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Jul 21st, 2025 | | | | Joined: May 2012 Posts: 574 'Bolter | | 'Bolter Joined: May 2012 Posts: 574 | hey guys, back in october i found a 58 apache swb stepside pickup and bought it for $250, (and have it sold for $1300  ) the apache has a propane system on it that I am contemplating on installing on my 69 gmc, everything seems to fit flawlessly (surprisingly) but i wondered if anyone has set one of these v6 engines to propane. if so, is it a good setup for a v6, any complaints with it...ETC. all thoughts,comments and suggestions(good or bad) are welcome Indy 
1949 Dodge Coronet 1955 2nd Chevy 4400 1.5 ton 1955 2nd Chevy 3100 1/2 ton 1955 2nd Chevy 3100 1/2 ton 1957 Chevy 5400 LCF 2 ton 1966 Dodge D100 Sweptline 1968 Chevy P20 stepvan 1969 GMC LWB pickup 1972 GMC Sprint 1974 CP30 shorty bus There are three things that I've learned never discuss with people: religion, politics, and the Great Pumpkin.----Linus Van Pelt Trying to understand the behavior of some people is like trying to smell the color 9  | | | | | Joined: Feb 2004 Posts: 28,674 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 28,674 | Back in the late 1970's I maintained a fleet of vehicles that ran on Propane. No GMC V6's in the bunch but a wide variety of other engines. You'll definitely need hard exhaust valve seats, as LP is a "dry" fuel which is very hard on seats. It's also 110 octane, so you can advance the ignition timing way beyond what's used on gasoline. If you're using evaporated gas through the throttle body (the most common type of LP system) you'll see a power loss due to the displacement of air by the fuel, usually about 10%-15% with no way to regain it. I have seen some attempts at injecting liquid LP below the throttle plates, but then there's a major problem with cooling the intake manifold due to evaporation that can build up a huge amount of ice inside and outside of the manifold runners.
Propane systems are interesting but there's a LOT of gremlins to deal with.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
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| | | | | Joined: Nov 2002 Posts: 2,715 Carburetion specialist | | Carburetion specialist Joined: Nov 2002 Posts: 2,715 | Don't know where you live, but the state of Missouri has a extra propane license (in addition to the normal license plate fee) if you have propane on your vehicle WHETHER YOU USE IT OR NOT! This fee used to be an extra $110. per year, don't know what it is now. Additionally, expect to pay state and federal road taxes on the propane when you buy it. You cannot fill the propane tank on the vehicle without the propane license.
Also, propane has 91,000 BTU/gallon, as opposed to gasoline at 117,600 BTU/gallon. Your fuel economy will drop.
Jon.
Good carburetion is fuelish hot airThe most expensive carburetor is the wrong one you attempt to modify. If you truly believe "one size fits all," try walking a mile in your spouse's shoes!The Carburetor Shop | | | | | Joined: May 2012 Posts: 574 'Bolter | | 'Bolter Joined: May 2012 Posts: 574 | forgot to mention a possible important detail..... it is a dual system, meaning it has a gasoline to propane switch under the dash. I don't plan on running it on propane constantly, but just when I'm low on gasoline and need to get to the gas station, etc... Indy
1949 Dodge Coronet 1955 2nd Chevy 4400 1.5 ton 1955 2nd Chevy 3100 1/2 ton 1955 2nd Chevy 3100 1/2 ton 1957 Chevy 5400 LCF 2 ton 1966 Dodge D100 Sweptline 1968 Chevy P20 stepvan 1969 GMC LWB pickup 1972 GMC Sprint 1974 CP30 shorty bus There are three things that I've learned never discuss with people: religion, politics, and the Great Pumpkin.----Linus Van Pelt Trying to understand the behavior of some people is like trying to smell the color 9 | | | | | Joined: Nov 2006 Posts: 2,544 Shop Shark | | Shop Shark Joined: Nov 2006 Posts: 2,544 | Lots of stuff to maintain for just a backup system.
| | | | | Joined: May 2012 Posts: 574 'Bolter | | 'Bolter Joined: May 2012 Posts: 574 | so I would probably be best to forget the propane system? Indy
1949 Dodge Coronet 1955 2nd Chevy 4400 1.5 ton 1955 2nd Chevy 3100 1/2 ton 1955 2nd Chevy 3100 1/2 ton 1957 Chevy 5400 LCF 2 ton 1966 Dodge D100 Sweptline 1968 Chevy P20 stepvan 1969 GMC LWB pickup 1972 GMC Sprint 1974 CP30 shorty bus There are three things that I've learned never discuss with people: religion, politics, and the Great Pumpkin.----Linus Van Pelt Trying to understand the behavior of some people is like trying to smell the color 9 | | | | | Joined: Jan 2008 Posts: 4,903 'Bolter | | 'Bolter Joined: Jan 2008 Posts: 4,903 | A local LP distributor ran his delivery trucks on propane from the 50's until about 25 years ago. His delivery trucks are no Diesel. I think that says something for LP. I have 2 forklifts on propane. It is good for forklifts because they always start and propane doesn't go stale like E10.
Texas as well as Oklahoma require an annual prepaid users tax stamp. I wouldn't consider propane on the highway any more. | | | | | Joined: Mar 2012 Posts: 211 'Bolter | | 'Bolter Joined: Mar 2012 Posts: 211 | I saw a propane powered GMC v6 1 time in a junkyard the thing looks huge not sure of the size but it was painted yellow in color probably also came from some sort of big forklift I was tempted to buy it just to play with it but I ask myself why? | | | | | Joined: Feb 2000 Posts: 4,886 'Bolter | | 'Bolter Joined: Feb 2000 Posts: 4,886 | The road tax for natural gas we use in our school bus fleet is $75 per bus per year in Missouri. Up the road from us, a beer distributor uses propane along with diesel on there fleet of trucks, its a fogging system that just dumps into the intake. Works by adding more propane the faster you go, no metering or throttle bodies, they really like the way it works.
Joe | | | | | Joined: Dec 2014 Posts: 55 Wrench Fetcher | | Wrench Fetcher Joined: Dec 2014 Posts: 55 | My 65 c60 came with a big old propane tank feeding the little ol 350 in it,the gauge still shows about 1/2 tank. So Im going to either have to burn it up driving it around ,or park the truck in my back yard and hook my gas grille up to the side of the truck and use it up that way!  If it ever gets warm enough more me to go back out to the barn and start working on the spunky little retro 427 I want to build for it,Ill have more motivation to start working on the truck again. We threw together a zz502 clone a while back with iron rect port heads that I thought about throwing in there for a couple weeks just to see how many kids I could freak out in mustangs with a 550-575ish horse roller cammed rat,but then I thought those old junky [censored] drum brakes and decided against it. The propane conversion stuff from this truch will be free good to a good home once the engine swap is done though.
Last edited by zmaxmotorsports; 01/01/2015 12:00 AM.
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