I just thought I would pass this info on here on moparts.

Have been trying to find a consistent and accurate way to remove broken off idle mix screws in T.Q. carbs. So with plenty of practice and finally finding a really good method, I finally have it!

This will take several pics and descriptions to illustrate the details of broken idle mix screw(s)extraction, so read along:

the first pic is a screw that was broken off almost flush with the base casting on a 6545 truck 440 base, so I really wanted to save an otherwise good base.

I had to first use a cutoff wheel and grind the exposed past the casting broken i. m. screw;
this exposes the od of the screw VS the base casting so the end mill tip can be visually centered over the screw and evens the end also.
**Note that someone already hacked up the end of the screw and used a cutting disc through the dia
of the screw end.**

pic:

The next pic shows the base in my angle vise and on the rt corner of the base is a brace I made to further steady the base in the vise. I set the angle of the vise so the i. m. screw hole was vertical. Also used a small bubble level to level the base in the vise and then tightened everything.

Then the next step was to 'center' the end mill over the broken screw and drill with cutting oil.
The depth of the end mill cutting tip is approx .200".

Then I remove the end mill and replace with a #22 drill bit, set the travel stop on the mill and drill to the beginning of the tip on the i. m. screw.

pic:

Next thing is to replace the drill bit with a 10-32 tap and start re-threading with about 5 turns.

Then remove the tap and base and clean out the debris from the i. m. hole.

I set the base up in the angle vise again and finish taping the i. m. hole, clean the hole again and test-fit an i. m. screw. The screw is lightly bottomed to see if the alignment of the tip is centered well in the hole at the front of the primary bore and it all aligns well!

Pic:

I do get on occasion a broken off i. m. screw or one that is too frozen to unscrew. So I was glad to
finally have a way to save an otherwise good use-able carb or be able to save a rare # hp T.Q. or an #'s matching carb for customers.

If anyone has a broken i.m. screw, let me know and I will be glad to fix it for you.

pic of i. m. screw in place after repair:

I'll have to review this again.

I have a Carter BBD super six base that has a snapped off idle mixture screw. Bad thing is I have many different screws that none match that one