I have a 1955 Ford 850 my grandad bought new from Goshen Implement in Elkhart County Indiana. I have had it in Idaho since the late '70's using for snow plowing some bush hogging and light excavation as I added a Freeman loader about 1980. Been running fine but started sputtering running rough after warming up. Went through the carburetor with new gaskets and such. New fuel tank as the old one started to rust. If you spray ether around the intake side of the engine seems to smooth out for a bit. Pulled the manifold and put on a new gasket set. Same problem. All of the above was done thinking it has intake air leak somewhere. I've been around this tractor for over 70 years but it has me stumped. Next thought was to pull the manifold and take it to a machine shop to see if it is warped. I need some help from those with more gray hair than me.