I've noted that sometime folks post an issue here, but often forget to post their solution. Even though I haven't seen this problem on the forum, I thought I'd post my solution in case anybody ever runs into the same issue.
Ultimately, the problem is solved. The solution is below.
As some suggested above, I ended up running a tap though the drain back port. Sounds easy enough...and actually it was but there was some gnashing of teeth and nervousness along the way.
First, after countless hours of working on the plane, reading, this forum, I discovered that I didn't know that an AN823-6D fitting does NOT have 3/8 x 18 NPT threads. I assumed (silly me) that the "6" in 6D meant that this is a 3/8 fitting. After a buying the wrong tap and then doing little research I found that the NPT threads on this fitting are 1/4" x 18.
I obtained a 1/4 x 18 NPT tap (not an easy local find)
The thread that was bad was at the very beginning of the port (see picture in post #1). I thought that perhaps a turn or two would straighten/cut a new thread and I'd be done. Wrong. Quite the opposite was true.
Since these are tapered threads, I ended up:
- Pulling the valve cover (found that there is a gob of room for the tap to to run through if necessary.
- Running the tap gently and slowly into the port. I'd remove the tap, flush the hole and the tap every 1/2-1 1/2 turns depending on "feel"
- After each flush, I'd try to reinsert the fitting.
- In looking down into the hole from the top (valve cover off), I noted that even at 3/4 of the way though, I still couldn't get the fitting to thread.
- At that point I realized (hoped) that I just needed to go to the end of the existing threads for the tap to come into contact with the problem threads due to the taper.
- Fortunately, I was right, as the tap reached the end of the existing threads, it came into contact the first couple of threads.
- I removed the tap, flushed, the hole, and was able to get the fitting to thread nicely. With a little sealant, I was good to go. Problem solved.
A couple of notes-
When I went to reinstall the line that goes back to the case, it didn't fit properly and had to be massaged a bit. Why? It's now obvious that these lines are fabricated after the fitting is inserted into the cylinder before the drain back line is made. Just the additional two turns shortened the fitting enough that the flare nut didn't want to thread onto the fitting due to the new alignment with the now "shorter" drain back fitting.
The fitting needs to be perfectly clocked as not only does that flare nut/drain back line have to fit properly, in my case, I have a fitting for manifold pressure that comes off of the #3 cylinder that has to "fit" between t he cylinder and the drain back fitting. If not clocked perfectly, these two fitting will touch. When clocked properly, there is roughly 3/32" clearance.
Yes, I wish I had taken photos, but I didn't.
Thanks for the good input here, it's appreciated.
