The Stovebolt Site Forums The Shop Area General Truck Talk Propane or natural gas.

What's involved in running a 'bolt 235 on Propane or natural gas?

you need the kit to convert carb, by pass fuel pump, and a fuel preheater [for propane at least, just a heat exchanger using rad water], and of course an approved tank ... kits are made for 1 and 2 barrel jeeps, so it should be possible

lotsa folks on propane up here - the bus I got previously had a 454 on propane

Bill

I had a 76 3/4 ton on natural gas, problem was not enough gas stations for it and it only had a 100 mile range.I just quit using it.
Lothar

I thought there were some ignition/timing mods needed too.

Stuart

Natural gas is great if you're a commuter driving everyday. It's a dual fuel system. Gasoline and natural gas. A flick of the switch and you can't tell the change over. I kept about a quarter tank of gasoline all the time and once in a while ran it on that to keep the injectors active. Fuel injector cleaner was needed more often too. Natural gas has it's drawbacks as KillerKnight just said. The tanks are very heavy and, in a car, needs heavy duty springs.
I had a Crown Vic on natural/gasoline and drove it 60000 miles. It's an expensive conversion but in my case there were grants available that helped the initial cost by a large amount. I was able to get a payback in 3 months. A round trip of 120 miles provided a saving of over 50%. There was a fuel station at either end of my trip so it was convenient for my purpose. When I moved from Ontario to Manitoba there weren't any fueling stations available so--no more natural gas.
There was a noticeable power loss on natural gas as well, but for highway cruising it was just fine.
Geo.

Any system that puts the fuel gas through the throttle body displaces some air, which is responsible for the power loss- - - - -not enough oxygen to burn the fuel efficiently at high flow rates. I participated in some liquid-propane injection research that had lots of potential, but it resulted in major icing at the intake manifold because of the refrigeration effect of vaporizing the propane in the intake manifold. It would take a water-heated injector rail, and even then, warm-up would present problems.
Jerry

hey fella's I am a well tender for a natural gas company and I have several different type's of engine's that I maintain that are now running on the natural gas , I can tell you that no modification's to ANY gasoline engine is needed to run it on natural gas over just figuring out a way of getting it into the engine ,
I have small engine's that have a gas tank for gas and a hose for the natural gas flip a switch from one to the other and the engine never know's the difference ,,
my compressor's run 24hour's a day 7 day's a week and you take out a spark plug that is 6 month's old and it look's like brand new !!!
a small 5hp engine takes about 2 to 3 pounds boost (psi) to run , a bigger engine like a big cat six cylinder take's about 15 pound's
it is something that can and will work ,,,

Dumb question for all you guys. In the 70's there were LNG and propane conversions done all over the place. The Los Angeles times ran every one of their newspaper delivery trucks on one of those but can't remember which one. It must have been safe because one of their trucks came in for repair having had the pressurized tank knocked completely off the truck. Nothing blew up. A few indivuduals converted cars and even small Toyota trucks placing a small tank accross the bed up near the cab where a tool box would go. My question is, what the heck happened to that technology and why was it abandoned?

I still see a lot of fleet trucks around here running LNG.

I've seen a lot of forklifts that burn LNG.
I wonder if I could get some parts from a forklift junkyard.

no reason why not Jim, my forklift runs propane in the little 1 bbl 4 cyl engine, not too different from a 235

Bill

I used to maintain a fleet of trucks for a big co. Against my advise some yuppy in a plush office decided to switch all the trucks to propane. It turned into a disaster. Ther drivers didn,t like it because it was a nuisance to fill & if you ran out you had to be towed in. The converted fuel system was troublesome & you couldn,t keep valve seats in them. A valve job lasted about 10,000 miles on the fords & a little longer on the chevs. They soon converted every thing over to diesel like I recommended in the first place. That,s why you don,t see them anymore.

