fuel filling

Hi its been a while but thought I would put the question up.
My 40 build started back in 2000 and ended in 2010.
I made nearly all the components, the only bug I have is filling it with fuel.
I was a motor mechanic for 45 years so you know how things should be made or designed.
I think the breather maybe to small but I would like to know what you guys run.

My course of action so far.
My filler tubes did not have what I thought where ideal bends, so I made a new tube including the cap and pot assembly that sit up the top.
The breather tube is 19mm, it sits next to the filler inlet on the top of the tank.
On the inside a tube has been attached to the breather and goes to the rear of the tank ( a recent mod).
The baffles are not air tight so fumes can spill over the top.

Filling is way better up to about 30lt, with the new set up I can look down inside the filler and it is filling up very easy, like turning a drink bottle upside down and its gulping .
I spoke to my dad about it and he made a suggestion of putting another breather in the bend as per drawing.

So before I do any more I thought I would ask for some suggestions from you guys.


  • CCF_000221.pdf
    223.2 KB · Views: 155
Last edited:
Hi Jim
Long time, no hear. Hope all is well.
I have the same issue and think it’s were the breather re-enters the fill pipe. I can’t get the nozzle down past the breather due to the first sharp bend in the fill pipe and it blows back if I give it beans. Extending the breather tube up inside the filler to just under the cap should stop blow back, but may vent fuel if you are on a slight uphill while refueling.
Not sure if you’ve fixed that on your redesigned filler tube.
Adding a second breather midway in the filler tube may cause turbulence in the fuel flow and backup the flow??

hi Clayton
yes that is what I thought at first, My fill hole that the nozzle go's in was only large enough say 25mm.
I thought ok fumes are not getting out around the nozzle so I opened it up to 50mm and I can get the nozzle in below the breather know.
I have never been able to see inside until I opened it up.
After about 30lt it fills up very easy, considering the pipe into the tank is 50mm I did not think it would be such an issue.
After 30lt I think an air spring is trying to force its self out the filler tube.
I was thinking about running the breathers left to right, so when you fill open the lid on the opposite side to vent the tank you are filling.
I could do a dummy run by disconnecting the vent hoses altogether and see what reaction I get before making changes

I will keep playing. Im not going to let it go as I am curious know.


Ian Anderson

Lifetime Supporter
Your picture looks very similar to my old car. Only difference mine had the breather about half inch diameter within a couple,of inches of the filling pipe which was around 2 inch diameter. As you say the first part of the fill is great and after that it would spit fuel back out the breather. I just learned to live with it but the last quarter of the tank height took a lot longer to fill that the first 3/4 of the tank!

I never did find an answer but did think that perhaps a baffle in front of the breather pipe directly under the cap, which sends the spit back down the filler pipe along side the fuel nozzle would work but I never manufactured anything todo so!

if you look to modern cars fuel tank, most of them having the filler neck going in to the tank at the lower (under) part of the tank, so when you fill up from under the fuel chases the air to the top where the breather is situated, and the filler neck has also his breather , and turbulences are mostly away and filling up is normal,
dont know the work to modify fuel tank from gt 40(replica) it really efficient not