Early and later fuel tanks - options

[Carboy0]

I am doing they Round Britain Reliability Run in October, the ROM shows that pre-1973 Stags had a 14 gallon fuel tank and 1973-on Stags have a 12.75 gallon tank. My 1973 Mk2 Stag has the smaller tank. My question is whether the larger tank can be retro-fitted to my car?

If yes how can identify an early tank and are they available new (and where) or only used?

[richardthestag]

Maybe you are looking at US Gallons and IMP Gallons?

I didnt realise that there were different fuel tanks for the stag

[Carboy0]

Fair question, but the ROM definitely shows two different size tanks and both definitely imperial, as they list the US gallonage separately. Check page 09-2 in the ROM, the section on Capacities at the bottom of the page.

[Lingen]

I think all tanks were the same physical size, but at some early stage the end of the filler pipe was made to go deeper in to the tank..This created an unfillable air space in the top of the tank, reducing its "Capacity"
I believe it was done to cure the problem of a full tank of cold fuel expanding all over the road when it heated up in hot surroundings. I would avoid getting one, and carry a spare can or two in stead!
Mike.

[Carboy0]

Ah, that explains a lot, thanks. I saw just that happen on another classic a couple of years ago.

[mole42]

I did the RBRR in 2016 in my Stag and didn't run low on fuel anywhere.

[Carboy0]

I was hoping to extend the distance between refills by using a bigger tank.

[mole42]

Bigger tank is only about 30 miles and the Organisers have provided adequate fuel stops.

[Carboy0]

OK thanks