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MG MGB Technical - Carb needle valve question

Now that the 67 B Gt has been running for a few days, it has developed a sticky carb needle valve. I have cleaned the valves and the seat area but they are still leaking out the overflow.

Suggestions requested on if I should go with original or with aftermarket ball type?
Bruce Cunha

I'm not sure why people go with the ball type. Needle valves have been used for a million years in carburetors and to my knowledge they haven't been seen as a weak link. If the industry had thought balls were better they'd probably be in more OEM carburetors. Off hand I can't think of a single OEM carb that uses a ball valve.

Just my opinion.

Matt Kulka

I finished up with neoprene tipped needle valves as mine stil overflowed even with a new fuel pump. Of course first stop was cleaning the existing needle valves and second was new needle valves.
S Best

Been there before, no cure, fit new needle valves but not ball valves.
Iain MacKintosh

Could be just flushing out some muck if it has had some major work. Disconnect the fuel pump with the engine running and let the engine empty the flowt bowls and stop, then reconnect the fuel pump. The resultant rush of fuel through the now wide-open float valves should shift any loose stuff. If that seems to do the trick for a while but it then happens again you may need to fit a fuel filter.

If it starts leaking again straight away then you will have to check the floats themselves in case they are punctured and not floating properly, and if not replace the float valve. However that should only affect one carb, if both are affected then either the fuel is very dirty and the system will need flushing out (you could fit a filter but it ould get blocked and start restricting flow quite quickly), or if you don't have the correct SU pump you could have excess pressure overwhelming the valves.
Paul Hunt 2

Carb kit with new needle valves is only $20 (per carb) at my local parts store, so I will do a replacement this weekend.

Amazing, but I live in a small town in rural Wisconsin and we have a major auto parts distribution center in our town that has had a very large selection of MGB parts. I was able to get brakes, hoses, carb parts, and even things like rotors, calipers etc, from them.
Bruce Cunha

We had a discussion about ball vs. needle valves and I think the conclusion was something about the new Grose Jets (ball type) made since the mid 90s being crap but those from years before actually working as claimed.

Regardless, Viton tipped needles have always worked well for me in all sorts of vehicles, when I have been lucky enough to find them. However, you might want to check to see if the float valve's body is sealing where it seats in the float bowl cover. Sometimes they get screwed in with no gasket and will leak. Also, check to see that when it is tightened in place that its force doesn't reveal a crack in the float bowl cover casting at the threads. That could be a source of a leak as well. If so, replace the bowl cover.
Bob Muenchausen

Thanks Bob. After posting, I found a set of grose jets in with my MGTD parts. This would indicate I once bought a set and put them in my TD. Must not have liked them as they are not in there now.

Problem is when the car is not running and I have the key on. I get fuel out of the front overflow. When the car is running, I don't get the overflow. I will inspect the seat area when I install the new carb kit.
Bruce Cunha

This thread was discussed between 22/09/2005 and 24/09/2005

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