While I'm at it, how about changing from gas to propane or compressed natural gas? I'm doing a ground up restoration, and I have a 4.3, a 327, and a 350 to choose from, and I have a chevy 5 speed (1st is a granny gear). Please refer this to my question about 2 speed rear ends, as well. Thanks for your input.
About propane/CNG...
- Thread starter qonos
- Start date
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
propane will work well on any combustion engine. tuning specific setups also exist to optimize the use of cng or propane. i had a impco mixer and regulator on my 85 chevy 3/4t worked well on any angle and always idles well. you will lose some acceleration with propane vs gas. but won't need a two speed rear diff like a dump truck diff or something would have. do a search on propane facts and vehicles i learned alot.I have been out of the propane loop cause i'm diesel injected now. 
Friendly Persuasion
Big Plans Tiny Budget
My experience with alternative fuels.
If you are thinking of converting to Propane to save money, give it a second thought. You burn more propane to do the same amount of work as compared to Gasoline. The cost of propane needs to be a 50% of the cost of Gasoline for you to break even.
When totaking the cost of running your veicle on propane into any calculation you need to consider a few things. The cost of the components to convert to LPG, the cost of the anual inspection that is required by most insurance companies, provincial or state vehicle registries all needs to be added to the cost of fuel to do a true comparison.
Not the mention the added inconvience to finding a fueling station not all gas station sell propane. In fact more stations sell diesel than sell propane. I found that every trip became a hunt for a station to by fuel. This is even more of an issue with CNG.
You also need to consider that propane burns a lot hotter. You will find that this is amplified if the system is set up to run rich. This will result in the exhaust valves and valve seats wearing prematurely.
This has been my experience.
I hope you will consider all your options and seriously think about this before making any decisions.
I think you would be better of going with gasoline fuel injection.
If you are thinking of converting to Propane to save money, give it a second thought. You burn more propane to do the same amount of work as compared to Gasoline. The cost of propane needs to be a 50% of the cost of Gasoline for you to break even.
When totaking the cost of running your veicle on propane into any calculation you need to consider a few things. The cost of the components to convert to LPG, the cost of the anual inspection that is required by most insurance companies, provincial or state vehicle registries all needs to be added to the cost of fuel to do a true comparison.
Not the mention the added inconvience to finding a fueling station not all gas station sell propane. In fact more stations sell diesel than sell propane. I found that every trip became a hunt for a station to by fuel. This is even more of an issue with CNG.
You also need to consider that propane burns a lot hotter. You will find that this is amplified if the system is set up to run rich. This will result in the exhaust valves and valve seats wearing prematurely.
This has been my experience.
I hope you will consider all your options and seriously think about this before making any decisions.
I think you would be better of going with gasoline fuel injection.
If you have a modern engine your valves and valve seats are made of very hard metal and I would imagine that they wouldn't wear. Also the nice thing with cng is that a) you can have a refueling station in your house and b) you can run on either CNG or gas. So use CNG to do your daily driving around the area and gas when you go on long trips.
you make some valid points about propane. a specific build would be the only way i went back to it. had it for awhile and with the price now there is no incentive to use lpg. I would use cng if it was available and a cheaper conversion.sooooo diesel is the way if you think about it.....more air/fuel=more power....my 3b without the turbo has more torque than most stock early v8's with 1/4 of the fuel used....
zuluzeugma
SILVER Star
1. Review your organic chem. Propane is only 10% less energy dense that gasoline
2. If your engine ran hotter because of propane, you did something VERY VERY wrong. I've experienced temps. 20-30 degrees cooler. If youre circulating coolant around your regulator, it functions as a heat exchanger and cools your water even more.
3. True story about filling stations... However, if you plan ahead, you can do just fine.
4. Read my build up: https://forum.ih8mud.com/40-55-series-tech/246504-propane-report-trip-1-a.html
Friendly Persuasion
Big Plans Tiny Budget
I understand your organic chem that is one of the reasons that I purchased a propane vehicle when I bought my first LPG truck. I then perform some more research. Propane causes approximately 4 % power loss (which is the ratio of the volume of fuel to the volume of fuel / air mixture) compared with only the value of % 1.72 with gasoline powered engine. Introduction of gaseous fuels in the intake manifold decreases the air partial pressure notably compared to gasoline. This reduction in power is inherent the structure of gaseous fuels. This is further compounded by the relationship of "heat of vapourization" which simple put means that the intake air temp is lower in a gasoline engine because the gasoline consumes heat when it vapourizes. One of the reason LPG burns hotter is because the charge air is not cool by the fuel vapourization. The average amount of heat energy lost by the cooling system vapourizing the fuel does not compensate for the temperature rising in the combustion system. This is not as visible in the FJ40 due to the oversized cooling system but in a vehicle with a much closer matched cooling system you will see the temperature increase.
I set my LPG systems up using a 5 gas analyzer. I tried multiple different mixers and was never truely satisfied.
There was a comment regarding newer engines having harder seat and valves. This may be true however the 1990 Bronco 302 I had on LPG still managed to milled the exhaust valves into the head.
I am a believer that LPG can run well and can be more effiecent. Through my experience I am convinced that the only truly consistance and effective way to run LPG is build a high compression engine and the LPG must be liquid injected. Unfortunately this technology is still so over priced that it does not make for a cheap economical install.
