I have been rebuilding my 3.8L '64 Mark X’s triple carbs. Everything went very well except with the front carb. That bowl has a 5/16 hole in the bottom for a banjo bolt that allows fuel to flow through the dogleg to the attached starter carb.
The banjo bolt is steel and the carb bowl is primarily aluminum. They seize together and become impossible to separate. Well I broke the head of the banjo bolt off despite my most careful efforts. So how to get the rest of it out? I used alum with medium success. Turns out that you can dissolve it (it’s a pickling powder) in water and then simmer it and place the part in. The steel dissolves but the aluminum is left alone!
This worked quite well actually and got almost all of the steel bolt remnants out! The aluminum threads were too rough to use after it was cleaned out though so time to re-tap it. The original bolt was a BSF 5/16 22 I think. Well I didn’t have a BSF tap and besides thought I should go a tiny bit bigger. So I tapped it with an 8mm 1.25 tap. It worked really…until the raised bit inside the bowl cleaved in two right at the last turn or two of the tap…argh! So what now?
Well AUC2088 is really expensive. I’m seeing $200+ and more like $300 for it. That’s insane for an aluminum bit. So next step before I throw in the towel will be to try a little repair. Use an SS 8mm 1.25 flange nut to replace the lost threads on the inside. I’m going to epoxy/cold weld it in place and then use a 8mm 1.25 bolt (fabbed into a banjo with simple drilling) to replace the banjo bolt. This should work out ok since the 8mm threads I made remain nice in clean through the bottom of the bowl. It’s just that material inside of it that broke off.
This process had been outlined on here before once but thought I’d mention this project. For a non-show car it might be a way to get a carb issue sorted out without spending hundreds! Will report how it works out.