Just for the record, the British Association or BA thread system was extensively used in the electrical engineering field in the UK before they decided to go semi- metric. A 0BA thread has the same pitch as an M6 x 1.0 but the BA thread has an included angle of 55° vs the 60° of the metric M6.

I did all the checking I could and do believe that they are BA screws. I ordered a handfull of the bolts, nuts and washers from a supplier in the UK. The various SU parts guys have a heck of a mark up on them. I ordered enough for 10 cars worth since shipping was like 25% of the total cost.

Thus I will double check them when they get here but I will have extras if someone needs some. There are a number of them missing from the carbs in my boneyard, thus my need.


Chris

These guys sell SS screws:

http://britishclassicmotors.com/3322.html

Or MossMotors www.mossmotors.com sells the screws individually.

or from the manufacturer:

http://www.sucarb.co.uk/productDetail.aspx?id=30790

or google up Joe Curto.

Size is British Association... not metric but not UNF or UNC either.
--
Mike!

Edit to fix BA reference and spelling.

Actually it sorta is - see Wikipedia on British Association Screw Threads.
Here is a table of them (if it copies):
BA Outer
Diameter Threads Threads
per inch per mm Tap drill
0 0.2362 in / 6 mm 25.38 1 5.1 mm / 7 gauge
1 0.2087 in / 5.3 mm 28.25 1.112 4.5 mm / 16 gauge
2 0.1850 in / 4.7 mm 31.35 1.234 4.0 mm / 21 gauge
3 0.1614 in / 4.1 mm 34.84 1.372 3.4 mm
4 0.1417 in / 3.6 mm 38.46 1.514 3.0 mm
5 0.1260 in / 3.2 mm 43.10 1.697 2.65 mm / 37 gauge
6 0.1102 in / 2.8 mm 47.85 1.884 2.3 mm
7 0.0984 in / 2.5 mm 52.91 2.083 2.05 mm / 46 gauge
8 0.0866 in / 2.2 mm 59.17 2.330 1.8 mm
9 0.0748 in / 1.9 mm 64.94 2.557 1.55 mm
10 0.0669 in / 1.7 mm 72.46 2.853 1.4 mm / 54 gauge
11 0.0591 in / 1.5 mm 81.97 3.227 1.2 mm
12 0.0511 in / 1.3 mm 90.91 3.579 1.05 mm

So it looks like your screw is probably a 4BA screw.
Note that NONE are close enough to be interchangeable with
either US or metric machine screws.....
--
George Downs Bartlesville, Oklahoma

Jim Taylor told me that the screws on older SU carbs are "British Association" threads.
Best bet is to scarf a screw from one of the carbs in your culch heap.
I'm sure that Joe Curto and Rhys Kent have them.
--
George Downs Bartlesville, Oklahoma