I bought a 94 F250 4x4 retired USFS truck a few weeks ago. It has a 351 with an E4OD that has a suspect torque converter in it. I have put an 8' flatbed and dually rear on it so far. I also picked up an 1983 460 with that I am contemplating converting to propane or dual fuel (learning about this here) I am all ears. 1GR

 

Payback depends on how much propane costs in your area and how many miles per year you are going to drive it. This sounds a little like a toy rather than business daily driver, so the answer would be no in that case. Also, that E4OD is likely to need more than just a torque converter once the shop opens it up. Be sure to budget for that. Does the 460 have a matching tranny?

 

The 460 came with a 2WD C6, I am thinking of just going all out and putting a ZF5 behind it. It is not a daily driver but, a part time work truck. I am not in the least impressed by fuel mileage of the 5.8. I see reading some of the past threads that you seem to be "the guy" around here on this. Can you tell me what is involved in going dual fuel rather than straight conversion? 1GR

 

Im not the one. Dedicated factory CNG is my experience. I think some of our Canadian members may have a lot of experience with LPG conversions.

 

Your trucks are very straightforward to convert to LPG but jimandmandy makes a good point about the economics of a conversion. Even though your fuel economy might be poor, a propane conversion could take a very long time to payback if you don't drive it very much. Before you do anything else, you should first find out if there is a readily available supply of low-cost propane nearby.

Your 1983 with the 460 would probably work best with an dual-fuel Impco 425 system. Dual Curve used to make a LPG/CNG feedback controller (PN 5952) but Autotronics has shut them down so Dual Curve products are pretty much only available on eBay now. Dual Curve 40622 could have also been used to optimize timing but is no longer available. I have a LPG Feedback Controller and I'm in the working on finding a suitable LPG timing controller.

Your 1994 F250 5.8L would have also used an Impco 425 mixer as well but would also required the Dual Curve 5908 controller, which is now obsolete. Technocarb makes KIT-DP-FO58-87-97 for your truck, which is a complete underhood system and works similarly. Since your truck is MPEFI, you could also use the ESIP parts package. However, the ESIP package only controls fuel delivery. The Cobra timing processor would have to be used for dual advance timing.

 

The good..
propane burns very clean and because of this the engines last longer (typically)
The bad...
Propane gets less mpg, the cost is slightly higher
While the tanks are bullet-proof (literally), the lines and valves are not, in the event of an accident or a exposure to fire occurrs there are 2 types of tank failures that can occur, BLEVE (boiling liquid expanding vapor explosion) or implosion. Bleve occurs when the liquid is converted to vapor and the psi exceeds the tanks design causing a breach; An imposion occurs when the product inside the tank has in essence boiled off and the atmospheric pressure inside the tank is less than the regaular atmosphere, the tank actually again tears apart but collapsing upon itself. The results are similiar for our discussion purposes here....

It basically becomes a missile capable of traveling no less than 1/2 mile (small vehicle size tanks) with enough force to penetrate a 6" steel reinforced concrete wall, not to mention the fire that is created as a result of the highly pressurized vapor being projected at the point of failure....the friction of the escaping vapor rubbing up against the failed material, is more than enough to create a static charge which acts as the ignition source (same a a piezo igniter on a gas BBQ).

 

Are you actually referring to automotive propane system that meet NFPA 58? Even if the fuel line fails in an automotive system, the excess flow valve will prevent an uncontrolled release of propane. In a vehicle fire, the safety relief valve is designed to prevent explosions with controlled blow-offs. Never put fuel into a propane conversion until it has been inspected and complies with the LPG installation code in your jurisdiction.

Since propane only has 74% of the energy of a gallon of gasoline, it will obviously get lower fuel economy but a propane vehicle typically gets better fuel economy than the energy comparison would predict. Old-style mixer systems typically get 75-80% of a vehicle's fuel economy. Modern injection conversions easily get over 80%. If you are buying propane for less than 74% of the price of gasoline (easily done), your cost per mile (or km) will be lower.

YouTube - LPG Car Fire Tests

 

The video clearly displays the point, even with compliance with NFPA 58, a person incapacitated inside a propane fueled vehicle still has a significant opportunity (as compared to a conventional fueled vehicle) of sustaining life threatening burns. In the US, NFPA 58 is a voluntary standard of which the main oems do comply with but there is no requirement for a local retrofitter to comply, only validate their design meets the intent. Thats why anyone can go down and purchase a propane tank for their diesel pick-up and boost the hp....and there is no way that hanging a tank on the outer frame rail with a piece of 3/4" soft, flat steel, is safe, nor is the hose location and valves even close to being protected.

While the NFPA 58 standard does help prevent bleves/implosions, it does not provide for external vehicle impingement protection or adequate crush protection, additionally, most emergency response agencies at best provide training for emergency procedures on these vehicles annually (state & fed osha), but for the most part, as in calif, a basic fire fighter must have at minimum 241 hours of annual training......heck, they don't even work that many daylight hours....In LA, the training is conducted quarterly.....so, for 4 times a year the crews go play at the tower (drill center) and are supose to be certfied in fire/rescue for public assemblies (theaters/stadiums, arenas), businesses, camps, domitories, educational, hazardous material/waste storage & processing & transportation, hospitals, instiutuions (jails, prisons, mental hospitals), merchantile (malls), storage & service (gas stations) facilities, utility, highrise, lowrise, confine space, aircraft (both general aviation, commercial and military), mass casuality, evidence preservation, hazardous material response/recognition defensive tactics/operations, emergency decontamination procedures for emergency response personnel and victims, Weapons of mass destruction recognition & safety, drug lab recognition & safety, radiation responder protective action recognition, monitoring & safety, vehicle rescue (passenger/commerical/buses/military/heavy cargo) including high & low pressure hydrogen systems, electric (high voltage), propane, LPG, structural utility safety and shutdown procedures............. just to name a few...

