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Discussion Starter #1
Anyone know what size and thread the fuel inlet banjo bolt is on the early SU carbs (mine are 72's). I have tried 1/2 inch NF20 and that is as close as I can get. 1/4 NPT is close too. Is it some kind of Whitworth thread? 12MM is too tight.

The housing is likely to tight for me to attempt tapping it out. It would likely break the aluminium housing.

I am plumbing my fuel system with AN6 fittings and braided hose (holley fpr, russel fittings, holley performance fuel pump by the tank, russel billet aluminium filter, russel whiteface fuel pressure gauge). I would like to plumb it all the way to the carb inlets without having to use those ugly worm clamps.

If I do have to tap it - it looks like 1/4NPT is the best way to go.
 

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If it is that close to a 1/4 NPT it is likely either 1/4 BSP or BSPT. Call 1-800-272-7537 (1800CPARKER) for nearest regional sales office for Parker Fluid Connectors. They have adapters for BSP to NPT and SAE connections. Look at F3HG, F3HG5, F40HG5, and F40HG fittings, on pages H28 and 29 of January 1999 catalog # 4300. Hope this helps you. Looking at my carbs I believe that they are BSPP fittings (parallel not tapered) since there are seals on both ends.
 

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Discussion Starter #3
I must say I have never heard of a BSPT before. Some kind of British standard I presume. I'll look into it. I suspect I will just be attaching to the existing fittings with hose-clamps until I can get this figured out.

Thanks for the info.
 

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Yup. British Standard Pipe Parallel and British Standard Pipe Tapered. They are the same DIAMETER as American NPT fittings but the thread pitch is different. Just enough different so that NPT won't work. I have run an NPT tap through some of the fittings (such as the old holes where the air injectors went on the exh. manifold) and then used NPT plugs but that was only when I was pretty sure I was not going to take them out again. Then I used thread sealant and ran the plugs in. TIGHT !!!! I don't ever want to try to remove them! :-o BTW the BSPP and BSPT are the same as a JIS PT and PF fittings (Japanese Industrial Standard -Pipe Tapered and Pipe Straight). They were used on a lot of the Japanese vehicles of this era. Same fittings, different spec name. But what you can ususally find adapters for are the British named sizes.
 
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