

On a hit and miss governed engine that "demand" valve is necessary. Valves like this are similar to what is used on LP powered tractors and forklifts. On a throttle governed engine this isn’t needed unless you plan to actually work your engine. Or if you don’t want to work your throttler, but just make it run slow, a demand valve isn’t needed. You can simply use a regulator off a BBQ. Some BBQ regulators have a valve in line after the regulator. This way you only have to turn the main valve on and then feather how much propane you want by the little in line valve. And since propane burns so dry, it is a good idea to plumb in a drip oiler in the fuel line itself. And remember, shut off all air intake as best you can. -- Doug

Check with your local power company, and ask where they get their propane powered equipment serviced. The repair shop should have the regulators you need. Especially when cool, you need to preheat the engine before running on propane. Also there is a 25% power loss, as well as a 25% more fuel used penalty over gasoline. One more Item - propane also increases wear throughout the engine - valves, seats and rings, as propane runs hotter and has no lubricating value, unlike gasoline. -- Andrew

I had real good luck running my 6 horse IHC M on propane. I used a barbeque regulator and a hose I picked up at Lowe’s. I removed the mixer/carb and made a plate that bolted on there, drilled and tapped it for 1/4 pipe threads, put a nipple in and then a tee. On one side of the tee I put a ball valve to control the air and on the other side of the tee I put a needle valve to control the gas and then I hooked the regulated flow from the bottle up to the needle valve. I used the same timing settings as I would use on Gasoline. You will have to feel it out to see what air/gas settings work for you, but with the help of a friend of mine we were able to get it to run very slow. I think it is important to be able to adjust the gas and air separately. – Joe

You should not use a regulator that provides a flow of propane when the fuel tank is turned on. All motor fuel vaporizers/regulators lock-up (no fuel flow) until the regulator senses a vacuum from the engine. When it sees a vacuum, fuel flow will start. If you are running this engine with the type of regulator you are speaking of and the engine stops (while you have been called away at a show) you would have a dangerous fuel leak. If you want to run LP, please use the right equipment. -- Kent

I agree, but you should NEVER leave an engine running when you are not there. That is just asking for trouble. -- Patrick

I’ve hooked up my Ideal to run on propane and I had great success in running it slow and steady. But that doesn’t make it correct or safe. The barbecue regulators with a needle flow control will work with no problems, but they are a safety issue. You need a regulator that has a "vacuum controlled flow" otherwise you’re making a potential bomb as a previous post stated. I swapped my Ideal back to gasoline until I can acquire the proper regulator. I did notice that the engine ran much hotter while just idling when operating under propane. Probably not a major issue at an idle, but I’m sure its a factor to consider if a load demand is added. -- John

Some manufacturers built mixers that piped fuel straight into the mixer without an "on demand" regulator. Commercial was one such manufacturer and I think Western did the same. The danger of such a setup has been greatly overstated. The amount of fuel to run a mid sized engine is very small, much less than required to fuel your hand-held propane torch. Would a propane torch, with the valve cracked partially open, sitting out in the show grounds be considered a "bomb" or an extreme hazard? No. The fact is, you probably would have a hard time lighting it without getting the striker right down on the nozzle, and then you'd only have a small flame. I kludged together such an arrangement on a Sampson engine, essentially a 3/4" pipe with a valve on one end to choke back the air. In the middle of the 3/4" pipe I've stubbed in a 1/8" pipe where the propane enters. The propane is controlled by a smaller valve and pressure is controlled via a barbeque regulator. A barbeque-sized bottle will fuel the engine for a several show days. Go ahead and get yourself some pieces of pipe and some valves. It's not as difficult as you might think. – Rob

Rob, all I can say is your right a small leak in the middle of a open field won’t do anything? You do this in your shop or garage and you maybe building a new shop as soon as you get out of the hospital, if you’re that lucky! Like everything else practice safety! That way you won’t be a statistic and we won’t have to deal with the lawyers and O.S.H.A.! Propane is bad because it lies on the ground and you may not even smell it until it’s too late! – Bob

Hello from Wisconsin! I have run my engines for a number of years on propane. They should always be run with an "on demand" regulator. This works just like a needle seat and float in a carburetor - it stops the flow of fuel when there is no demand. The on demand regulators can be purchased at your local propane dealer. Ask for model SD made by Garretson Equipment Co. – anon

I agree with Bob saying "The danger of such a setup has been greatly overstated". We all do things that can hurt or kill us daily. How many of us ride motorcycles or fly airplanes? Some of us wouldn't do this but would play with propane. Some of us wouldn't play with propane but would ride motorcycles and fly airplanes. How about putting propane in air conditioners as a refrigerant? Lots of folks do and they will tell you that they would rather take that risk than the risk of cancer using R 134. Both are risky but I don't think any of us would not have air conditioners to eliminate risk. How about going down a narrow winding road meeting a logging or oil well rig truck traveling at hi way speed and meeting them just 4 or 5 feet away? You have no control over their action or condition of their truck. Life is full of dangers. What one may think is dangerous another may not. I've had some people tell me that my engines are the most dangerous hobby they ever saw, but I'm still going to run them in a way that is safe to me. That way may not be safe to others. -- L.D.

Well after a bit more thought maybe the propane hazard is overblown. Look how many engines you see that are weeping gasoline. Generally we don’t seem too concerned. That’s why I converted my Ideal to propane as the vertical intake guide was always dripping gasoline. Later on, a replacement valve guide reduced the drip to almost nothing. Other factors might make a difference if anyone can offer some up. So, I guess propane vapors or gasoline passing by piston rings in a flooding situation in an enclosed crankcase are equally as risky. If anyone can offer more insight on this issue don’t be bashful. -- John

I didn’t say anything about this being overstated and anyone that thinks it is could end up dead wrong! A gas leak is a gas leak no matter how small! In an area where it can collect like a closed building, it WILL blow up under the right conditions. You’re right, there are a lot of things that aren’t safe and leaking propane is right at the top of the list! Propane appliances cost more then natural gas ones because of liability and comparing a flooded gasoline engine to a 20 or 100 lb. bottle of propane with a constant leak is not much of a comparison! -- Bob

Bob, that statement, "The danger of such a setup has been greatly overstated." was copied and pasted. However, I did make a mistake because it was Rob that said that and he is who I was agreeing with. I apologize to you and anyone else I made to think that you said that, you did not. In fact I feel your opinion is 180* from that statement.

Thanks to all who replied. It wasn’t my intent to start a safety debate, but the points brought up are all valid. Thanks again and Happy Holidays, -- Jim


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