ebinmaine 67,484 #1 Posted July 3, 2022 After having written conversations with @Jrain @Handy Don @Snoopy11 @Pullstart @Jeff-C175 @Oldskool on the subject I thought I'd bring it in here. I'm curious to know whatever info is out there about changing an OE built propane engine to a gasoline burner. I read that propane is higher octane and cleaner burning but produces less energy than gasoline. If an engine is rated to a specific HP is that actually based on the propane? If so does the HP increase when changed to gasoline? Any info on what parts are needed? Carburetor obviously. What else? Thoughts comments questions suggestions opinions..... 2 Share this post Link to post Share on other sites
Handy Don 12,217 #2 Posted July 3, 2022 Initial thought on horsepower is to look at displacement and valve configuration (L-head vs. OHV) and assume that where comparable, the horsepower would also be--with the proper carb. 2 Share this post Link to post Share on other sites
ebinmaine 67,484 #3 Posted July 3, 2022 22 minutes ago, Handy Don said: Initial thought on horsepower is to look at displacement and valve configuration (L-head vs. OHV) and assume that where comparable, the horsepower would also be--with the proper carb. That's part of my curiosity... Gasoline and diesel have about 30% more energy than propane. But.... Propane has a higher octane rating so produces well. Seems to me an identical engine fueled by gasoline would make slightly more HP. For the record it doesn't much matter to me. It's just a curiosity. 1 Share this post Link to post Share on other sites
ri702bill 8,319 #4 Posted July 3, 2022 (edited) 33 minutes ago, ebinmaine said: cleaner burning but Propane has no lubricating quality to speak of for the valves, unlike old outdated leaded gasoline. That being said, I believe the valves & seats would survive just fine on unleaded fuel. Fuel pump?? Just a tank regulator on propane... Bill Edited July 3, 2022 by ri702bill 1 Share this post Link to post Share on other sites
ebinmaine 67,484 #5 Posted July 3, 2022 9 minutes ago, ri702bill said: Fuel pump?? Yessir. Likely go to Facet electric there. 1 2 Share this post Link to post Share on other sites
ZXT 2,401 #6 Posted July 3, 2022 Look at dual-fuel generators. They all are rated at slightly higher KW when running on gas vs. propane. They're also likely a good example of what parts you'd need. 3 1 Share this post Link to post Share on other sites
ebinmaine 67,484 #7 Posted July 3, 2022 4 minutes ago, ZXT said: They're also likely a good example of what parts you'd need I thought so too but I'd want to change specifically to gasoline. Dual fuel setups I'm not opposed to... But that's more parts and maybe more expense? 1 Share this post Link to post Share on other sites
Oldskool 6,644 #8 Posted July 3, 2022 On a small engine what do you suppose the HP gain would be? 3 or 4 ? Would the propane be less problematic in the long run then gasoline? No stale gas, less mess, no water in the fuel? 3 Share this post Link to post Share on other sites
ebinmaine 67,484 #9 Posted July 3, 2022 9 minutes ago, Oldskool said: On a small engine what do you suppose the HP gain would be? 3 or 4 ? I'm only guessing here... If a gain of 20% is realized by changing from propane to gasoline.. A 30 HP engine would go to 36. But the BTU is 30% higher so maybe 20% is a low-ball?? 1 Share this post Link to post Share on other sites
pfrederi 17,739 #10 Posted July 3, 2022 Old farm tractors could be had that ran on propane. The had unique heads that made for higher compression. These heads are now very popular with pullers as when you run gasoline you get much more power than with the standard gasoline head.. 4 Share this post Link to post Share on other sites
ebinmaine 67,484 #11 Posted July 3, 2022 41 minutes ago, pfrederi said: Old farm tractors could be had that ran on propane. The had unique heads that made for higher compression. These heads are now very popular with pullers as when you run gasoline you get much more power than with the standard gasoline head.. A factor I'd forgotten about there. So I wonder if one switched TO gasoline on a propane designed engine... How would that be compensated for? Or would the 90+ octane be enough? 1 Share this post Link to post Share on other sites
pfrederi 17,739 #12 Posted July 3, 2022 (edited) 22 minutes ago, ebinmaine said: A factor I'd forgotten about there. So I wonder if one switched TO gasoline on a propane designed engine... How would that be compensated for? Or would the 90+ octane be enough? Pullers all run High Octane non ethanol fuel. Question might be was the engine really designed for Propane (hi compression head, domed pistons) or just modified by replacing fuel setup. like the dualfuel that have lower output on propane. They do not seem to have special heads.. or they would need premium gasoline Edited July 3, 2022 by pfrederi 2 Share this post Link to post Share on other sites