Seems to me I recall a problem of burned valve seats being the demise of propane conversions. Another dumb question: why is it that this occurs and why hasn't someone engineered a fix for this? I think they use propane on towmotors because they are used indoors in warehouses and you can't have the products of combustions from a gasoline engine indoors. Why is it that those towmotors seem to last forever burning that stuff but cars/trucks get burned valve seats? I guess that's actually three questions...

The answer to your Questions is really simple LNG and Propane are a Dry Fuel (no lubrication) and industrial application normally dont run the RPM's for the duration that automotive applications do, the old towmotors ran the Continental engines and when on propane it would beat the valve seats out not burn them because the valve guides would wear out (back to no lubrication) and the valve rattled around like a BB in a Box Car. When these engines needed overhauled it was a major overhaul. Our engines were designed to run on Gasoline and any other alternative fuel is going to decrease the life of that enging, I can remember when 100,000--124,000 miles was just about all you could get out of a engine. With Fuel Infection 250,000 + is common, at todays prices it's $5,000 and up to replace the engine, and if we increase the demand on LNG or Propane the price will go up (same as gas, supply and demand) then it's going to cost more to heat your house. Vicious circle. Just Venting thanks for listening.

on the burned valve subject you guy's are talking about PROPANE ? right ?
I don't know anything about it but I do know first hand that natural gas and methane do not have this problem because I have one compressor that is about a 300 horsepower straight six engine and I have been maintaining it for three year's it run's 24 hour's a day 7 day's a week 365 day's a year and the head has never been off it ! so the natural gas is not going to cause engine trouble and in my opinion it will save engine's because it burn's so clean , when they change oil in these motor's the oil look's just like new oil it never get's very dirty ,
I don't really understand why propane is causing the valves to go bad unless it making the engine's run hot some way ???

with lots of folks in my area running propane, I've never heard anyone mention burnt valves/seats, and my forklift has been on propane for decades, runs fine

Bill

I am assuming that the compressor is a diesel conversion, it will have oil sprayed on the bottom of the piston's sodium valves and hard seats and probally only runs in the neighbor hood of 1900 RPM, that conversion will live a long time but automotive conversion rely on petroleum fuel to lube the guides. It is just my opinion that converting to alternative fuels is not worth the money. They have oil injection kit's for propane/ LNG that extends the enging life but that is an added expense and another maintenance problem. If you can make it work that is great, but the more the demand on LNG and Propane the price will go up that is just supply and demand, kinda looks like we are between a rock and a hard spot.

the compressor's are plain gasoline engine's with a metal tube stuck in the air flow just under the air filter before the butterfly in the carb , all that would be needed to put them back on gasoline is a fuel line and gas fuel tank ,
the smaller one's even still have the gasoline tank but it has a switch to turn it off ,,,

Interesting subject really. Especially in light of recent gas prices but hey, we were saying that back when you had to wait in line for gas on your license plate day. How will this all shake out guys? I expected to be driving like George Jetson.

Over here there are still a lot of vehicles converted to LPG (propane) - petrol is over $6 US gallon equivalent here; LPG is about half the price. There were conversions done in the late 70's & into the 80's that did have a valve recession problem; but with hardened seats fitted, they were fine. I think all vehicles today have hardened valve seats anyhow.
I've been told that there was also a problem on earlier conversions where certain alloys in the bearing inserts would be eaten away by the LPG but apparently this is no problem today either.

I have been driving forklifts of every size and capacitiy for over 35 years now and every one of them were propane/lpg powered. Many of them ran 24/7 and to my knowledge there were never any engine failures of any sort that were related to the fuel type. My 3 cents
David

Having said that, though...I think if I were considering running my 261 on propane, I would most definitely put unleaded valves and seats in the head. I really need to do that anyhow, though.

When I was stationed in Athens Greece in 1980-81 they had over 10,000 taxi cabs and they were all ordered to convert to propane. THEY took measures to cut the pollution way back then and it worked fine!!

Low speed engines run forever on propane, it is very clean also. But work a truck or car hard on it & it beats the valve seats out, unleaded or not.

