M-Farmall Cylinder Heads Valve Length and Geomety

nutty14 · Oct 12, 2011

Hello,

I am wondering if their are different length valves for M-Farmall engines. I recently had a valve job completed on a different head to put on my Farmall. The rocker arms have zero adjustement all the way. I am thinking of shimming up the rocker arm assembly but I would like to know the exact valve heighth difference if any.

Thank you

Scott N.

rustred · Oct 12, 2011

the head on my 400 has longer valves.they are 6.070 in length and part # 362436r1. you may have a 281 head. need to check the pushrods also and see if rockers are the same.

randy hall · Oct 12, 2011

there are three different valve lengths for m heads.

Janicholson · Oct 12, 2011

It will not be happy that way. The repair shop should stand the repair to put in the correct valves. They should also throw in a new gasket!
Spring height specification will determine what is wrong. Shimming the rockers will change the geometry and push sideways on the valves. Not a best practices tactic. Jim

rustred · Oct 12, 2011

dont see how its their fault when they do a valve job on a head that he brought to them he said it was a diff. head. yes diff. heads fit on that tractor. i take it as he brought in the wrong head and they did what he wanted. he would need the pushrods and rockers that match that head.

Owen Aaland · Oct 13, 2011

The installed valve stem height is the same no matter which head is used on the M. If the valves are too long your replacement head is either for distillate or kerosene. Gasoline head valves are the longest.

The machine shop should have know the installed valve spring height was wrong. They would have needed a lot of spring shims to get the height correct, enough to know that there was a problem with the valve length. even if they were such a thing as longer push rods you would need to raise the rocker shaft enough to compensate for the increase valve height and without a lot of spring shims the spring pressure will be way too weak. Then you would need to lengthen the oil supply tube to feed the rocker shaft. When you got that done the rockers would most likely hit the vapor vent tube and may even make contact with the valve cover.

The only real solution is to redo the job and make sure the valves are correct for the head being used.

D Slater · Oct 13, 2011

Adding to the information posted there's a slight possibility you have a head that a tractor puller had .125 or so removed from head gasket surface. Or are you a puller?

Janicholson · Oct 13, 2011

In my opinion and with respect, The rockers and pushrods, and stands are all the same length between heads. The combustion chambers differ between Distillate, Gasoline, and (on later vintage heads that will fit an M) LP heads. This difference changes the length of the valves to get to the seat depth in relation to the engine deck. Thus any head rebuild (done correctly) would have the correct valves for the head installed. This is true even if the head was delivered with the wrong valves. The repair shop uses specifications for spring height, valve length, and other critical measurements to assure their repair won"t come back. If the work was done on a hollow core door behind the oak, on 9 cement blocks, and the valves were ordered based on the words M Farmall, the rebuilder is still at fault. If the tractor owner supplied the valves, and said "put"em in", or rebuilt the head in their own shop, then s/he is to blame. Jim

M-Farmall Cylinder Heads Valve Length and Geomety

nutty14

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rustred

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randy hall

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Janicholson

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rustred

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Owen Aaland

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D Slater

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Janicholson

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