A few weeks ago there was a thread on a mysterious fuel leak coming from the engine side of a car with dual Weber IDF carbs. I guessed it was the lead plugs failing under the fuel bowl. If one of these plugs fail, your fuel bowl will empty directly on to your hot engine, and you may well burn up your car! I knew my plugs were failing, so today I fixed them.

Chris from Tangerine told me how he likes to fix that problem. After I had done a few steps I thought about taking pics for a how to, so sorry that it seems I don't have pictures of everything.

First off, here are the things you are going to need to do the job:

• 3/8 24 tpi tap
• 4 x 3/8 24tpi set screws
• 21/64th drill bit (or what your tap recommends)
• high temp thread sealant
• Allen wrench for the set screws (not shown)
• drill bit suitable for drilling out the lead plugs (not shown)
• electric drill (not shown)

I should say that Chris DOES NOT use the thread sealant, but Red Loctite. I went with the sealant as I have never had self tapped threads be perfect. YMMV on this one. If you use a sealant, make sure you get one that is not gas or oil solvable.

1) Pull the carbs off the car. The plugs you want to remove are on the engine side of the car, so you are going to need to remove the carbs from the car to do this.

2) Remove the linkage, emulsion tubes, carb tops, etc. You want to be able to look into the fuel bowl. If you look in there and its gross, its also time to rebuild your carbs. Do it, you will be happy that you did!

3) Used a suitable drill bit and a slow speed on your drill and remove the big lead plugs. If they are already failing, they are going to come out easy. Mine certainly did.

4) Use the 21/64th drill bit to drill out boss so that it is the correct size for the tap.

5) Use some light cutting oil to lube the tap, and tap out the bosses. You now will have something that looks like this:



6) CLEAN. Clean clean clean. You will have metal flakes in the fuel bowl, emulsion tube holders, and new cut threads. THEY ALL GOTTA BE GONE! As you can tell in the photo below, I am getting close, but there are still a few chips that need cleaning out.


7) Apply sealant to the threads of your plugs and turn them in. I put mine in pretty tight, but not tight enough to worry about stripping out threads or breaking the boss. If you are using Red Loctite, this will not be an issue for you. I used sealant, so I wanted the plugs to be well snugged in there.


8) at this point, you are done this job. If you have crud in the bowl, get some seal kits and rebuild the carbs. You are already 1/2 way there. If not, put it all back together and put them on your car.

Zach

Dude, you have the same old school webers i have. What sort of vents/jets/tubes are you running? And with what sort of engine particulars?

Its a 2056, Raby carb cam, ceramic lifters, Mallory ignition, etc.

30mm Vents
4.5 aux vents
130 Mains
200 Air
F11 Emulsion
50 Idles

This tune is very close, though I still futz with sometimes. Last summer I tried going up to 55 idles and 135 mains and started getting fouled plugs and missing when cruising under no load.

Zach

Wow, i have a similar build, yet I am running 65 idles, and the plugs, I think, show leanish running visuals when i read them after idling. I am pretty happy with the lack of hesitation when i mash on it, however, i feel like i am missing low end grunt. Also, a couple days ago, i started noticing that its not firing right off. I have about 4k on this motor, and just did a valve adjust about 500 miles ago. Hmmm.

Have I created a How To for a problem that only I have? :-)

Zach

I've seen the plugs fail, or at a minimum weep a little fuel, on so many Webers that we recommend the procedure to every one of our customers who's getting any carb service here.

My carbs are fully disassembled, so I guess I will be doing this now.

The walls of those plug holes look a little thin.
Anyone ever have trouble with breaking them while threading in the plugs?

Also, there are more than just those two.
Are they the "problem children" and the rest never leak, or have other people replaced all of them.

Stu