While installing my shiny new motor mounts I had to bend the dipstick tube a little to get a wrench in place. While bending it back something went "pop" and the tube now rotates freely. What broke? I't's always leaked a little, and there is a generous amount of RTV around it, so I'm not sure there isn't a PO kludge on the inside of the pan.

Sounds like the end of the tube broke off where it enters the pan. Or maybe the PO had it glued in with epoxy/JBweld and copious amounts of silicone to seal it. I guess 1st you could clean all the silicone off, pull the tube out and take a look at the end where it fits into the pan. Worst case will require pulling the pan to check that no crud fell into the bottom. Mine leaks a little too and someday I'll pull the pan again and fix it for good.
Mark.

OK, I dropped the oil pan. Below are photos. I had no idea that the dipstick is slip fit. Looks like the PO tried to glue it in with some kind of white stuff and it was the glue bond that broke. I've cleaned it up, and am guessing that I just need to seal the tube with some RTV when I reinstall it. Also, while the pan is out, I'd like to take care of the leak around the plates that hold the dipstick tube. Any bright ideas on the best way to do this?

Drill the rivets, make new gasket, use machine screws and nuts to bond the two plates over new gasket?

Also, maybe you can find a section of vacuum hose or fuel line, petroleum resistant, that could fit the ID of the dipstick mount and the OD of the tube to help seal things up. Sort of a dipstick bushing of sorts.

That's not a bad idea, and I think I've got some spare fuel line laying around. I was thinking of drilling the rivets, tack welding machine screws to the inner plate and using RTV instead of cork. Or just TIG-ing the whole thing, but I'm a little concerned about the heat input warping the mating surface of the pan.

If you're planning to strip and powder coat the pan and then put it on a clean engine, then I think the TIG makes sense from an aesthetic standpoint. Otherwise, you're just showing off. No offense.

I'd say that 5.8 build you have planned could benefit from that TIG machine, if you don't plan to use the roller block dipstick provision in the lower skirt.

The way I have most often heard of in the past was to braze the dipstick tube in.
Get some heat stop paste to keep the heat away from the mounting flange.

Don't forget lock-tite!

My 76 is leaking profusely from the same place. Was thinking of having it tig welded. You think a gasket and rivets will keep the oil soak out?

I keep going back and forth on the better solution. It'll be a PITA to weld, as the metal will be pretty oil-soaked. I'll likely gasket it and then TIG it if it leaks before I drop in a bigger engine. The cork that's in there now has been in place for 40+ years, so it's not really an indicator of reliability.

my vote is TIG it in. You have the ability to do it. I wouldnt sweat the amount of heat that is going to be produced. If your really worried about it, do each of the corners, let it cool then go back & finish welding after that cools. Now if you didnt have a TIG and had to take it somewhere, I wouldn't do it. Just my $.02

To keep it from warping you could bolt it to a bare block or make a jig to bolt it to.