Why not just inject a little bit of two stroke oil? That should take care of the valve seats. 200:1 or so should be plenty. You could modify an RX-7 oil metering pump for the task.

Prior to unleaded gas, the tetraethyl lead anti-knock additive also "cushioned" the valve from the seat. When they phased out these types of additives, we were left with unleaded gas. Without this cushion, the valves would recess the valve seat leading to ruined heads and burned valves. Some engines have replaceable valve seats (even a briggs and stratton) but most have the seat cut into the head. One fix for this was the use of a stellite torch to hard face the valve seats, then do a valve job, lots of harleys had this done. Post Unleaded engines have their metalurgy adjusted for this difference. LPG and LNG do not have any lube characteristics for valves. BUT, I have seen IHC binders run on that LPG for a lifetime (100+k miles) Incidentally having 20k mileage oil that looked as clean as when it was put in, although its lube characteristics had to be diminished. Put a properly designed LPG or LNG system on a modern engine and you will have a sweet clean runner. Both have less BTUs per unit than gas so power will suffer. On an older truck, put on a kit designed for the approximate CID and drive it. Heads are cheaper than stellite or inserts, find an extra head, IF you ever have a problem, put it on.

Propane is an extremely clean fuel, but you lose horsepower and mileage. This is compensated by the fact that you can run much higher compression ratios on propane. I have personal knowledge of a big block Dodge running 13.5:1 with no problem. I wouldn't think it would be worth the cost of the conversion and inspection if the vehicle wasn't a daily driver.
Bob

Have not been associated personally with CNG.

As far as LP goes: Some hotshot government whizkid convinced several school districts in this area to convert buses to LP several years ago. Result: every single bus either got an engine rebuild, a new engine, or the bus (if old enough) was scrapped. Valves receded through the heads into the pistons in less than one school year. Like to bankrupted several school districts.

Also have personal experience with a factory dual fuel motorhome 454. Mileage on regular gasoline was 9.7 MPG (yes, we kept records). Mileage on LP was less than 4 MPG. Power dropped by about 40 percent. Again, this was a FACTORY dual fuel, Dad bought it new. With a 40 gallon propane tank it was impossible to drive 100 miles!!!

In Missouri, there was also a $110. license annually for using LP. Even when Dad stopped using the LP, he still had to pay the license until the LP tank was removed from the vehicle. Then the vehicle had to be inspected prior to waiving the license. Plus, road tax was added to the cost of the propane.

We got it off before it did any engine damage, but definately not a cost effective unit, even if propane were only 25 percent the cost of gasoline, and the conversion was free!

Jon.

I worked for several years as a mechanic on a fleet of CNG/unleaded police cars. Did not see the valve seat problem some have mentioned here. However I would stay as for away as possible from any conversion to CNG. It works fine on an engine designed for only CNG fuel.
A conversion will work but most likely you'll be unhappy with it. If you must do it here is my advice:

#1 you will need to advance the timing an additional 8-10 BTDC. If you don't it won't run for crap.

#2 You will need to change your plugs every 10k miles and only use top quality plugs, wires & coil. CNG fuel needs every bit of fire you can get out of it to run well.

#3 DON'T pump the gas when starting!!! It will have a tendency to backfire through the carb(injector depending on what system you use). Our shop record was about 100 ft from the car where the airbox landed.

#4 If you have to pass a state emmisions test switch it over to unleaded for the test. Unless the ignition system is perfect CNG runs in a constant state of misfire & will fail the emmisions test for excessive HC. switch it to unleaded & it will sail through. I lost count of how many cars the cops brought in for emmision test failures that I just switched fuels & retested OK.

