MM GTC LP ???

Pete Brandel

New User
I recently bought a MM GTC LP serial # 04701094.According to my records the GTC's ended with serial #04701101.It has 10A150a blocks(403)and 10a4209 heads.The engine model#is 340A4 serial 04000987.The model #is stamped 403 over the 340A4.It has a gas hood instead of an LP hood and has a panel mounted in front of the lp tank to fill the gap.I am adding a picture of that panel.Does anyone have a serial number close to mine that also has this panel?
a183213.jpg
 
The serial number tag on motor reads model 340A4 serial #04000987 but has been restamped over the 340A4 with a 403.Could it be that being a late serial number from the end of the GTC run that they put a 403 in it from the factory? I will add picture of serial number.
a183300.jpg
 
It also does not have valve cover breathers.It has a hose attached to both valve covers and is attached to the air cleaner kind of like a PCV system on a car.Any blow by gases from the valve covers would be burned in the engine from the air cleaner.Has anyone seen this before? I will add a picture of the system on my tractor.
a183301.jpg
 
I believe gtc had a smaller engine than a 403. I
bet what you have is it. The breather looks
modified on but im not sure, ih m's of the same
period used a similar setup of breathing blowby into
the filter like that. I have a 48 gtb and a 47 utu
and they don't have a breather set up like that and
they both use a push pull switch with a starter
button rather than the all in one ignition
switch/light switch like yours, but maybe yours is
newer. Interesting tractor!
 
Got a good mystery going there. I don't know anything but it looks like the tank is mounted backwards and the panel is the what used to be the covers over the valves, etc. The PCV program is likely a farmer modification. I think that the power units had a PCV system but that was done with steel tubing, not garden hose. Just a note, I bought a 97 Massey that had a similar PCV system with the garden hose, except the hose was just routed to a spot behind the rear axle. I thought that was kinda cool until the first time I worked the tractor and discovered why such a modification was made. The blow-by was incredible. An engine overhaul was then undertaken. In any event, "if tractors could only speak", and it could tell us what it's been through!
 
Does that adaptor look like a factory job or did someone just do a nice job of making an adaptor? I had a GTC once but I can't recall, I almost thought that the valves on that tank were on the back like a U had them instead of the side like a GB. Maybe it needed an overhaul and someone put the 403 blocks and pistons in it, then stamped the plate as a 403?? Maybe they needed an new hood for some accident reason and could only find a gas hood so built an adaptor?? They must have been pretty handy and clever by replacing the dash with one off a U or Z. Only thing that I notice is that adaptor sure looks rounded like the original rounded hood from a factory LP tractor is compared to the more flat or oval hood on the gas models. As far as those breathers, it looks like that was bronzed into the air cleaner so that wouldn't be factory I'd say. Interesting, but you may never really know what went on. According to the serial # book, they didn't even make any GTCs in 54. They ended them in 53 and didn't start making the GB LPs until 55 so why would they be doing an experiment at that point in time. Great conversation piece though.
 
Here is a picture of a GTC setup the way it is supposed to look. The LP tank comes forward nearly to the hydraulic tank where on the gas models the gas tank goes over the top of the hydraulic tank thus requiring a shorter hood. Also I noted that on this picture the G tractor is a 1953 model it says and it has that beefier looking bell housing like the ones that were on the later GBs with the rubber plugs still in the threads, our 52 GTB doesn't have that style.
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Does the rearend have the bevel gear rub blocks on the right hand side. That was one of the changes made when MM started putting the 403 LP on the G rearend. MM degraded the 403 to the 340 for LP tractors to protect the rearend.

Or so the story goes.
 
I was going through the forum and found another G that has the same panel between the gas tank and hood.It is on page 23 of the forum under modern view.The author is 71ford100.
 
I have a 403 power unit that has cast iron valve covers and instead of breather caps it has brass fittings traded in the top
And has copper lines run between them and then to the intake port so it creates vacuum and blowby would go back into intake.
 
The information I got from a long-time M-M dealer; The GTC was an LP only tractor (no gas). It had a 340 ci engine with very high compression. the theory: smaller ci engine with higher compression; same HP rating as 403 engine with lower compression using less and cheaper fuel. Must not have worked to well since they did not build a lot of them. The ones I have seen are exactly like the 403 engine tractors in appearance. Just like the original pictured below. This one has been "customized"
 

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