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Has anyone ever pondedred a propane system on a 4.2 liter???? I've tried many searches on the net and haven't found any decent results.:( With the price of gas and the price of converting to fuel injection to get rid of the carb, I thought propane would be a interesting alternative (and no I don't want a V-8:clown) . As well the loss of power with the conversion would not be a concern as the engine will be getting a rebuild at the same time.

So has anyone ever seen or thought about it....am I on glue:*******

Greg
 

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I know I've seen a write-up on this, from a guy in Europe who did an LPG conversion on his 4.2L. Of course I can't find it now...

I think the mechanics of the conversion are pretty much the same as for any other engine. You'd probably want to get the head rebuilt with propane valve seats, and then it's just a matter of getting tanks, mixer, and all the other propane stuff.

AFAIK, it's technically illegal for untrained howler monkeys (ie: the general public) to install or service this stuff. Not that this stops most people, but just so you know...

I'd suggest making some phone calls to conversion places locally, to get an idea of what's involved.

Chris
 

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GWG
I think I have the same bottle of glue!

Was thinking of putting propane on my 4.2 as well. I've run propane on a few vehicles before and am a fan of gas in a bottle.

The part that is convincing me is the ability to run off camber with no ill affects like the old Carter stumble and stall. Propane will run upside down even (glad I wasn't the test unit for that)

The economy is also bonus but here's a couple things to keep in mind

Mileage drop, more so on the highway than in town. Propane has less BTU content than gas. so you use more qty of propane for the same power as gas. about 10-15% avg.

No accel pump in propane systems, may seem a littleslow to pickup when you mat it as compared to gas

Storage Especially in a CJ5 or 7 hard to shoehorn a large tank inbetween narrow frame rails to get decent range and keep ground clearance (iam tempted tp box off rear seat area and put tank under the seat, has to be sealled from cab area)

May be hard to get fuel in remote areas.
May be hard to find someone to set up properly

Positive side
Spare fuel comes in convient 20lb, 30,lb, 100lb and larger size bottles all you do is use adapter hose invert bottle and hold or set bottle higher than tank. same tank runs barbque 20lb =5gallons

Runs at all angles side to side or front to back no one cares
simple to fix, overhaul kit fits in corner of glove box, installable by 3rd grader if you ever need it.
Likes high compression 10-10.5.1 would be really good, and you are rebuilding anyway, thow in a RV cam and headers
Cheaper than gas, expect to save about 30%at the end of the day at current prices calculating in milage drop blaa blaa
Extra weight in the back(heavy tank) helps balance out the heavy front end, improve handling(If you call it that)= you can get a bigger winch
Spark plugs last 2x as long(Using platinum)
Burns clean


I would check, but may even be aircare exempt, I know people have been having it done and having trouble but the byproducts of combustion are water and carbon DIOxide and thats it I suspext there may be an exemption in the fine print
Engine runs smoother

Cheep to get from junkyard, OHG Or Impco are the simplest and most durable. I would suggets propane only on none fuel injested engines and dual fuel on EFI. Set up for propane only and you can adjust timimg and advance curves for optimal performance(Advance curve is just the springs on the flyweights, simple stuff)

Anyway just my .02, send me an email if you have more questions
 

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OOOHHHH another nasty thought

While your thinking about a rebuild, why not do the Rob Bryce 4.0/4.2 stroker mod that would be excellent on propane, just leave the EFI part out and run straight propane.

(Hope I quoted the right name on the stroker mod)

The write up is or was on this website in the tech section, awesome conversion
 

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Between the cost of adding propane and rebuilding the motor, you could probably pay for a fuel injected V6 or V8 swap.

I think you could get a Chev 4.3 TBI V6 and the adapter you need for under $2000. It would make more power than your 4.2 but not enough to break parts. It would get better mileage than your 4.2 too.

FWIW, I've got under $2000 into my TBI 350 swap and I'll have under $1500 into Lynn's TBI 350 swap. I got a great deal on both motors but anyone could have picked them up for that price.
 
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