McCormick o-12 valve question

[Geoff]

Hello All

I need to regrind the valve seats on an O-12 head. Can someone tell me the angle they should be please?

Geoff in Australia

[jfkleinrt]

Hi Geoff,

 

Nice little tractor

[wowsk]

On all the engines I've done, including a C-113 for a Farmall A, I use 46 degrees to provide a one degree interference fit between the valve and valve seat. I've never done the valve on my F-12 though so they could be different. You should be able to tell when you get them out.

I use 45 degrees for the valve seats. I used to do a 60 and 30 degree stone to get a bevel to improve air flow. I now only do a 30 degree as most of the time the valve seat are worn on these old engines and I don't think the 60 degree does much besides using up material. These are not high RPM, high performance engines either.

I am no expert either, so if anyone has any corrections to the above let me know, I'm always looking to learn more. I just got a valve and seat grinder a few years ago because I got tired of waiting for machine shops. Everyone is backed up for months anymore.

[hillman]

I got an I&t manual with a bunch of more common manuals if you have any other questions 

[HydroTek]

Our machine is setup with 44 degrees on the valves
and 45 degrees on the seats

30 and 29 for those engines that us that angle 

[Geoff]

Thanks for the replies. I am new at this so would like to get things correct.

Geoff