In Reply to: Ford Model 9N - Engine Clacking posted by Bill Langenfeld on May 03, 2023 at 12:36:45:
1951 8N At serial number 356950 the engine exhaust valves were to changed to the free rotating type and the valve lifters were changed to the adjustable type.
https://fordtractorcollectors.com/identify-my-tractor/tractor-id-history/