Farmall M Distillatte Questions

Started rebuilding my 1939 Farmall M some years ago and at the time did not have the proper tools to do a full head restoration. I took it to a guy who redid everything and when he was done told me oh yeah by the way this is a distillate head. Shame on me for not paying attention to that ahead of time as I may have opted to get a gas head instead. Oh well too late it's rebuilt. So now I am going through the process of rebuilding the rest of the engine and noticed it had stepped head pistons in it. These obviously was not the original pistons. I knew the engine had been rebuild as soon as I dropped the oil pan and noticed the rods and caps were not matching. I'm going to take a guess that a novice rebuilt this tractor at one point and didn't really know what they were doing. Anyway I am trying to figure out if I have a gas or distillate manifold. What are the differences I should look for? I assume this was run on gas after the rebuild seeing how it had the stepped pistons and no small starter tank or shutters on the radiator. My guess is they didn't spend the money to upgrade the manifold but I don't know what the differences were to verify this. Going forward I want to run this on gas so I assume the stepped head pistons with gas manifold are the way to go but can anyone verify if just putting this combination in place will result in what would be considered normal M compression and horsepower numbers? If it's going to be a complete dog I might tuck my tail between my legs and start searching for a gas head. Any and all info on the subject would be appreciated. Thanks in advance.

Josh

Distillate fuel had to be heated at intake. These manifolds had an adjustment lever to channel exhaust around the intake pipe to prewarm the intake air. Distillate burners had to be startd and warmed up on gasoline. It is just fine to run these engines on gasoline continueously. I would just operate it as it is and not worry about it. For what its worth, I don't think you can even buy distillate anymore. All these distillate tractors are being ran on gas.

Distilate manifords have a damper in them that was closed somewhat to let the engine run hotter. There was also a metal cover went over the manifold to keep heat in and shutters were closed partially to get the engine up to "Run" which was a hotter range so distillates burned better. You will see the damper if it has a distillate manifold. Many a farmer ran gasoline in their dual fuel tractors after the war and distillate heads ran just fine on gasoline. I see many people talking on here about distillate as a poor man's fuel. Well I have news for them...a distillate designed tractor had all kinds of power running on kerosene. My Dad would switch from gas to kerosene to do the plowing,he put the shield over the manifold,closed the shutters until the heat guage was in the right range and he said that old M would pull like a trooper and had all kinds of power with kerosene. He could have used gasoline but he preferred kerosene for its power,after all these dual fuels were designed to run on kero. The poor man's fuel was somewhat cheaper than gasoline but was often preferred because of the tractor's design and ability to produce power from it. For twenty years we used straight gasoline in the M and it worked fine with its distillate head.

I will look closer at my manifold tonight and see if I can find these shutters. I know there was no heat shield to speak of and I suppose that would be an easy thing to discard.

Understood on running straight gas in a distillate. However there is certainly a power loss from the lack of compression. How much improvement will stepped head pistons make? Does anyone have compression or horsepower numbers from an engine with stepped head pistons and distillate head?

if you are building a competetive puller, then go with the high compression head and pistons. i have a 42 m distillate. when i rebuilt it, i used the distillate head and flat top pistons. it does have a gas manifold. tractor runs fine. has good power, pulls the rotary mower, 14tbaler and disk just fine. i also have a 48 m, 52 m and a super m. all will do about the same amount of work in a day, the super will do it a little faster with the higher gears.

ok these are real numbers, not memories. M+W chart shows original m with gas head 36.7 hp and 5.6 to 1 compression. with their turbo-dome pistons 53.8 hp. 6.4 compression. on an m with a low compression head 33.2 hp 4.7 compression with turbo-domes 48.7 hp 6.0 compression. M+W made a set of one inch tall domed pistons for l-p use with a gas head or gasoline use with a low compression head like yours, but they are no longer available. but I have a set just for a conversation piece. so the chart shows a ten percent loss of power with the low compression head.

Do you think the power numbers would be similar using a stepped head piston similar to what they offer here on yesterdaytractor for sale? Also was the M&W pistons 4" or 3 7/8"? Thanks for the numbers that's the kind of info I was looking for.

Not looking to do any pulling but as long as it's apart I figure I may as well get the most bang for the buck. I do plan on using it for a work tractor but it won't be an everyday all day kind of work. More like weekend warrior. Stepped head piston kits for sale on this website are cheaper than the flat tops. Any particular reason why I should not go stepped head pistons with distillate head?

