MD valve recession spec

[farmall pete]

I've been looking all over for a spec on intake & exhaust valve recession for a Farmall MD. The head is at the machine shop and they're installing new valves & seats. They work on a lot of Farmalls, but they can't find any info on the recession spec. for an MD.

Anyone out there have the spec? Thanks!!

 

[D Slater]

All I ever found is 0.125 from head face to valve seat face. Top of angle on the valve seat. Start valves 0.3125.

 

[farmall pete]

Thank you. I'm not following on the "top of of angle on the valve seat" part. Can you clarify?

 

[rustred]

just as it says to the "top of the angle on the valve seat" the seats dont come ground , they are square.i dont think you have anything to worry about , as your replacing the valves and
seats , so things will be as good as factory. problems start when the seats are reground and the valve faces , which makes the valves sit
lower, which will lower the compression. that is when you worry about valve recession.

 

[Janicholson]

This shows the valve and seat. The seat and valve must stay as factory depthe into the port so (as noted) the compression stays as high as possible. Recessed
valves make an MD difficult to start. Jim

 

[farmall pete]

Thank you Jim. I understand valve recession and its importance in diesel engines. I am confused by DSlater's initial comment. First he states the dimension from face of valve to face of head. This is the dimension I was asking for. But then he added "top of angle on the valve seat." A new valve stands proud of the valve seat, with its bottom (facing combustion chamber) face slightly higher than the top of the valve seat. This is what I am confused about and requested clarification on.

 

[farmall pete]

Never mind found the answer to my own question. He is giving the dimension from the valve seat face to the head face, not the valve face to the head face.

 

[pete 23]

Tractor mfgs were really poor about giving valve recession. They gave a lot
of other specs but never dealt with it . Another spec they never gave was
piston height over the block. It was not just IH either as when I worked at
Deere they were even worse on fairly modern engines.

It was not even taught in the vocational schools. I trained in a young man
and he worked with me for five years. Then he went to his true love at Deere
dealer and they fought him tooth and nail when he wanted to hold recession to
some specs.

Then, a former IH mechanic, who went on to be an instructor at a different Vo
Tech ran into the the same thing. They were not teaching it.

I never saw any specs for a MD to 450 diesel about valve recession in any
service manual we had.

The machine shop I used could get most specs as he belonged to a rebuilder
organization that the name escapes me. They seemed to have insight to the
engineering departments that were never printed in our service manual. It was
always a struggle to get past the desk jockies for some real information at
IH and Deere.

 

[Janicholson]

From My recollection, the valve head surface is near flush with the head surface. as in the illustration. Jim

 

[farmall pete]

Maybe the organization was abbreviated AER Pete. I had a conversation with Jim Warehime earlier and he mentioned that is where his machinist found some info.

 

[farmall pete]

Thanks Jim.

 

[farmall pete]

As a follow-up, I talked to my machinist this morning. The spec they use is face of valve to face of head. The old valves measured at .030 - .060

I believe the spec for the later 400 & 450 diesels was .040-.120 The machinist thought this made more sense based on what he had seen with the existing valves, and it makes sense there would be a range to allow for future valve grinds.

The machinist was (rightly) hesitant to recess the valves any further than what was existing, so we are going with the .040 spec.

 

[rustred]

i agree also with them, you want to stay at the top of the spec. and your old valves were not recessed too much either. just that the seats
are getting wide on them, and by the time you get them reground with the valves you will be at bottom of spec. and with the valves at proper
height and seats ground to spec, the valves will also run cooler. sounds like a good shop.

 

[D Slater]

Have two 277098R1 castings off the engine that I think was the last replacement head for some of the diesels.Seen them on late MD
through 450. One looks to have a thinner margin below valve head and valves dropped into seats more. It measures .060 to .075 from
valve head to head surface. Other one has valves setting higher and margins that look to be never cut. It has in the area of .025
to.030 down. Both have IH valves. Can't tell if heads were surfaced in the past.

 

[Steven f/AZ]

Click below...
IH Blue Ribbon M MD

 

[farmall pete]

Awesome! Thank you! I could not find a valve recession spec in there, but so much other valuable information.