Propane powered big blocks

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Aug 31, 1999 | 01:34 PM

patsplace

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From: Powell River, B.C.

Propane powered big blocks

I have been told that if a big block is rebuilt to 12.5 to 1 compression for propane that the mileage is about the same (In my part of the world propane costs about 1/2 the price of gas) and that there is not a noticeable decrease in power. I have also been told that by putting an overdrive unit between the transmission and the transfer case ('79 F-250 4X4) that it is possilbe to end up with a driving cost of approx. 25 to 30 mpg. (Keeping in mind the 1/2 price difference in propane Vs. gasoline)
Am I getting the straight goods or is this a big block running for cheap fantasy?
Pat Patrick

Aug 31, 1999 | 03:01 PM

Marty

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Propane powered big blocks

I have been around quite a few propane conversions. None of the owners were very satisfied with the results. A '90 Dodge with a propane conversion (still could run on gas too) lost alot of power and mileage (but that's a Dodge for you). A friend had a '79 Chevy 1 ton with a 400 that was built with propane in mind and it was a dog on it, but switch to gas and it had ample power. The best I've seen is a '72 F250 4x4 390 with straight propane (set up for only propane, no gas), with the engine rebuilt for optimum performance on propane, but my '73 390 (gas) would out perform it anytime. Major draw back of this is he couldn't take it on long trips because propane isn't as easy to come by as gas is.

All of these trucks got worse mpg. But with the propane so much cheaper it ended up costing VERY close to staying with gas ($ per mile). The guy with the Dodge said it took several years for the conversion to pay for itself. But they all lost power too.

just my 2 cents.

Aug 31, 1999 | 07:19 PM

Fordman

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Propane powered big blocks

First of all dont run dual fuel!! It is incredibly hard to time an engine when you are switching from gas to propane and vice versa. Propane can run engines that are putting out some big horses. My neighbor run a 460 on propane and he pulls all sorts off stuff with it. But he does have flat top pistons, a pretty big cam and other goodies. The exhuast sounds great too. He runs 3'' stacks on his 1 ton dually and makes it sound awesome. Mileage really doesnt suffer as others have told you. It runs about the same. My dads 390 on propane got great mileage and had good power too. Get an IMPCO carb and have it tuned good and you are on your way to cheaper fuel and a thicker wallet. Good luck.

Fordman

Aug 31, 1999 | 08:23 PM

Pat Patrick

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Propane powered big blocks

Thanks Fordman,
I've got a pal that has been running his F250 4X4 on propane for 10 years and is currently running it through a CJ and there seems to be no lack of power and he is getting about 10 miles on a Cdn. gal. (1/5 more than US I think.
Have you heard of the overdrive units that go on the shaft between the trans and transfer case. I've heard that with one of those and propane, CHEAP highway hauling and the joy of BIG BLOCK Fords lumping away.
Thanks again
Pat Patrick

Aug 31, 1999 | 09:20 PM

Fordman

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Propane powered big blocks

There are some units that can be mounted between the tranny and the transfer case but you are going to a lot of trouble for that. You have to move the transfer case back to make the OD unit fit in and that means possibly shortening your main drive shaft and lenghting your front one. I have seen people put "splitters" in pickups just like what you see in bigger trucks with 5spd&2sp or 4spd&2spd. These are usually cheaper than a new unit but require the same amount of work. If you have the energy and paitents to put a OD unit in go for it. It is just one more way to make your pickup more unique and more fun to drive. Have fun

Fordman