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MG MGA - Bolt size - carb float chamber

What's the socket size I need for those banjo bolts that secure the float chamber to the carb body? (The bolts securing the lid to the top of the float chamber are also the same size). Thanks again...
L.R. deOlazarra

i'm not positive but i think it's 5/8. Maybe 11/16th
Judd Irland

The bolt is 17/32", so a 14mm socket will fit. Some carbs have a stud with a nut, but I don't have this set up so cannot help with the nut size.
P. Tilbury

Thanks for the imput... (Peter; I have the same bolt style you do) I have the U.S. and Metric sockets, and yes, the 14 mm will work, but not quite. (13 mm too small, 14mm too big. Same with 1/2" too small, 9/16" too big) Though they may exist, I haven't run across a 17/32 socket; 'course I've had no reason to look for one yet. The bolts I referred to are one of the few instances of hardware on the MGA that don't easily accept the standard American sizes I have lying around. I ran across a cross-reference chart that put a British size (BS inch) of 5/16 smack dab between 13 and 14mm. Anyone know how I could get a socket of that size? I don't know; maybe I'm being too picky and should just suck it up and keep using my teeny-weeny adjustable wrench or continue chewing up the bolt with oversized sockets... :)
L.R. deOlazarra

I think you will find a 1/4 Whitworth will fit, but can't be sure since I fitted the Judson
dominic clancy

I think all the screw hex. head sizes on the SUs of that period were Whitworth/BSF. Certainly the top of the float chamber screw has the same head as a normal 5/16BSF screw/bolt and the banjo bolt on the incoming fuel line has a normal 1/2"BSF/7/16BSW head. The socket you want is 5/16BSF/1/4"BSW but you could get a cheap set for less than 20. You won't use them much on the MGA but they would come in handy if you ever get a slightly earlier british car! Immediate post war cars were still using BSF/BSW threads.

There's no shortage of the sockets on Ebay UK.........Mike
m.j. moore

One of the smaller spark plug sockets (IIRC 10mm) fits the oil filler on the top of the carb. It is not the same as the socket for the spark plugs in the engine!
Dan Smithers

Just for the record the BSW (British Standard Whitworth)spanner/socket sizes for the various SU carb. hex heads/nuts are:-
Jet adjusting nut - 5/16"
Jet locking nut - 7/16"
Central nut (float chamber lid 'screw') - 1/4"
Float chamber retaining bolt - 5/16"
Banjo bolt (fuel inlet) - 7/16"
Brass damper hex. - 7/16"

If you see BSF spanners/sockets for sale don't forget that these sizes are all 1/16" up, e.g. 1/2" BSF and 7/16" Whitworth spanners/sockets are the same size .................Mike
m.j. moore

Dominic, Dan, thanks you for the input, and Mike; thanks for going the extra mile! I understand what's going on now and what to look for...
L.R. deOlazarra

A small adjustable will fit the oil filler nut on the top of the dash pot, the bolt on the top of the float bowl, the bolts on the fuel pipe banjo inlets, the nuts on the fuel pipes, the jet adjusting nut, and the bolt holding the float chamber. However, I am not suggesting you can get it into all these places!
P. Tilbury

Right! These cars can be such a bear when it comes to engine access; any tool that can help... The Spitfire I had before this spoiled me; just lift the front end out of the way, sit down on one of the tires and have at it.
L.R. deOlazarra

Is that a metric or an imperial adjustable Peter!
Lindsay Sampford

For this application it is actually a Whitworth adjustable. Funny thing is, you just turn it over and it becomes an AF adjustable, and turn it over again and it becomes metric adjustable. Must be magic!
I have another one where I have ground down the jaws so that it fits in tight spaces!
P. Tilbury

You maybe ionterested in my trick for shifters (Oz slang for an adjustable spanner). Cut an extra tooth on the adjustable jaw rack with a file or grinder(you need to remove first)so that it is possible to screw the jaw out completely when assembled. This allows it to fit that nut that was just too big before!
Mike Ellsmore

Hey Mike,
I like that idea of a stretchable adjustable!
P. Tilbury

I think you will find the banjo bolts for the master cylinder, rear brakes and fuel pump are also Whitworth.
R. D. De Fauw

This thread was discussed between 01/02/2011 and 04/02/2011

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