Hello, I am new to this forum. I was wondering if anyone would know what engine is in a D4 Cat that my father in law has. I believe it is a 1950-1952. I inherited it from my Grandpa when he passed on and have no place to store it or run it so I gave it to my Father in law, he has space, land and the money to restore it.  Serial number on the engine is 5T1683 (thinking it is a D315 but not sure).  I was hoping to rebuild the engine with sleeves, pistons etc. for him but have no idea where to find parts. It has a 2 cylinder starting motor on it that I plan on rebuilding also. Any information on where to buy parts would be very helpful. He turned 87 this summer and would like to get this running for him if it is still possible. Thanks Paul 

I am not sure but the 5t should be a 4400 motor

5t is a 1945 and has d4400 engine. I have 5t1600

Welcome to the club, The ACMOC library has all of the books you need for your D4 5T. The Service Manual, Parts Book and the Operation and Maintenance Instructions(OMI). There is even a 32 page sales brochure! You have to be a paying member not just a user to access the library. Becoming a paying member also gives you access to our quarterly magazine. It is a very good idea to read the OMI, it contains information on the clutch adjustment & much, much more.
If you want a paper copy of the OMI I found this one on eBay:
 www.ebay.com/itm/387186686432
Craig

often you can get buy with just a set of rings and bearings in a older machine that is just a restoration to running condition. if your not working it you dont need to go the whole hog.