Hello N Board Forum,

I've a 1941 Ford Model 9N S/N 9N57720 and the engine has a noticeable CLACK when running at all rpms. When the engine is pulling the clack diminishes or goes away altogether, however, when the engine is running with no load, the clack is pretty loud. Oil pressure starts out at 40 on the gauge when cold, however, goes down to around 10-20 when at operating temperature. I'm thinking a valve or two may need to be adjusted, however, have learned the early N engines didn't have easily adjustable valves and this was changed at some point during 9N production.

Does anyone know the serial number of the engine when Ford went from non-adjustable valves to easily adjustable valves and/or the rotating exhaust valves?

If the valves are easily adjustable I can accomplish this by removing the intake and exhaust manifolds and if they are not adjustable I understand I'll need to remove the head and replace all of the existing valve assemblies with adjustable valve assemblies i.e., a much bigger job. Thank You!

Years ago I had a similar very noticeable clack noise on my 1951 8N. I was just positive that I had a bad rod bearing. With some friendly advice from a Ford tractor mechanic, I checked the exhaust manifold by the very rear of number 4 cylinder. With the tractor running, I put my hand about an inch from the manifold. I was getting leaked exhaust pressure from between the engine block and the manifold.
I removed the manifold and found that the gasket had disintegrated and metal was worn/burned away from both the manifold and the block.
Just a suggestion to check this before going too deep into a repair.

Thank you for the reply John,

I've checked for an exhaust manifold leak and didn't find one though I will go ahead and check the seam between the manifold and the head where I can. I'm thinking I'll probably remove the intake/exhaust manifold any way as it will make it easier to adjust the valves and I'll need to remove it in the event I have to replace all of the valve sets to adjustable valves.

Thank You, Bill

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/

Hi Deanostoybox,

Thank you for your reply. I was hoping the engine valve upgrades had taken place much earlier. I'll remove one of the inspection plates on the right side of the engine to see what type of valves are present and proceed from there. Possibly, someone before me upgraded the valves to the adjustable type.

Bill.