The reality...
1. The propane systems (even NFPA 58 compliant )are well designed but carry with them an increase inherient risk not only to passengers but to other external of the vehicle even in the most mundane, controlled situations.
2. Few of our response personnel recieve initial let alone adequate refresher training.

 

[QUOTE=Beechkid;10187837]
BLEVE (boiling liquid expanding vapor explosion) or implosion. Bleve occurs when the liquid is converted to vapor and the psi exceeds the tanks design causing a breach; An imposion occurs when the product inside the tank has in essence boiled off and the atmospheric pressure inside the tank is less than the regaular atmosphere, the tank actually again tears apart but collapsing upon itself.

CORRECTION A BLEVE occurs when the tank surface is weakened by direct flame impingement and the tank itself fails at that point due to pressure in the tank there have been numerous times where a tank has been involved in a fire and not bleve'd because A there was not direct flame inpingement or B the first responders have keep the tank surface cool with hose spray. The relief valves in the tank are designed to release pressure at 250psi for a standard domestic tank and 312 psi for most over the road motorfuel tanks, the safety margin on a asme domestic tank is 4 to 1 or 1000psi. DOT tanks are similar. I have never in 35 years seen a lp tank implode.

Regards

 

[QUOTE=gasman6674;10188539]A blevel does not occur as a result of direct flame impingement but the result of fatigue caused by 1. Internal pressure, secondary causes include direct flame impingement which can cause the container to fatigue. Application of water must occur within 10 minutes of areas in direct impingment with a minimum flow of 500 gpm per area (both referenced in NFPA, CFSTES and DOT standards), with the primar purpose being to cool the tank and reduce the psi which reduces the internal temps (Boyles Theory). The size of the BLEVE is dependent upon how much remaining liquid vaporizes when the container fails (NFPA Fire Protection Handbook 3-39).

With regards to implosion, you're right, they are very rare in occurance.

I appreciate your industry input.

In calif, the hydrogen industry funded the development of an emergency response course specifically for fire fighters and the solar industry has an emergency response course as well (since those panels are also "loaded with inherient hazards)- there are national programs as well- a primary point to this issue, we can have all the greates training programs in the world, but if no-one gets the training or gets the annual refresher training what good is it....visit your local fire station, ask when they last had specific training on any of these-

 

You guys have been busy while I was away buying a truck with a propane system in it.

 

1GR, it looks you got yourself an Impco dual fuel CNG system. You have a Model 300 mixer but I can't tell if it's the 348 CFM version or the 432 CFM version. The Model 425 mixer I suggested earlier is rated at 460 CFM @ 1.5" Hg.

Assuming an 85% volumetric efficiency, your 460 engine should flow 348 CFM @ 3076 RPM, 432 CFM @ 3818 RPM, and 460 CFM @ 4066 RPM. The flow rating doesn't mean the engine won't rev higher, it just means that the gas valve that regulates gas flow tops out at these RPMs. Once you reach the rated flow of a gas-valve mixer, the fuel mixture will become progressively leaner. Lean fuel mixtures are OK with gaseous fuels but you will notice a definite decrease in power at higher RPMs.

If you want to use these parts for LPG, only the mixer and VFF30 fuel lock will be useful. The Model PEV-1 regulator doesn't have an integral heat exchanger and provides positive pressure to the mixer (LPG requires negative). If you have a CNG station nearby, you might want to consider a CNG conversion instead now that you have the parts.

Does your truck still have the CNG cylinder(s)? If so, what is the expiry date?

 

I think the video more clearly shows that you will die if you remain inside of a burning vehicle, regardless of which fuel is on-board. I just trying to show with the video reference that a propane motor fuel tank does not become a missile launched from a burning vehicle and that it doesn't readily explode.

From your posts, I suspect that you have a firefighting background and I appreciate your concern for safety. I agree that many people (like the diesel-propane DIYers) do not try to comply with NFPA 58 but that isn't a reason to ban properly-done fuel conversions. Propane (and CNG) conversions have an excellent safety record as noted by gasman6674. My guess is that you're thinking of propane depot fires (like the Sunrise Propane fire in Toronto) wrt to missiles and these types of incidents show what happens when regulations are not followed.

I think firefighters respond to a lot more electrical fires due to faulty wiring than to propane vehicle fires. If you're going to ban propane systems with a broad brush, you might as well also ban all electrical wiring in homes because some people ignore the National Electrical Code (NFPA 70).

 

You are right, 30+ years in Public Safety, conducting threat assessments, management plans at local, state federal & DHS. Amoungst my credentials includes an Instructor for the State's hydrogen highway safety group (vehicle response & safety)

 

The truck I was going to put the carbed 460 in currently has an EFI 351. I was under the understanding the LPG conversions didn't work on EFI, I guess it does, seeing how it is hooked up on the 300/6. What would the calcs be for the 351? It is currently a little under powered on gas with the loads I am hauling. I was reading somewhere that people were able to switch between the the two fuels and I thought of it for running it down the highway after I got up to speed if it is that much under-powered.

I am currently getting about 8.5 - 9ish MPG empty with my trailer. I did not check it loaded yet. Gas here is currently $3.80+ and LPG $1.89.

It did not come with a tank. I am sure I could round them up. I have plenty of room to run it/them as a saddle tank(s) under the sides of my flatbed. They would be exposed to side impact, but I have a bit of a deathwish anyway.