Saving Old Seagulls

I've had this oddball steel tank on the shelf for some time, with a non seagull screw cap, the plan is to convert it to a bayonet cap. I've no idea about the history of the tank, but it does seem to be a seagull one. I've now got all the parts I need to do it. A NOS Ceandess filler neck and also new cap from Ceandess which are still made in Wolverhampton, since 1924. I drilled the cap and made a new vent valve some time ago, as part of a small batch, including some dummy valves which look identical to a functioning version.

The same guys who made the original seagull parts, and also fitted to many classic british motorcycles, lawnmowers, cars etc.

https://ceandess.online/

Are you going to braze it on?

I would soft solder it, should be strong enough.
Or perhaps low temp silver solder https://www.cupalloys.co.uk/low-temp-silver-solder/

My first thought was to soft solder it, I’ve got a nice small nozzle to get the heat just where it’s needed. I’m not sure what the steel is like under the thick paint though. It will be a while before I get to it. Just getting parts together at the moment.

Your first task should be find out how the previous neck was held in, that might limit your choices.

The previous neck is thinner, so I’ll be able to just cut it out and then machine a hole to fit the new neck perfectly I hope

I had a restoration to do on a total wreck of an engine, the petrol tank had no cap but someone had tried to fit the bayonet type, off a radiator no doubt.

I had an egineer make a new neck up for me.