I have a '72 MGB with the standard HIF SU carbs. Usually they work
> great, but the front one has recently been leaking. I had someone
> do an overhaul, assuming they'd replace all the seals and find any
> issues, but it is still leaking. Taking a closer look at it myself,
> it is definitely the float bowl seal, leaking around the square "O"
> ring. The ring looks to be in good condition, and the screws were
> tightened down appropriately. I tried a new (round) "O" ring and it
> leaked just as much, if not more. In its current condition, screwing
> it in doesn't completely close the gap around the ring seal, thus the > leak.
>
> It looks to me like the bowl cover is warped. When I invert it on a
> flat surface, the corners touch and the centers of each side are off
> the surface. Is this normal, or did someone tighten it down too hard
> once and bent the corners in where the screws go?
>
> Do I need to get a bigger O ring or a new float cover?
>
> Thanks,
> sln
> --
> ======================================================================
> Mr. Shannon Nelson Parents can't afford to be squeamish.
> sln - at - onemain dot com
In theory that seal should never have to be used as the fuel level is controlled at a lower level by the float and needle valve, so the seal only gets to work in very heavy acceleration or braking. Infact most SU float chambers have a vent pipe or hole in the lid which releaves any pressure build up from fuel evaporating.
Take the lid off, invert it, and blow into the fuel entry pipe - the weight of the float (if the plastic variety) and the fork (if the metal variety) should easily be enough to seal the valve. Probably worth removing the float, and thus releasing the moving bit of the valve, and rotating it by hand a few time to clean it and its seating. Check for leaks in the float (shake it - anything inside?). I presume yours has the plastic, non adjustable needle / float arangement, but if it is the earlier style with the metal fork resting on the float, check its resting point as per the book and bend the fork if not correct.
Good luck,
Andrew Mawson