You wouldn't be able to send me a picture of these turbo domed M&W pistons would you? I am curious what they look like. [email protected] Thanks in advance and no problem if you can't.

stepped head will work fine. when i did the 42 m, napa had the sleeve and piston kits for about 90 dollars a cylinder. so thats the ones i went with. if the stepped head are cheaper, i'd go ahead and get them.

I have a '49 M and my block was cracked so I replaced it with a distillate block and head, rebuilt it with new bearing, sleeves, gas step pistons, and rebuilt the head (new valves, seats, springs). I put a gas manifold on it as well. She runs great, no problem with hp, I wouldn't pull it at the fair but it's good for working around the property. Best of luck, ~Anthony

(quoted from post at 13:25:41 04/08/14) I have a '49 M and my block was cracked so I replaced it with a distillate block and head, rebuilt it with new bearing, sleeves, gas step pistons, and rebuilt the head (new valves, seats, springs). I put a gas manifold on it as well. She runs great, no problem with hp, I wouldn't pull it at the fair but it's good for working around the property. Best of luck, ~Anthony

Click to expand...

Great info. Did you have to do anything with the carb to run on gas? I'm guessing mine was already changed over if so but I'm going through everything close so now would be the time to change if need be.

I used the carb and governor off my gas block and didn't need to make any adjustments. I would imagine that the carb off the distillate would work fine, distillate engines started on gas and switched to distillate so they were made to run on gas. Actually, the M I stole the block from had been run on gas for probably 30 years before I took it (transmission was broke bad), when I broke the motor down it still had the original distillate flat head pistons, carb, governor, head, and manifold. I think you'd be just fine with that original equipment. ~Anthony

If you want and your kerosene manifold is in good condition I"d be willing to buy it and or get you a gas manifold email is [email protected]

Don't worry about using the distillate head since you already have it and it's good. Use the step head pistons as others are suggesting and you will have a fine work tractor.

I'm going to bet that the distillate manifold and shutters are already gone and you have a gasoline manifold. Under the "parts and pieces" tab on the left type in "distillate manifold" in the search block and it will bring up one on an H. The distillate manifold is fat all the way down to where the carb bolts on and has a separate bolt on top where the muffler goes. They have an adjustable internal baffle to force the exhaust down over the intake part and get it really hot. The baffle is almost always stuck and badly deteriorated.

The distilate or kerosene manifold looks like the picture below, with a heat adjuster in it (nearly always jammed). Nearly every Farmall H and M in Australia had the kerosene manifold and shutters. Both my Farmall M tractors are petrol / kero. Finding a good kero manifold is difficult…
SadFarmall

Most M gasoline tractors came with a manifold that looked like this. IH replacements and aftermarket ones will look a little different.
If you have the original 39 head it may have 3/8 diameter size bolt holes or studs for manifold mounting verses 7/16 for most.

(quoted from post at 20:23:47 04/08/14) Don't worry about using the distillate head since you already have it and it's good. Use the step head pistons as others are suggesting and you will have a fine work tractor.

I'm going to bet that the distillate manifold and shutters are already gone and you have a gasoline manifold. Under the "parts and pieces" tab on the left type in "distillate manifold" in the search block and it will bring up one on an H. The distillate manifold is fat all the way down to where the carb bolts on and has a separate bolt on top where the muffler goes. They have an adjustable internal baffle to force the exhaust down over the intake part and get it really hot. The baffle is almost always stuck and badly deteriorated.

Click to expand...

Great info thanks. Sounds more and more like the stepped head pistons are the way to go. I checked the pistons that came out last night and they were IH pistons with a 3/8" step. I have to imagine the M&W 1" stepped turbo dome pistons must have been monsters.

I had never used the parts and pieces link on this website. Very useful. Based on what I saw and your description I believe I have some variant of a gas manifold.

Yes, you have a regular gasoline manifold and it will keep on working great.

Of the tractors I have, about 10 of them were originally distillate and only one still had the hot manifold on it, and it was in bad shape. None of them have the shutters, shields or operating rods. One still has the gasoline starting tank.

your manifold is a 400 gasoline manifold. much better than a 'm' gas manifold.

all of the improved power pistons for an m were four inch bore. a lot of people would have the block bored to take 4 1/8" pistons and sleeves.