MD vs. Super MD Fuel Injectors

I have some questions about the injectors,pre-combustion chambers and even the cylinder head on a MD vs. a Super MD. I see on parts lists that the early MD and later MD had different injectors, after S/N 14,500. Are Super MD pump and injectors different? Either physically, or in the amount of fuel delivered. Are the cylinder heads different? I will try to attach pictures of what we have. The lines have different fittings at the injector end on these also.

The injector on the right in the photo came out of a 1947 or 48 MD. The other one is from a Super MTA diesel that had a cracked block. The nozzle bodies are different,and the pre-chamber will not fit from one to the other. I hope this makes sense, thanks.
Garry

Dang photos uploaded twice!

What kind of injector pump on these tractors. One looks like it fits the A pump, the other looks like it is from a osch pump.

The picture with the line still on the tractor is an IHC pump (on the 'regular' MD). I will check and get a picture of the pump that went with the line I was holding up with sky in background. Also will check 2 other Super MD around here to see what kind of pump/injectors they have. This came about be cause the 47/48 'regular' MD developed a skip, and we were wanting to substitute an injector.

Thanks,
Garry

The injector on the right appears to be a american bosch
injector... would have to look at my mds have one with
bosch one with ih system. these should technically only be
used with the bosch type a or type k pump that was used
on early mds, I found that the fittings and lines are
different threads and size. Most mds by the end of the war
were using international type a pumps. The 43 parts book I
have only lists the bosch injection system,I have seen a 46
parts book that lists both systems. Either way those injectors
are desirable to guys with the early bosch pumps.

Take a lot of information to try to explain as it gets confusing and also change over parts used later on.
Between Bosch and IH pumps at least 6 types of fuel lines were used. Some different injector parts and pre cups. Both IH and Bosch pumps used a injector with the hex.
Original MD and SMD used different size injector plates with the same type injectors. On some injector bodies the size of the plate hole is stamped on top below the fuel inlet fitting, like .036, .042, ETC.
Never had the original internals of a MD engine above 14000 and 14000 down to compare.
Often wondered what was different and tried to find a sure answer. Don't know the sure answer but think the compression was raised a little on 14501 and up.
Parts changed out over the years means anything may be found.

I checked the pump in storage building(from a Super MTA) as well as two other running Super MDs. The pumps all have a big 'A' cast into the pump housing 'side plate'. They all have injectors and lines like the injector on the left and the line I am holding up to the sky. Were these 'A' pumps later production, I am guessing. Did they start with the SMD? The regular MD also has an IH pump. It does not have a pressure gauge though. Looking at an old parts book from IH, it appears they used Bosch pumps on about the first 1200 tractors in 1939. They look a lot different from the IH single plunger pumps. Were these IH pumps made under a Bosch license? It seems the injectors were changed at S/N 14,500. Were they changed again with the 'A' pumps?

Were MDs built in the same serial number sequence along with the gas M? That is, did they build 14,500 M tractors of all kinds and then change injector designs? Or was it after 14,500 MD tractors.

Also, at what pressure should these injectors break at? I have a test pump(hand pump) and a box of OTC adapters, but so far have not found a fitting that will fit the injector.

Thanks to all for taking time to reply
Garry

IH injectors open at 700 lbs. Bosch injectors open at 1400, according to my IH manual.

Serial numbers are the engine serial numbers on the engine parts. The IH pumps before the B type for those engines were mostly the same with or without the letter A. Different type fittings were sold for IH pumps and injectors around 3 times on MD tractors. If MD engine serial numbers made it past 22,000 it couldn't be much. Look for part number on IH pump plate to know what pump you have.
Pump use is not black and white. Original Bosch pump A was used to serial 1204 then 4 more Bosch types were used through MD production if specified. Later on IH had a field change package to replace Bosch A type with a type R.
Most of the IH 6 digit R ending pumps have a A on them until the B pumps started during Farmall 400 production for that series of tractors. B pumps are ID by a drip line on the bottom and just 2 lines to primary pump housing. Near end of F 400 production they also started using open type injectors.
Later IH made parts to add later injection pumps and injectors to previous engines if wanted.
Used closed type injectors set at 700 to 710 PSI. If new spring is installed set around 740 PSI.

Thanks guys, we are slowly getting these systems sorted out. My dad has had this MD since 1977 and never really had to do much of anything to it. There is no serial number plate on the tractor. It recently developed a skip that will not go away, even after warming up and running for a while. My dad has worked on diesels for 60 years, truck engines, mostly Cummins with the PT fuel system and some 71 series Detroit Diesels. We also have two SMDs and a MTA diesel, none of which have ever had any trouble with the fuel system.

Also it has occured to us that the skip may not be from an injector. All of the valves have clearance and the starting valves have clearance also. Hard to tell if compression may be leaking past a starting valve. Would that make a distinctive noise?

Also, where do you find the engine serial number?

Engine serial number is just below the head at left front of block and above the injection pump.
Injection pump should have a plate on it with pump part number and a serial number.