valve clearance changing

[Rich M]

In reference to a earlier post, if the cam needs replaced where do you suggest. Any certian grind?Tractor also has new valve srpings and valve clearance will change by turning tractor over two three times

 

[finn1wil]

could it be you are turning the engine over backwards and adjusting valves in the wrong position? Look at your adjusting screws, they should be reasonably consistent in threads above the jam nut.
good luck

 

[great dain]

Had a problem like this with a John Deere 630, I would set the valve clearance run the motor recheck the valve clearance again and it would not stay consistent. The tractor never ran good. When i sent the cam in to get reground they could not grind it cause it ran out .128 or about an 1/8 of a inch. That's one possibility, another one could be a bad cam bearing. Good luck, Great Dain

 

[Rich M]

will check cam bearings also,thanks

 

[S.Crum]

Another common cause is worn valve guides and/or worn valve stems. An yes the valves will actually hang up due to these even with new springs.

 

[Rich M]

great dain ,pulled top cover but found no play in camshaft. thanks

 

[Dodgeit]

(quoted from post at 22:13:23 02/26/12) great dain ,pulled top cover but found no play in camshaft. thanks

Just for fun I would look to make sure the lifters are free in their respective bores, and that the push rod bores are also not gunked up.

Also that the rocker arm assembly is free and not worn out, and that the rocker arms where they contact the valve stem are rounded slightly with no grooving or flat spot, the same for the valve stem. It should be flat with no abnormalities.