OA331 Gasser Conversion to MF

[ems4ty]

Ok... Not sure if this is normal or if there is something wrong. My 53 Reo M35 has a Continental OA331 Gasser. I've replaced the plugs and wires with new, flushed all the fluids, cleaned the Oil Bath Air Filter and connected up all the hoses that the previous owner left hanging around.

My problem is that this truck is gutless! Painfully, gutless. Not sure if its just because its a gasser or what. I can get the truck to maintain 50-55MPH, but my mileage is a ridiculous 4-5 MPG.

Is this just the nature of a gasser motor? Should I consider looking into a engine swap and if so, any recommendations to what motor/setup would drop in its place. I'm not made of money here, but at this rate, I might have garage it for a while...

Thanks for the help,

 

[DDoyle]

Tyler,
I don't know your terrain, but for flat level ground your mileage is bit lower than mine. Since you have a Multifuel already, as you know none of these trucks are rocket ships.

You've probably noticed the gasser is much quieter than the Multifuel.

I've toyed with the idea of coupling an overdrive transmission to the gas engine. Not after increased speed, but for lower RPMs - may help mileage as well. Direct swap, and fairly cheap.

Regards,
David Doyle

 

[ems4ty]

Flat terrain - no problem. Any kind of incline and can't keep it in 5th gear as the motor just doesn't seem to have enough balls to keep it moving. The mileage is what I'm really after though. My brothers 1970 AM General has the MF and seems to do very well. Haven't really driven it much because its not registered yet and has brake problems...

Been toying with the idea of swapping the motor to a MF type but don't really know where to begin or how involved it will be...

 

[clinto]

There is a great thread where Recovry4x4 sort of documented the process of converting his gasser 108 into a MF. If you can't find it, I am sure Kenny will pipe in and provide a link to it

 

[Recovry4x4]

Here it is! http://www.steelsoldiers.com/index.php?name=PNphpBB2&file=viewtopic&t=4163
It's not really a weekend job but not too terribly difficult. Oddly enough, I've always marveled at your truck wishing I had one like it with the gasser. Anything not covered in the thread, I can answer. The swap is still fresh in my head.

 

[OPCOM]

I've been told that a properly running gasser will walk away from a MF, and that they get 6 vs. 8 MPG. No experience there. I guess the things need to be checked like timing, compression, carb rebuild? intaker manifold vacuum leaks, etc.

 

[ems4ty]

Well, Thats what I was kind of wondering, but haven't really seen any specifics on this gasser motor yet. I've done the basics, but will need to check the compression ratio. Haven't got a timing light that will work with these waterproof plug wires. And don't have any parts available for the carb... That's kinda where I'm at right about now.

Recovery, you recall what the ballpark cost is to do the swap? (Motor, Tank, Etc...)

Thanks guys for the help. I'd rather not swap the motor if I didn't have to just because I've invested a bit into it already, and no one else really has a gasser anymore...

 

[DDoyle]

Memphis Equipment will have all the carb parts. What kinda specifics do you want to see? Timing light setup much cheaper than an engine.

Regards,
David

 

[Westech]

you can still get the timing lights that the pick up goes in between the plug wire and the cap.

 

[ems4ty]

What kind of timing light should I look for? Any specific brand/model? I have/had one that would go between as standard plug and normal plug wire.

As for the carb parts, I'll have to see if they have a rebuild kit. Engine runs good already, no excessive ping/knocks. A little rough on idle (Seems to miss every once and a while). Starts up like a champ when cold, but warmed up it takes about 10 seconds of turning over before she decides to run.

 

[BFR]

Re: RE: OA331 Gasser Conversion to MF

I've been told that a properly running gasser will walk away from a MF

I have never heard that before.

on the other hand I have heard that the 6602 gasser found in 5 tons is a torque monster.

 

[cbvet]

RE: Re: RE: OA331 Gasser Conversion to MF

I think our gasser is a little "quicker" than our multi. And a LOT quieter.
Eric
CBVET

 

[Junkyard Wars Crusher]

There exists a small "pigtail" adapter that is placed inline between the spark plug and spark plug wire that allows you to use an ordinary civilian style timing light (with inductive/clamp on style pickup). It is part of a test set kit, but I have one that I purchased individually. I got mine from one of the dealers at the MVPA convention in Dayton last year. I can't remember the dealer name, but they had a large quantity and it was less than $10 (I think) I can get a picture and/or part number later today. If you can't find one, you can borrow mine if you want to pay the round trip shipping.

 

[Barrman]

The issued wire is what you want to end up with.

But, in the mean time, you could just take a regular car spark plug wire, cut off both ends. Strip about 1/4" of insulation away from each end until you just have the black core sticking out. Unscrew the #1 spark plug wire on the OA331 from the distributor cap. Stuff your just made cheater wire into the cap with the core stuck to one side. Now do the same with the other end of the cheater wire into the shielded plug wire. You might need to zip tie the shielded wire to the fuel line just above the distributor to keep it from pulling out.

Get a regular timing light and clamp it to the cheater wire. Get a spare charged 12V battery and plug the timing light power leads to it. Don't try just a battery charger, it might or might not work. Use a battery.

Set timing like anything else now. I don't have my manuals here at work, but I "think" 5 or 6 degrees BTDC is what the spec is. I will look it up tonight if no one else chimes in with the for sure spec.

 

[Recovry4x4]

I have a Simpson timing light that is GI issue. Found it on Ebay a spell ago. It is selectable 12 or 24V and is neatly contained is a gray steel case. Model number is a PTL-3M and NSN is 4910-00-937-5724. Contract number on the case is from 1974. I think I've learned my lesson though. Usually when I sell my gasser stuff or genset stuff, I sell all my spares then end up with another one. I'll keep this light but just like the one member with the steering wheel pulller, it's available for members to use as long as they pick up the shipping dime in both directions. Before that I better make sure it works.

 

[ems4ty]

Right on. I appreciate the help. Hopefully its just a timing issue. Another fellow locally thought a valve adjustment might be in order too... Just didn't know if its normal for this OA331 to get such terrible MPG. I may need to take you up on the timing light, but I'll check around locally first for cost reasons.

Does anyone know if the oil bath air filter is really effeicient or not? I took the pan off of it recently, cleaned the pan, put fresh 30W oil in it to the line and reinstalled. Guess that's all that needs to be really done with it.

 

[jeli]

Re: RE: OA331 Gasser Conversion to MF

I've been told that a properly running gasser will walk away from a MF, and that they get 6 vs. 8 MPG. No experience there. I guess the things need to be checked like timing, compression, carb rebuild? intaker manifold vacuum leaks, etc.

I remember my Dad saying that. He ran gassers in Germany. A multi would take them on the hills but on the flat the gasser would outrun them.

If you aren't particular about the military look I've wondered if a Ford 300 would be a good gasser upgrade? You can get SAE blocks that were used in industrial applications. I'm not a Ford guy myself and would drop my 454 in first but for a no frills straight 6 to straight 6 conversion I bet it would work quite well.

 

[spicergear]

RE: Re: RE: OA331 Gasser Conversion to MF

The little gasser I had in my '53 REO ran real strong...exhaust manifold was cracked to bits though-

Jeli, thank you for posting...I like your avatar.