pacer 3,169 #13 Posted July 3, 2022 This is not going to give you any info but I thought it might be interesting.... Years ago I ran a 'dooky' business (Septic tank clean out) seemingly I always needed a 'new' truck. Spotted one at a propane dealer that they had removed the tank from and was for sale at a very reasonable price ... the kicker? it ran on propane! So I thinks that cant be tooo bad a thing and bought it. It had been set up to use the propane by simply sticking a hose in the existing carb with a solonoid keyed to the switch that would start the flow of 'gas' when starting. Put my tank& pump on it and filled up with propane (no gas gage) and started my rounds .... kinda underpowered but not to bad until ----- I was headed home and it quit on me.... I'm thinking, what the!! It was out of 'gas'. Where I could normally go an easy 2-2 1/2 days on a gasoline engine here I hadnt even finished one day! To top it off, I had to just 'coast' off the shoulder of the road as best I could leaving he truck about half still in the traffic lane. Call my wife to come get me so I could get a buddy and we would go and pull it home with my second truck ---- Get back there .... and the truck is GONE!! Staties had already got it towed to impound! Cost me $250 to get THAT fixed!! Anyway, back to the propane... since it was just a hose stuck in the existing carb (Ford 390) I set out to find a 'gasoline' tank and within a few days I had it going on gas ... and it ran fine! Bit more power, ran my usual 2 2/12 days on a 50 gal saddle tank, nice truck! So from my experience here switching from propane to gasoline was .... rather uneventful! 1 Share this post Link to post Share on other sites
clueless 2,991 #14 Posted July 3, 2022 (edited) This is from the US Carburetion site they sell duel fuel propane kit for small engine gas generators. Propane only has about 10% less Btu (energy) content than gasoline gallon-to-gallon. So horse power differences are small one way are other, unless you running the 1/4 mile. I bought my first kit from them 15 + years ago for my 10hp Coleman Tecumseh flat head genny, it took a little adjusting to get it running good, but it ran fine for 4 days after one of these squalls (Cat 1 Hurricane) we get down here. Here is some more info from their site for propane generators that is useful to know. It requires 2 hp to produce 1000 watts of energy per hour under load. Under load each hp consumens 10,000 BTU per hour. Propane contains 92,000 BTU per gallon (NOT POUNDS). Now if you have an idea of how many watts you will use during an outage,( you can Google house wattage charts, they can bit different in how many watts some appliances use but this is a bit of a guessing game anyway) and if you made it through 10th grade math you can get an idea of how many gallon (NOT POUNDS) of propane you need per hour. Ed, sorry for hijacking your post but It is Hurricane season for some of us and this may help some who are thinking of buying a propane generator or have one. If you don't have one and you live in a Hurricane area I highly recommend a 12 to 15 hp portable propane generator. Edited July 3, 2022 by clueless 2 Share this post Link to post Share on other sites
ebinmaine 67,484 #15 Posted July 3, 2022 26 minutes ago, clueless said: sorry for hijacking your post but It is Hurricane season for some of us and this may help some who are thinking of buying a propane generator or have one. If you don't have one and you live in a Hurricane area I highly recommend a 12 to 15 hp portable propane generator No apologies needed there. A. It's excellent info. Please do feel free to always share. B. The figures you're giving can be related to other engine's power usage. Share this post Link to post Share on other sites
Snoopy11 5,714 #16 Posted July 4, 2022 On 7/3/2022 at 11:03 AM, pfrederi said: They do not seem to have special heads.. or they would need premium gasoline Hmm... well... my Duromax 457 started out life as a gen. motor. from model XP10000e... That is a dual fuel generator. I think it was mentioned above that propane is around 110 octane... and burns much hotter than gazzoleen... Having said that, when I started pulling my Duromax apart... the exhaust valve was stainless and it had automotive style retainers with dual spring on exhaust valve. In my humble opinion, this is the minimum for any dual fuel engine. Now, I changed valves and went with my own, but I said all that to say this... If I did a conversion from propane to gazzoleen... I would run as high octane fuel as I could buy... and maybe add racegas concentrate to the mix... My worry is cylinder head temps... and pinging/knocking... particularly if you don't run high enough octane fuel. Other than that, I don't see any problem. Some people don't know.../... care that their engines are knocking... but octane really matters in engines like this, Eric. Here is one more fun fact... HONDA actually recommends for people to use "unleaded gasoline with a pump octane rating of 87 or higher" (lemme know if you want to see the source fa' 'dat)... Most people have no working understanding of engines... so they just go with the cheapest option fuel to get it firing. But hell... what do they care... they'll just go buy another or have it warrantied anyway... Can't do that with custom or performance engines. You have to actually know what the engine NEEDS... not just what best suits your pocketbook... We here on the funny farm run premium fuel in every engine here. I run race fuel in my racing engines. If I go down to 87... I audibly hear a difference in the valvetrains of my engines. Don 2 Share this post Link to post Share on other sites