#5 Look up GFI or Mogas. they are 2 of the major manufactures of conversions. I think they are both out of Canada. they should have some good info on how to make the systems work. Of course they will blow lots of sunshine up your skirt to make you think the systems are the greatest thing since sliced bread. :rolleyes:

#6 Pray always. You may even make it home from your drive occasionally!! :p

Good luck

My son-in-law works for the local bus system FAX (Fresno Area Express) and they are in the process of converting their whole fleet of over 120 busses to CNG (Compressed Natural Gas), and have no problems related to fuel. Their mileage is short of the diesel power and power is down and the fuel system costs a lot more around $100,000 per bus, but local politicians thought they are doing the environmentally correct thing (even though actual tests show that diesel engines of today burn as clean as CNG and have more power and better fuel mileage). Seems like any "alternate fuel" just doesn't perform as well as petroleum products.

CNG in a Police car, there is no way anyone could get me to go on a call when they said "Shot's Fired" no way. Wonder if the Workers Comp payments went up. May not be any more dangerous than gas but it is the thought.

Our dept tested the tanks by firing various caliber rounds into them before they agreed to convert them. Nothing pierced the tank enough to be dangerous. A lot of officers complained because they worried they would get stranded by a no start in a scary situation. I don't know if it ever happened. Once we started using dedicated CNG only cars from the manufacturer we had a lot fewer problems.

I tore down a propane 283 chevy my dad drove daily for 10 years in a 75 4x4 chevy scotsdale, 6 years with the same oil, no sludge, heads were ok, everything was ok, except the power loss and the worn out oil pump that made a rod bearing go bad. Not a great idea for pulling power, but propane used to be CHEAP, so we just pulled slow.

I have seen many of the difficulties stated by others, and I know some of the advangates of cleaner oil and generally longer spark plug life, but with loss of power, increased fuel consumption, and the potential for valve trouble, the cost of conversion is difficult to justify. I would not convert a functioning gasoline engine to propane, or CNG either.

Harvester

After reading all these comments and situations which differ in there outcome I cant help but think that RPM and heat are a factor that plays into failure.
Propane tractors,like my 1956 JD 60, have been running for decades and are still running along with fork lifts and other motors.
Tractors dont run High RPM, so is that part of the win situation ?
I do believe one thing....The day after we figure out a cheaper fuel they will raise the price of it !
Unless we make our own fuel.
A dime for my thoughts,a penny don't doesn't do it anymore.
Dan

If you're in the midwestern states, you should consider E85.
In order to take advantage of E85, you should build your motor for high compression. 12:1 would be good, if that's possible on a stovebolt. 105 octane is wasted at much less than that compression level.

Lots of pros and cons for sure....Apparently some have converted from gasoline to propane successfully and others not. The latest thing I read about just yesterday is using anhydrous ammonia as a motor fuel. Here's the URL . The developer/seller makes a convincing argument, but....it's got to cost something to convert, not to mention the current state of law....I think right now it's illegal to own NH3 without a permit due to the proliferation of meth labs.

Propane would be extremely simple to add to your truck and a mono-fuel conversion would be similar to the 1963 Rambler Conversion. As mentioned earlier, you will need a propane carburetor, converter, fuel lockoff, and a fuel tank. Your propane fuel economy will likely be 75-80% of your gasoline economy. Ideally, your timing advance would have to recurved to have optimum fuel economy. Dual fuel is another option.

As for earlier points about propane-fuelled engines, there is a slight power loss for two reasons: propane (as a gaseous fuel) displaces some air from the combustion chamber and propane mixers typically only provide the maximum power fuel mixture at maximum air flow. The air displacement (~4% compared to less than 1% for gasoline) results in a loss of volumetric efficiency. The lean fuel mixture at low RPM is due to the design of the gas metering valve in the mixer.

Also, propane's effect on exhaust valve seats is similar to unleaded gasoline. The reason people have burned exhaust valves is because they set the fuel mixture too rich. Propane responds opposite to gasoline because liquid fuels provide an evaporative cooling effect while gaseous fuels do not. It is always safer to run leaner fuel mixtures in a propane engine.

The only reason to convert is for economic reasons. If you drive a lot and there is large enough difference in price between propane and gasoline, a conversion could make sense for you.