Uuumm - no..  The filler neck from your link is a fake.  It provides the "Cooper" twin tank look without the hassle of actually fitting a second tank.

The Monza cap seems such a great bargain ($39??? - compared to the "Aston" styles advertised for $79...) that I wonder if all is kosher..

The neck A2A referrs to is the little brass tuby bit shown in the Monza ad.

As the Monza ad states, the tank neck is 2 1/4 inches...  Monza - and Aston - caps are available in chrome or alloy ..and vented ..or not...

Cheers, Ian

That's the one I was eye balling but haven't measured my tanks neck. I don't think it's 3 inches... Did you have to buy this filler neck?

yes, definitely, install a tube on your tank vent and route it to the outside of your car

the fumes are dangerous to your health and if any spilled inside of the boot (battery is back there) it could be worse

Norm

jzj88 after losing two caps I got the Monza Repro that I just love, just flip it open and closed:

//www.minimania.com/part/SP228/MONZA-CHROME-GAS-CAP-WITH-COLLAR

However the brass threaded coupler is a very tight fit.  I hit mine with the heat gun to get it on and even so was not able to pound it all the way on and pointed the right direction.

About the fuel tank vent, thanks Doug, I was wondering if a vent tube was originally attached to the top of the tank. My whole car smells like gas - badly - after filling up.  I was worried that a vent tube would siphon gas out after filling up, but your description seems to indicate that's not a worry.

Mousy

Most carbureted Minis have vented tanks and can use either cap type.  To determine what your car has, open its boot and look at the top of the tank right below the horizontal body panel behind the back seat.  If you see a 1/4" diameter plastic tube coming off the tank and going down through the boot floor, your car's fuel tank is vented.  If the tube is missing you will see a small diameter tube nipple sticking out horizontally pointing towards the middle of the boot.  With the tube missing the boot should smell heavily of gasoline.

The vent allows air into the tank as you drive.  If your car had a non-vented tank and used a non-vented cap, then as you drove, the drop in fuel level would start to create a vacuum in the tank.  Eventually that vacuum would equal the ability of the pump to "suck" fuel and the pump would stop moving fuel to the carb.  Eventually the engine would stop from fuel starvation.  

As their names imply, a non-vented cap has no air hole to prevent the vacuum from forming  while vented caps do have a hole.  If you have a vented tank you can use any cap you want  However, a non-vented cap is less likely to slosh fuel out onto the paint work if the fuel level is high.  As the product descriptions mention in the web links you posted, injected cars handle emissions and fuel delivery differently and require a non-vented cap.

What is the difference between vented and non vented petrol caps, and Which petrol cap should I get, all of these look the same and I don't really understand the mambojambo.... I have a 80's mini... 1,2,3 Thanks for your input...