I have found a 1957 12 Cat grader with a 9K Cat rebuilt engine with 2900 hours, will this 9K fit up to replace a 1955 9U with the front pto for hydraulic's, and if not wet clutch I can replace with my existing 9u wet clutch
I am just asking the senior members with the experience and knowledge, I already made one mistake purchasing a 3V, , not all D318 are the same as the 9U as I have learned
The machine is about 4 hours away from me, just asking before making the trip.
Thank You, Ricky

9Kxxxx graders (1938-1945) have a D4600 engine, not a D318. Certainly not a 1957 model.
Are you wanting to put the D4600 in a 1955 or 1956 model 9U?
Grader engines have a different oil pan and non-scavenge type oil pump system, different flywheel and clutch. I have heard of D4600 and D318 engines being swapped in tractors but I'm not sure about swaps with graders.

Correction: It's the industrial engines that have the non-scavenge type oil system but I'd still be leery of a grader swap.

Edit: Well my original hunch was right. Checked the 9K parts book and they used a single section oil pump.

Old Magnet certainly knows the details better than me but I think there may be problems with that swap. I have had a guy that was interested in one of my 9u engines for a grader repower and he decided it was not feasible or at least enough unknown that he did not want to risk it. Mike

What ever you do you need to use oil pickup out of the 9u engine if you want to operate on much of a slope. Young guy found that out the hard way here. He bought a 9u out of the San Joaquin valley that had a industrial 318 engine transplant. It worked fine in the flat land not so much on his supper steep walnut orchard.

If your in California I have a possible transplant. I was told ran well when parked for noise in transmission. But of course they pulled water pump, and it sat out side for 20+ years by now.

Just for reference, I had an early 8T grader (1949) with a 9U D6 engine in it, on the 8T graders prior to the oil clutch, putting a 9U engine in is not a problem, if you have the parts from the grader D318 that need to be switched, oil pan etc, after the oil clutch was used in 8T16361 and up, it would not work.
On the question of will an engine from a grader work on a 9U D6, as noted by others the information you have given us does not make sense, so we cannot give a proper answer. A 1957 8T would have an oil clutch D318 that would not be transferable to a 9U.

I have a feeling there were different power ratings on some versions of D318 and the 8U 9U setup is one of the lowest. Could be wrong.