Again the comments above are based on multiple years of personal and professional experience I do not claim to know everything and that is why I am very careful to make it clear that what I write is my based on my opinion, experience and research.
Gavin
zuluzeugma
SILVER Star
Interesting... Not calling you a liar, but you can find 50 people on this board that are running pane on 1F's and 2F's. IF you go over to pirate, you can find 200 people running pane on a 20r/22r and a bunch of others running it on a small blocks. I have never read anyone seeing higher operating temps. As mentioned, I noticed engine temps 20-30 degrees cooler than with gasoline. I'm a mechanical engineer so I took thermo and fully understand heat of vaporization. It would seem to me that passing your coolant through a heat exchanger where the low temp sink is below 40 degrees F would more than compensate for the lack of phase change in your fuel medium. I definitely agree that high compression is the way to go with propane to take full advantage of the higher octane rating.
Someday, when the material catches up with the theory, there will be propane engines running on the diesel cycle. It would take some pretty strong head bolts (studs) to put up to 30:1 compression ratios...
Friendly Persuasion
Big Plans Tiny Budget
At least there are a few things we will agree on.
Have you had the opportunity to look into liquid injected propane? Chrysler had a few vehicles, vans mostly, running with a system developed by a university in the US that were performing very well. The draw back is that the high pressure pumps in the tank required to keep the system under enough pressure to remain liquid failed too often. Then what do you do with a tank of propane that you cannot burn in an engine that requires higher than tank/line pressure to run?
I agree some day in the not to distant future they may design an economical engine from the ground up to run on propane and utilize all of the benefits that LPG has to offer whether that will be a vapor system or a liquid system has yet to be determined. The gap between what is theoretically possible and what is practically achievable is getting closer everyday.
zuluzeugma
SILVER Star
Yeah, I read through their whole report on converting that chrysler mini-van... It was pretty neat. Still confused on higher engine temps, but either way, PROPANE RUNS UPSIDE DOWN!!! and that was a lot of the reason I did it. I was getting in off-camber situations where my carb was starving out. Fuel injection does the same thing but that needs wires and a computer...
Good conversation...
Explain please.
All my pane lines run liquid.
And, Pane running hot is something I have never experienced or even heard of.
BTW, 1990 302 heads are not exactly the best heads out on the market.. Pretty crappy heads actually.
I have been running my 40 on pane for almost 8 years now. Nothin but pleased.
Friendly Persuasion
Big Plans Tiny Budget
The reason the liquid injected propane requires a pump is that the fuel pressure needed to be raised as it was vapourizing in the fuel lines and in the comon rail feeding the injectors due to the heat of the engine and the engine compartment.
I only brought up the 302 to relate to the JoeyG1973's comment regarding newer engines not wearing.
I am glad to hear you have had great experience.
I recently had the opportunity to dicuss CNG with a Ford Service Director. Ford offered GNC vehicles until 2004. He still services a fleet used at the airport. His first hand testimony is the engines are immaculate....5000 mile oil changes the oil looks brand new. They had the occasion to tear down a GNC engine and there was zero carbon build up, engine parts looked brand new. The only draw back he stated was the tank location / capacity.
Here is a company that makes some nice electronically controlled Propane systems.
Raso Enterprises Auto Parts
From what I have read especially with the electronic propane system there is almost no loss in power and fuel mileage. This is due to the gaseous (LPG) delivery of the fuel being more efficient than the liquid delivery of gasoline (from what they say). Don't know if it is true but people I have talked to with propane cars say they get excellant mileage. I'd like to try the duel fuel on my old 390 in my F-250, with the high compression it would love that high octane.
On another note there are diesel engines that run on LPG. Toyota in the Dyna's and Toyoace's offered 14b's and 15b's in LPG form.
Raso Enterprises Auto Parts
From what I have read especially with the electronic propane system there is almost no loss in power and fuel mileage. This is due to the gaseous (LPG) delivery of the fuel being more efficient than the liquid delivery of gasoline (from what they say). Don't know if it is true but people I have talked to with propane cars say they get excellant mileage. I'd like to try the duel fuel on my old 390 in my F-250, with the high compression it would love that high octane.
On another note there are diesel engines that run on LPG. Toyota in the Dyna's and Toyoace's offered 14b's and 15b's in LPG form.
On my 40 I've found that propane gives around 90% mileage compared to petrol. Since I've increased the compression to use it better they run about equal.
And I've never had heat issues.
I've also run a number of vehicles on CNG but it does have a much poorer milage ratio to petrol.
A freind is a certified installer for direct lpg injection and has only had very positive results with it so far.
If I could get the cash to gether I'd love to try it myself. About 20% power improvemnt because it can be fully mapped by an ECU.
And I've never had heat issues.
I've also run a number of vehicles on CNG but it does have a much poorer milage ratio to petrol.
A freind is a certified installer for direct lpg injection and has only had very positive results with it so far.
If I could get the cash to gether I'd love to try it myself. About 20% power improvemnt because it can be fully mapped by an ECU.
I just put a 73 F motor head on my 79 2f that was completely rebuilt and had .06" shaved off of it. I'll report back on my findings with the increased compression 
