Well, the good news is that I sucessfully built a tool out of a 1 inch grade 5 bolt and nuts to remove the precombustion chamber (see attached pics).

The bad news is that one of the two chambers left behind some bad threads when the chamber was removed. The pocketbook drain never seems to end...

At this point I am not sure if I will try to find another head (this one was already pretty lousy), or repair the thread. I found a used head for $350, and since large diameter drills/taps are so expensive, I am leaning towards buying the used head instead of repairing this one.

Can't you have an industrial/oilfield machine shop take a look at it?

I don't know if we have any of those around. I had to call a lot of machine shops just to find someone who would press/machine the new rod end bushings in my D7 connecting rods!

I believe there is a thread repair kit available from CAT, not sure about the cost per hole, but I would go with the used head if it is guaranteed. Pretty hard to beat a "bird in the hand" so to speak.

You could keep the other one and repair the threads if you find that to be cheaper sometime later or sell it to someone and let them repair it.

Bear in mind that good 3T heads are getting real hard to find. If you have located a GOOD used head and itg passes all tests, it might be a good plan to grab it and just hang onto your old one for just in case...

a1 1/8x12 kit is avaible at toolsource for $215 it has 5 coils in it and all the to
tools required jw45 www.toolsource.com/inch-fine-thread-repa...2-1688-p-102825.html

JD45 - Thanks for the source for large helicoils. I actually need a 1-1/4 x 12 kit which is $239. Since the pitting is so bad on this head, I am going to buy another head that I found for $350 that also has good valves.

I have now spent more in new/used parts to get this engine running than I gave for the entire D7. At least I can take pride in knowing that once this dozer is running, it will not be going to China as scrap which was were it was heading before I bought it.

Check with Holf Machine & Welding in Salina,KS and see if they can do something like what you need on this old head. catskinner

Thanks Catskinner. I bought the used head and found it had a cracked valve seat after I touched up all the valves/seats. I am having one heck of a time trying to get the old valve seat out without destroying the head. I have new valve seats if I can get the bad one out.

I will give Holf a call and see if they can help me. It is a long way to Salina, but might be worth it. I wish I could find a machine shop in the Kansas City area that could do this kind of work.

KansasD7

won't the old "weld a bead around it, let it cool and take it out with the fingers" trick work on a valve seat?