Ford 420 injector not seating?

[kz1000]

Hi Guys,
I seem to have a unique problem that I am dealing with. I Just did a compression test on a 420 and the rear cylinder was low, after further exam I found that I was not seating tight. I am using a fuel injector from that tractor as a compression checker. I installed the regular injector with a new copper gasket and the same thing. It looks like the seat may have damage from years of leaking or what ever. Question is how to get a good seat without pulling the head for machine work? Thanks!

 

[Harry in Ky]

I don't know what others do, but I have some end mills I've collected over the years that fit the bores for the few different size injectors I deal with. I ground six flat spots on the drive end that will let me slip a six point socket onto. Put the mill in the hole and trun it slowly with a speed handle. A SLIGHT but steady down pressure and slow turning speed usually cleans up a rough surface. It's easy to do damage, so I cut a few turns and inspect the hole frequently until it look good enough.

 

[kz1000]

Thanks! I was thinking along those lines. Do you put a little grease on the mill head to catch the filings?

 

[Harry in Ky]

No, I never used grease. I roll the engine to get the piston at the top first, then use a rod or screwdriver through the hole and insure the piston is at the top. Then mill a few turns, hit it with air to blow the chips out. Check the surface for effect, and repeat.

 

[kz1000]

I thank you for your time sir, I'll mic that hole and see what fits.

 

[Harry in Ky]

It's not that critical. Just measure the injector bodyand the seal washer. The mill needs to be a only slightly bigger than that but still fit down the hole.

 

[kz1000]

Got'er did, I think most was crude build up. Thanks for the help all. now it's off to find a 641 big spline shaft for between the rearend and transmission of said tractor.