The D318 replaced the D4600. I have a 1945 9K No.12, Motor Grader D4600 and a 1954 8T No.12, Motor Grader D318. I believe I have read on the forum here, at least on the D318, that the crank is just a little bit different in the motor grader than other similar D318, engines. I don't know if the D4600 has the same trait with the crank, though I would at least ask around and keep an eye out. Just thought I'd give you a heads up.
My old 8T (AD UM) runs fairly well, I haven't had a chance to work on the 9K (Kay) yet. 🙄
