I'm rebuilding a propane powered 390 and I'm looking for any ideas on how to increase horsepower without spending obscene amounts of money. Anyone have any suggestions (or links to visit)for this - different heads, intake manifold, crankshaft etc. I've rebuilt engines before, but never strayed far from factory specified parts, so any help on this would be really appreciated. Thanks.

 

To the best of my knowledge the propane 390 is the same engine as a gas 390 except for the propane system and in some cases higher compression pistons. Is this a high mileage engine? How did it wear? I am told that propane is a much cleaner burning fuel and the engines are still clean inside after years of service? I'd be interested to know? Anyway if you want power go for a 390 buildup burning gas.
William in Atlanta

 

I like the idea of propane powered vehicles. As the previous poster said, it is a very clean fuel. It won't dilute or contaminate the motor oil the way gasoline does.

I've heard that you can run the compression up to 11:1 with propane. Propane yields less energy, but it has a higher 'octane' rating than most gasoline. I'd be looking for some small, tight chambered heads to reduce the distance that the flame front in the combustion chamber has to travel to burn the fuel. And to help keep the C/R up. If I recall correctly, propane burns more slowly then gasoline so you don't want an open chambered head or you'll have some pumping losses from having to run big timing advance numbers.

And keep the quench small. I don't think there's a detonaton problem with propane, even with big quench heights, but for combustion efficiency I'd want to keep the quench to a minimum.
Use a 195 thermostat for at least two reasons; lower friction between the pistons and the cylinders, and less heat loss through the heads (compared to lower thermostats).

Question; how do you tune the propane 'carburetor' for the mixture? Seems like an ideal situation for adding an Oxygen sensor to the exhause pipe to help tune the mixture.

Sounds like a fun project.

 

Steve, If I have my info right the BTU rate on the propane is less than pump gas, and that in itself will cause less performance. That is one reason gasahol (sp) doesn't work so well. The first thing you might try is using gasoline to see what improvements occure.
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Thanks for the info William, pcmenten, and John! To be honest, I don't know much about the engine, as I just bought the truck 5 days ago. It is a high mileage engine, and I'm not sure how much wear it has or how clean it is - I haven't had the chance to start on it yet. It was converted to propane about 3 years ago, so I don't know how clean or worn it will be. I know more about gas engines, but the complete system came with the truck, including a four BBl "carb" and intake manifold, so I thought it might be interesting. As for tuning the carb...I have no clue, but the idea of an oxygen sensor has intrigued me - I'll see what I can find out.
Thanks again, Steve.

 

I have a whole bunch of propane power links. I will try to go through them and see if there would be anything useful, or I could just e-mail you the lot of them and let you play with them.

I've wanted to get my 360 off gas and onto propane for a while, but fuel costs here in VA don't seem to justify it. Though I would still love to do it just to be different. From what I've seen the drop in performance can be mitigated with a higher compression ratio, better electronic ignition (with custom propane curve) and computer controls (feedback system working off oxygen sensor). At the very least, an O2 sensor and an A/F meter would help to tune for the best performance.

There's an amazing Jeep out there that has a turboed V8 running propane. They got some amazing power out of it. That could be fun to play with, but would get expensive quickly.


Mark

 

I've run propane for several years on my 87 460 crewcab. It has been a love-hate relationship at best. I started with an IMCO 350 carb and soon learned that it would run cheap but not fast (or pull anything either) I then went to an IMCO 450, that helped but it still wouldn't pull anything. I called all the propane conversion people around here and told them that I wasn't satisfied with the performance and was call a goof ball by one of them because I wanted performance out of it. I then called IMCO R&D and talked to them. They said the number by the carb model was the approximated cfm that it would flow. They also said that I needed 2 450s on the 460 to get any performance out of it. I had to build my own adapter to get that done because they didn't have one designed. I did that and then found out that I needed 2 fuel regulators to run both carbs. I did that and had a 460 that would run and pull like a gas burner. Propane sell for about 92 cents a gallon here (Texas) but you have to buy a permit to run it. It is based on how many miles you will drive a year and runs $168 per year for 20,000 and up miles per year. You have to mount a tank, usually in the bed, and that uses up part of your hauling room. It is heavy, so your pickup is heavier. Propane is not always available on the road so you have to keep your dual-fuel capability. An older engine, pre hard valve seats, will burn valves. Your oil will stay a lot cleaner, though. As you can see, it's not all gravy. I'm about ready to pull my system off my 460, I'm tired of fooling with it. Besides that it gets 6 mpg on gas and it's 'only' $1.40 per gallon

 

I've worked with LPG and compressed natural gas engines.
Some with the Impco "mixers" and a couple we converted over to port fuel injection with some massive Bosch fuel injectors and a 150 psi rail pressure. Fun times...

It's true that the compression ratio can be raised with LPG. I think one of ours ran 10:1 without pinging.
If I remember right, there may be even more BTUs per pound of LPG (I'd better look that up to make sure), but since it enters as a gas and not as a liquid like gasoline does, the gaseous fuel "crowds out" the air charge. That cuts the peak power by 5 or 10%. You can get back the power with a turbo or supercharger since the anti-knock rating is so high.

Sounds like a neat system.

Please keep us posted.

--Matt

 

>Steve, If I have my info right the BTU rate on the propane
>is less than pump gas, and that in itself will cause less
>performance. That is one reason gasahol (sp) doesn't work so
>well. The first thing you might try is using gasoline to see
>what improvements occure.
>http://www.clubfte.com/users/jowilker/USFlag.gif
>John
>
>jowilker email me
>[link:www.ford-trucks.com/users/jowilker|My Club FTE Page]
>Member since 01 01
>
>[link:www.ford-trucks.net/users/jowilker/NCFTE.html|NCFTO]
>North Carolina Ford Truck Owners Group
>
>In the cool still quiet of night, you can hear chevies
>rusting away.


S250,

I have been running my fords on propane for almost 20 years.

Look at your oil on your dip stick. Unless he has just run it forever
without changing the oil it should be clean. I can get 6,000 miles
between oil changes with propane.

Are you going to run just propane or have a duel fuel set up. I don't run dedicated propane, because I forget to fill up and run out. All I have to do is switch to gas and go get more propane.

Running on propane all the time is hard on your carb gaskets. It dries them out. It helps to run on propane at least twice a week to help keep them soft and plyable.

I like running on propane because where I live it is .40 cents cheaper than gasoline. It runs good, it idles good,...
You can get your horse power up by tweeking your regulator. Anyone who wants more info on that can email me at
diferant@cctc.net
You have to be careful though, it can make it back fire and start a fire..

Hope this helps.

Peyton

 

i hate to mention this on this site but it goes with the question. a few years ago i built a stroked 327 in a 67 chevelle. i ran only propane. on the dyno it was 413hp i ran 13to1 highdome pistons with 202 camel backs. the octane raiting on propane was 128+. the only problem with the propane was the winter out here in utah. hard to start. my buddys oldman owned a propane company so he helped set it up right. when you run the duel fuel its very difficult to find a happy medium for the performance side of the engine.




1966 F-100 4x4 352
4 inch lift with 33x12.5x15 with custom dana 44's front and rear