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Front SU Carb Leak - Advice?

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Shinsen774

Shinsen774

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My front SU has just started to leak from the bottom of the float bowl (I think). The carb on the car has a brass fitting (red arrow) while the carb from my spares box has a nylon fitting. The carb on the car has a line that has a coil around it (green arrow). The spare has a plain rubber line. I don't think it's leaking from the other end (yellow arrow). This just started after I head my head rebuilt. Links to pics below. Your thoughts? Simple tightening of the fitting or more? Keep in mind that I am a novice at this. Thanks.
Jim, '64, stock carbs.
 
How about now?
 

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There is a stepped o-ring behind that brass nut which has probably disintegrated. You can buy a rebuild kit, or find a couple small o-rings to replace it with. You may want to replace both sides. This is a major safety issue!
 
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Best approach is to bench the carbs to do it. There can be remnants of the old O-ring you will miss if you try doing it on the car.
 
Presumably... that seal will be a scaled up version of those I'm familiar with on the HS2 carbs. It would therefore be a square cross-section ring, not exactly an o-ring. The seals are part of the HS2 rebuild kits so presumably (again) they would be in the HS4 kits also.

However, when I had one fail I didn't have any spare parts so I found a good quick fix. The flexible jet tube that goes into the float bowl has a nipple on it about 3/16" in diameter. I bought a short length of 3/16" low-pressure fuel hose from the parts store (it's not a common size... you'll have to ask for it). I razor cup a 1/8" thick disk off the end of the hose, then I carefully sliced through the outer jacket to expose the fiber braid between the layers of rubber. Peel off the outer jacket and the braid and you're left with a square-section disk just the right size. It's an inexpensive, safe, and you'll be back on the road in no time.

BTW, the DR. is right... much easier to fix on the bench than in the car.
 
Expect that I would see if it would tighten just a bit first. But those o rings do get hard over the years.
 
Thanks folks. As always y'all are very helpful. I went through the two foot lockers full of parts that came with the car looking for a mirror to use to see better (which I found) and found a partial carb rebuild kit with a brand new ring in perfect condition. If Jack's solution works, I'm done. If not, at least I have the ring and can start addressing replacing it. Thanks.
 
Get a new gland ( squarish looking o ring made form Viton) and the brass washer from Joe Curto, fixed that leak more times than you can shake a stick with Curto parts. Looking at your carbs though, it kind a hodge-podge of parts there, I think I would just get a new rebuild kit form Curto, which will come with new jets, and tubes, that rubber hose in the second picture is in no way correct. Make sure when you repalce the galnd, you get the old one out first, they are famous for staying in there, a good pick will pluck it out.
 
Hap said:
Make sure when you repalce the galnd, you get the old one out first, they are famous for staying in there, a good pick will pluck it out.
Click to expand...

That's why they need to be on the bench to do the job. Too many times we've seen a leak at that jet supply fitting due to "double seal" problems.
 
The hodge podge is the extra carb in my extra parts bin. It does have a weird set of fittings on it. The carb on the car seems to have a Moss jet assembly (green band). I have it apart and on the bench. Reassembly to occur on Saturday. I had a new o-ring/gland in the parts bin, and the washer is good. Thank you very much for all of the advice and wisdom. I should be running by lunch time Saturday.
 
All glands are not created equal, but it appears slowly Moss and others are wising up and buying Joe Curto's British Standard SU carb parts line, but I still buy directly from Joe, that way I'm darn sure I don't get any China made crap, it's well worth just to get to shoot the BS with Joe on the phone (real good guy), plus he's built more SUs than most of us have ever seen. I had a fellow club member who had been buying glands for his Midget for 10 years from VB, and thay always started leaking about a year down the road, I turned him on to Curto, and now I'm the guy's hero, three years after the Curto glands, no more leaks, bottom line "Joe Knows"

https://www.joecurto.com
 
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It just don't make sense to chance a fuel leak right over the exhaust manifold.
 
Thanks for all of your advice folks. I am back up and running today. Turns out the gland/O-ring was disintegrated, but the fitting has also broken apart. Parts came last night and everything is running beautifully today.
 
Excellent, might be a good idea to think ahead and have a rebuild kit on the shelf one of these days.
 
A footnote to this discussion. I noticed tonight that the jet the B-Hive sells is the one with the black nylon fittings and black rubber hose on my "spare" carbs shown in the photos above. I bought the Moss kit from LBCarCo with the brass fitting and clear hose wrapped in the coil.

Link here:

https://bhive.tierranet.com/images/101-203.jpg
 
jlaird said:
Excellent, might be a good idea to think ahead and have a rebuild kit on the shelf one of these days.
Click to expand...

Have you ever noticed, that when someone gets rid of their MGs, they usually have a ton of spare parts lying around! Gee, I wonder why?
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Whoops! I've gotten "rid of" exactly four MGB's in thirty years... and I ~kept~ all the spares every time!

...mebbe THAT's why I seem to always end up with another one... :smirk:
 
PAUL161 said:
Have you ever noticed, that when someone gets rid of their MGs, they usually have a ton of spare parts lying around! Gee, I wonder why?
Click to expand...
Because if they had installed all those spare parts when needed, the car might not have broken down so many times and they would have kept it.
 
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