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MG MGA - Help: SU Butterfly - screw thread?

Hi guys,

I'm thinking of Vizzarding my carbs (not the whole hog, just a little), and as such I'm after some alternative screws for the carb butterfly.

Ideally I would like to keep the same thread, and that seems to be where it all falls down...The part number is AUC1358, and is readily available, but I would like a different head, i.e. Alun-key style like Vizzard mentions.

Does anyone out there in MGAland know what the thread is on this screw?

Many thanks and a belated happy Easter,

Grant :-)
G Hudson

Someone recently asked about the screw retaining the knob on the direction indicator switch and it turned out to be 5BA. The SU butterfly disc retaining screws are also 5BA.

I was recently at our local model engineering shop getting some BA screws (even number) and I happened to ask if they stocked odd BA numbered screws. The only ones they had were 5BA and the guy there said this was the only commonly available odd BA size and the reason they are commmon is that they are 1/8" diameter.

Even though they are 5BA raised head countersunk they are definitely 'specials' because the raised head appears to be deeper than normal and the slot seems deeper. Also the countersinking angle appears more accute. Finally the thread length is 1/4" long but one half of the end of the screw is split so that the ends can be spread after fitting to prevent them unscrewing.

I'd be tempted to give Burlen a ring and use their stock screws...........................Mike
m.j. moore

If you mean to increase flow through the throat of the carb by cutting the throttle shaft, David Anton of Advanced Performance Technology (APT) in California has the Allen-head low profile screws (he did when I did this several years ago). Cut off the non-threaded half of the shaft, file a knife edge onto the leading and trailing edges of the throttle plate, and screw on the disc with the screws using Locktite. Tyler
C.T. Irwin

This thread was discussed between 25/04/2011 and 30/04/2011

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