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MG MGB Technical - Carb Overflow Pipes - HS4

A temporarily stuck needle valve means I now realise that I have no overflow pipes on the float chambers on my HS4 carbs so I am about to fit some. Easier to spot stuff wrong than just missing!

The metal pipes are NCA, rubber fuel pipe was suggested and easy though that would be to fit I think given where they run, metal is a much better bet. I have some suitable 6mm copper pipe, having realised it is the same size as that used by air conditioning firms and courtesy of a very understanding local firm.

Not having access to an example to look I have had a look at several photos online, mainly Hammer and Spanner. Am I right in thinking the front pipe goes between the air filters and heat shield then drops down to the bracket on the side of the block (AHH 7382)? It is not clipped anywhere apart from the clamp?

Any reason not to use fuel hose to turn the 90 deg from the overflow pipe before I connect the copper pipe? The original method looks to be a short straight length of hose with the metal pipe bent at 90 deg, but bending rubber hose is a lot easier!


Mike Dixon

Mike,
if you've got an understanding local firm they might put the 90 degree bends in for you. Just allow a bit extra length of copper pipe for the horizontal (to carbs) as it's easy to cut the copper to the required length after trial fit(s).

They might even lend you an external 6mm spring and/or bending tools for the 90 degree bends and other shallow bends and shaping so you get a nice looking job and good alignment to the clamp bracket.

Best to test routing and what can be put or fitted through where with thick pieces of wire and to also get the form right before shaping the copper.
Nigel Atkins

It doesn't really matter which way they route although they do need to be clipped to something that moves with the engine, my roadster came with them clipped to the chassis side of the engine mount which was tearing the very short rubber hose between pipe and port.

Because the port faces the back of the air cleaner base any pipe has to take a sharp 90 degree bend to turn downwards as you say. I can't see any reason not to use rubber to do that, but there isn't much room, and decent hose is pretty fat. If it fits, it'll be fine.

Once they leave the carbs they are only clipped at that one position i.e. block bracket or engine mount bracket. I've not got a block bracket but it's behind the engine mount so may be tricky to fit, whereas the restraint bracket is quite easy to get to. I fitted that at the same time as I rearranged my overflow pipes, and it was quite easy.
paulh4

I posted some pictures of the routing of mine on here a long time ago. I cant find them now but they may still be archived.
Stan Best

This thread was discussed between 23/04/2021 and 08/05/2021

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