So from what I can figure I think I'd really like propane as a fuel in my currently gas fueled carburated truck. The questions are big though and many answers online vague.

The biggest is fuel economy, sure theoretically it's about 10% less cause propane has about 10% less BTUs, and theoretically you can push your engine more cause it's 108 octane. But this assumes you utilize it well. And that comes down to the system/carb used and how well it's tuned.

What I really need is details on how propane carbs generally work, how they are tuned, if some are better then others etc.

My engine currently uses a square bore carb. I'm thinking of I can find 2 or 4 good side draft propane carbs of the right size and design I could make a spacer/adapter to mount the propane carbs on the side of it with the original gas carb on top so I have the option to use either or both depending on how I set my linkages.

 

at first glance, i see a few challenges you'll need to overcome. first of all, propane likes a higher compression ratio and/or more timing advance, to burn efficiently. in short, i can't think of a quick way to switch back and forth without at least having to reset your timing every time you switch fuels.
also, you'll have to figure out where to mount the propane tank. i would figure that when people switch over, they likely mount the propane tank where the gasoline tank used to be - but that wouldn't work for your plan, so you're stuck taking up a good bit of your bed space.
so at the end of the day, i would say one fuel or the other, not flip a switch and go back and forth in a moment.
note that i haven't tried doing it myself, so don't take my words as the gospel truth, but rather as one who's done some reading on the subject, as well as having a good mechanical background.

 

Got a plan for that, with different carb intakes I can turbo charge the propane carbs and and not the gas carb. That will allow me to fully utilize the advantages of the propane and make more power while keeping the gas carb as backup. I'll tune the timing for the propane and turbo, and that should be ok for the gas without turbo when needed. I'll idle on the propane and keep the gas carb closed up and empty when not in use. so when not in use it's really just a cap for the top of the manifold.

IDK for sure where I'll mount the tank, but there are plenty of options, not worried about that. Likely at first in the bed, then as I am confident of it working out and want to refill not swap tanks replace the front tank or move my exhaust and mount on other frame rail opposite the main tank.

 

Here is some good data. Propane Facts & Comparison Charts

You actually lose 26% of the energy content of gasoline with propane. AKI is 105, so making a dedicated engine at a higher compression ratio is the simple way to go. A turbo that only works on propane and not gasoline sounds like your complicated way to make it dual fuel.

Since "here" doesnt tell me anything about your location, is propane free where you drive? It seems like the payback for this conversion could be very long. Propane is just as expensive as gasoline in CA, so conversion is a guaranteed money loser.

 

That's good info, found that site but not those charts before, I'll have to do some math on that. Including your 26% enegry content figure.

Yes according to those charts there is 26% less BTU's in propane by volume where I can only assume they mean in it's liquid form. But how it's used effects overall engine efficiancy. Like the fact that you can run it at much higher pressures and leaner. Both of which increase efficiancy.

There's nothing simple about making a dedicated higher compression engine to run on propane. Certainly not from a cost or convience perspective. Where a turbo set up can be made rather cheaply with junkyard parts. I got a rather stock annemic 87 460 that could really use some more pep. I've done all I can externally to it and have pushed it to it's limits without pulling at apart. The only way I'm going to get more power or efficency out of it with gasoline is to first change the cam, which would net decent gains, or rebuild the whole thing which isn't even close to doable or cost effective for me right now. Propane has potental though, lower cost, and higher octane with a managable energy density drop. The devil is in the details though.

Propane around here is running $2.50 to $3.00/gal so with propane at $3/gal I pay the same per BTU with gas at $3.78 and can do more with the propane.

 

I'm not an expert on this, but back in the 80's a lot of LPG (propane) conversions were done here in New Zealand because of substantial fuel savings vs gas.......conversions were even govt subsidised, 50% I think. Today, there's not enough cost saving here to justify the swap cost.

Back then, the base conversions had ignition timing set at a happy medium for both LPG & gas - not optimum for either; better systems had a dual-curve ignition which swapped the timing advance automatically, with the fuel selector switch on the dash.
Original carbs were used, but with adaptor & heater units installed.

But today with computerising & EFI, that is all obsolete. And modern dedicated systems are so efficient, that there is little if any performance loss.
IDK about mpg though.
Ford Australia produces factory Falcons/Fairmonts, that are propane dedicated.

One BIG advantage with propane, if you intend keeping the truck long-term, is the benefit to the engine itself......super-clean fuel, extended oil changes, & LONG engine life.

