Hi i need to figure out how the fuel return lines are routed on the 20 , i have a return comes out of the block into a t but cant figure out where it goes from there anyone know thanks mike

Have never been around a 20 with the GM6-110. Have 21s which also have the fuel oil torque converter. My return line goes into the torque converter, out of converter into a restrictor value(Which builds up pressure for the converter) then into tank. I have a T fitting in the line before it gets to converter, one side of the T to converter and the other side to a fuel pressure guage on the dash. Good pressure for mine is 30 to 40 lbs when at 60% or more power . Hope this helps and let us know what happens. Bob Ohio

Well think we figured it out thanks to bob and a parts book But now i got a new delima 20s had detroits and 21s had allis/buda motors RIGHT well i got a dozer sittin here says allis chalmers 20 on the side but the serial says hd21a 11583 anybody got any ideas . thanks mike

PS it is DEFINATLY a detroit

Mike, when AC started to make the HD21s, Gm shut off the engine supply. Allis went and bought Buda and started to make their own engines. The engines in the 21 line were all AC. The first 10,000 run had a supercharger on them(like the GM has) From 11,000 they all have turbo chargers on them. I have seen a 21 which was refitted with a GM6-110 out of a 20 into the 21 frame. I have never seen a 20 that had the AC 21000 series engine in it. I have 3 21s here on the farm, one about 11,000 and the other two are 21a's around 18,000. My early one is a short track and the other are long track wet clutch later models. I have only seen a 20 once. I think it had a garwood blade on it. If the serial on the right side of the dash says 21, it probably is. The 6-110 is a power house engine and loud. If you send me an e-mail, i will send you some pictures and you can see what the early 21 looks like. I attached it on my name Bob