joeld

Rebuilding a Q-jet and noticed a small lead plug was loose, approx 5/32 diameter. Tried to re-stake it but it just fell out. I thought about using JB Weld to just fill the hole, but not sure how that stuff will hold up with constantly being in gas. Or tap the hole and use a screw wiht some sealer around the threads?
Any thoughts?

Thanks
Joel

Apeiron

One of the bottom well plugs?

sofakingdom

iTrader: (1)

JB weld works fine, as far as that goes. It is impervious to gasoline. So does tapping and putting in a screw (with JB Weld on the threads). One thing that WILL NOT work however, is silicone.

But that's just the tip of the iceberg.

What you have just come across is the #1 killer of carburetors... galvanic corrosion, caused by the contact of dissimilar metals.

Every place where 2 different metals touch, creates a little battery; and over time, the current produced by that, erodes one of the metals. The more "noble" metal (an archaic term for sure!) survives, and the more "base" metal corrodes into nothing. In the case of a carb, the metal that erodes is almost invariably the chinesium of the casting.

The reason the plug fell out is because the casting around it has turned to white powder and disappeared.

You'll find the same thing happening in the screw threads, the hole where the seat screws in, the air bleeds, and everywhere else that a brass or steel thing is touching the pot metal. If you clean all that white powder off and look at those places with a jeweler's loupe or low-power microscope or similar strong magnification, you'll see how badly pitted and damaged the pot metal is.

In short, your carb may be beyond "rebuilding". You might get lucky and it work out, I hope it does, but don't be too surprised if you get it all put back together and it still acts weird in some way or other; or, screw threads start to strip as you try to tighten them.

joeld

Correct

Joel

Apeiron

JB Weld

joeld

Actually the inside was fairly clean, considering the carb has been in use for over 20 years with long periods of not driving vehicle. There was some "powder" on the walls and around the brass seats. Reason for the re-build is simply the float appears to have finally soaked and raw gas was blowing out of the vent hole.

Joel

sofakingdom

iTrader: (1)

"The inside" isn't the problem; it's where 2 different types of metal are in contact. You'll find the metal in the screw threads and similar places is eaten away, including the threads themselves, if the process has advanced itself far enough.

The reason the plug fell out, is because the casting around it has eroded. Long periods of disuse are the worst for it, because moisture gets in the joints and works its magic.

If you saw the white powder on "the inside" on the large exposed surfaces, you can be sure it's in at least some of the other places as described.

Good luck; but I don't expect your project will be trouble-free as it nears the end.

joeld

Just a update. I did tap the hole and used a 10-32 screw with JB Weld around the threads. Carb is back on, running fine. If I notice any signs of leakage I'll report back.
Thanks again for the replies.

Joel