 

I have propane conversion kit for a V8 engine from my father from back in the 80's. All the componets and instructions no tank. $100

 

Im currently running a Dual Fuel 1999 F250 with a 5.4 triton V8 In the UK

Fuel prices here in the UK are unbelivable to friends across the pond and are approximately $8 to $10 per us Gal!!!!

the only cost effective way to run a large engine toy is on Propane (LPG)
it is readily available at service stations on the pump and with the added technology of an app on an I-Phone station locations are easy to find

all our measurements are metric but its easy to see the difference

gas (Petrol) = £1.40 per litre
propane(LPG) = £0.71 per litre

Almost half price, roughly driving sensible im getting

230 miles to £40 of LPG

its an old system you have to switch over manually but i can run on either fuel, and only needs to start on petrol from cold.

the make is Technocarb, not sure where it is from but anybody with information would be appreciated

thanks for looking


John

 

I'm not an expert myself, but I work in the propane industry and just bought a 2002 f250 with a V10 and had just had a propane conversion installed on it . I was getting 9.2 mpg before and my first tank of propane I got 8mpg, keep in mind that since the conversion I have constantly had my foot in it. I've talked with the tech that installed it and as the novelty of it wears off I will probably end up around 8.5 mpg on propane. A few things about the conversion. It is a propane injection system, I have 10 sepperate propane injectors. A computer that works with my factory computer and does not interfere with it at all. I have a tank in the bed and it comes to the engine in liquid and goes through a vaporizer that is similar to the old styles back in the 80's . It starts every morning on gas and when reaches temperature switches automatically to propane. If I choose not to be on propane I simply press a botton and it switches the gasoline injectors on and the propane injectors off. I love it so far and have notice no discernible power differance . The system is a PRINS and was expensive but I will easily recoup the money in less then a year . I am in the propane industry so get it at a very good price. The average person should recoup the cost in around 18 months . There are also ways if room allows where you live to get a bulk tank and have it delivered to your home to save a lot of money on propane as well. I just went 428 miles on 60.00 bucks !

 

Since there is no location in your profile, where are you? LPG prices vary drastically depending upon region.

 

The simplest solution would be to use an Impco Model 300 mixer as it is designed for dual fuel use and adapters to mount on top of your carburetor are still available. As for how they work, there is good explanation in the beginning of the Impco product catalog.

The challenge with dual-fuel is optimizing timing for each fuel now that Dual Curve is out of business.The simplest solution would be to use a propane-specific advance curve if you're going to make it your main fuel. Fully programmable (like MegaJolt Lite) with 2 advance maps is another option.

Using bulk propane from home isn't really an option as you would need a propane dispenser to fill your truck. It's a much better idea to get a motor fuel account with a local propane supplier.

As for whether it's worth it, like jimandmandy suggests, it depends upon fuel prices and how much you drive.

 

x2

I bought a megajolt to run coilpacks on my capri until i get the injection together. still haven't ran it, but seems to be really simple, and you can switch maps with a switch on the dash.

 

Sorry i live in Vancouver Wa . And propane prices do vary drastically here as well, some service stations are as high as 3.95 pg others are as low as 2.29. The good thing about propane is you can negotiate prices sometimes . I think the way motor fuel works is the company ( like chevron or shell ) will dictate to owner of the station the minimum price they may charge and I've heard they only make .04 to .08 cents per gallon . However propane at times is marked up , up to 300% sometimes . You can get a bulk tank at your home to fill yourself without a pump and motor. It is called a " wet leg " and it works by having pressure push the liquid out into the tank your filling, you just have to vent the tank you are filling so the pressure is lower in the tank you are filling. When you have a bulk tank and if you were buying it in place of gasoline you would be buying a pretty good amount and your price would probably be pretty good. We would sell it for around 2.00 per gallon maybe less if you were buying a lot. Most propane companies around here anyways will lease a tank for under a 100.00 per year . Hope this answers some questions for ya .

 

You can get a bulk tank at your home to fill yourself without a pump and motor. It is called a " wet leg " and it works by having pressure push the liquid out into the tank your filling, you just have to vent the tank you are filling so the pressure is lower in the tank you are filling.

You can not do this if it is a liquid injection system like Roush, and your local taxing authority is going to be unhappy with you if they catch you.

Regards

 

My understanding is that propane companies aren't very enthusiastic about installing a wet leg dispenser to a residential tank - liability issues. See Hooking Up a Wet Leg?