Help with firewall and heater box threaded holes...

[AZK9]

Hi Folks...

I'm still busy trying to get the deuce in shape for my NJ to AZ road trip. I'm way behind
schedule, but... I am slowly making good progress.

I have hit a 'dead end' in trying to figure out the thread size and type of a pair of holes
in the deuce firewall... and those in the heater box. I have tried to clean them all out
without causing any damage to the hole threads. Since they were 'caked' with several
generations of hard paint, I will probably have to re-tap the holes.

I've posted two photos of the hole locations I'm interested in, so it might make it easier to
figure out the answer to my question. The orange arrows pretty much point directly at the
holes I'm dealing with.

Any help would be hugely appreciated! Thanks in advance!

 

[AZK9]

To add a bit more info to my first post:

I thought the holes in the heater box might have been the same size as the others on the box, but after removing
a nearby screw... and... trying to put it in the hole (indicated by the orange arrow) it did not seem to be the same.
I did not force the process as I did not want to strip the threads.

 

[rustystud]

I thought they all where 1/4"-20 . It's been awhile since I did my heater box conversion.

 

[gringeltaube]

The "holes" in the first pic are 1/4"-20, as well.

 

[Scar59]

The "holes" in the first pic are 1/4"-20, as well.

yep, 1/4"-20. Try the screw again, this time w/ a littler oil. The hole threads are full of rust and
will not let the screw thread in by hand. Use a small ratchet, in/out a bit. That will clean them up.

 

[goldneagle]

I have a rethreading kit i bought at Sears a long time ago. The kit has 3 different set of taps and dies (fine and SAE as well as metric) They are only designed to rethread or clean out the existing threads. They also have thread files in the kit. This kit is a lifesaver!

http://www.sears.com/craftsman-40-pc-tap-and-die-set-master/p-00952105000P

 

[AZK9]

Thanks folks!

I'll now be able to proceed without fear of stripping out the original threads.
The rust is a problem, but some of the paint layers seem as hard as steel!

As always... the help is MUCH appreciated!