Background:
Classic Mustangs and most other cars of the era were fitted with a fuel filler pipe that was quite big diameter. At the time this made sense for the larger fuel pump nozzles with a bit of space too. With the onset of Unleaded fuels and then the devils own juice of Ethanol diluted fuels the nozzles got smaller but with now more pressure. Modern day cars are fitted with smaller necks and anti syphon etc. which doesn’t have any problems.
However, back to the classic cars there is a huge annoyance with many, if not all of us owners. When filling up the fuel cut off doesn’t activate fast enough. This means the fuel is allowed to backfill up the neck and splashback out over the back of the car and yourself if you stand in the wrong place.
I spotted a link where somebody had modified a the 64 – 70 Mustang filler pipes. The size was exactly the same as the originals, but inside is a simple anti splashback valve. The valve is designed for the unleaded fuel pump nozzles of today 13/16″ and should stop the splashback problem.
I tend to go through the same old performance of getting a microfibre cloth, laying it over the bumper ready for the inevitable splashback if I top the tank up.
Costs: $110 for pipe + $45 international shipping
Date: 9/3/2025
What’s in the box:
The was just the nickel plated fuel pipe wrapped in a plastic bag, then wrapped in packing paper. I paid extra for the nickel plated version rather than the standard powder coated version.
This is an exact replacement for the standard filler pipe. The only minor difference is the bottom of the filler pipe has a slightly ribbed bottom which should aid in sealing of the hose to the pipe.
The definition of fuel ‘valve’ is a piece of sprung metal behind the reduced filler neck size. There are a couple of breather holes as, two at the top and one where the bottom of the flap finishes almost at the bottom of the filler opening.
Around the neck of the filler where the valve is located are a number of dimples. These are punched into the metal to hold the valve in place. Although these can look unsightly, they will be hidden by the trunk’s closing bracket and will not be seen.
Process:
If you have a trunk mat roll it out of the way to expose the top of the fuel tank. I also have a a sound deadening mat on top of my polished stainless steel tank which is semi stuck down. I didn’t see the need to remove the deadening for this mini project.
Remove the fuel cap. If you have the security version like mine there is a threaded bolt that goes through the filler panel and held in place by a nylon nut. Undo the nut and remove the security wire and the cap.
There will be four remaining screws around the outside of the flange which will need to be removed.
Inside the trunk there is a rubber hose clamped in place by two wire fittings, one to the filler pipe, and the bottom to the fuel tank itself. It’s easier to undo both the top and bottom clamps, the fuel pipe needs to come out of the rubber hose, or pull the rubber hose up of the neck of the fuel tank itself. Either way is fine, you just need to remove the rubber hose pipe completely from the hose.
In my case the hose came off the tank first. With the fuel pipe now free, remove the hose from the pipe otherwise the filler will not go through the panel as the opening is fairly snug.
With the rubber hose removed gently remove the pipe out of the panel. Depending on the age of the cork gasket it may be stuck to the paint or just be stuck to the back of the filler pipe flange, as was the case for mine.
Tip / Warning:
With the pipe removed there is the exposed fuel tank opening. Don’t let anything fall in there such as dirt or nut’s and bolts. I placed my filler cap over the opening which you can see in below left photo.
With the pipe out of the way, now is the time to clean and rewax the opening for protection, if needed. I did just for the sake of it as it wont hurt and also add protection.
Refitting:
The process is the exactly the same but in reverse. It’s always recommended to replace the cork gasket, in my case I used two of them. The additional gasket just helps with the alignment of the filler pipe and also gives a little more protection of metal filler pipe flange to the paint. Also the filler cap sits just a little further way from the paint which helps avoid the scratching the paint when fitting the cap back to the filler pipe.
Add the gasket(s) to the pipe before before feeding the pipe through the rear panel.
With the pipe through the panel it’s easier to fit the hose to the pipe by turning it ninety degrees. Don’t forget the clamps if you removed them. Then turn the pipe back to the correct position and then you can simply press down the hose to the fuel tank.
With the hose now in place add the screws to hold the pipe’s flange to the panel. I started by adding the anti theft bolt through the gaskets and the panel. Add the washer to the front side of the flange, then the the second washer followed by the nylon lock nut on the inside. Don’t tighten it up yet.
Next arrange the clamps how they should be on the rubber hose. When I first fitted the filler pipe and the hose I had the clamps on the inside of the trunk, this mean that things like cloths would catch the bolts. See below right hand photo. I never changed until now.
The clamps should be between the filler pipe and the rear panel and so they will be out of the way. Left and middle photos below show the correct positioning. Lightly tighten the clamps just to hold them in place for now.
Align the gasket(s) up to the panel holes and add the rest of the screws/bolts to the flange and gently tighten up to hold in place ready for final adjustments.
With the screws/bolts in place start to tighten them up and the security wire bolt. Ensure the security wire is aligned with the outer part of the flange, or you won’t be able to fit the cap back back on.
Tightening the flange screws/bolts will pull the pipe into position onto the panel. Now go back inside the trunk to the hose clamps and fully tighten them both up, the rubber will compensate for the difference of alignment.
Results:
Brilliant. The filler pipe was a like for like swap but now I have little bling under the trunk. The nickel plating looks great as well a a hidden functionality. I have now also reversed the hose clamps which was something which has always annoyed me.
From the outside there is no difference to see. But on the inside there is something to stop me getting my regular splashback on fill up. I have noticed over the last few days that there is a reduction in fuel vapours as well in the garage.
Once I have taken the car for a fill up I will give the results of the fill up and if the anti splashback works. It certainly can’t be any worse than what I already have.
Time Taken:
Half an hour in total.
I took an extra fifteen minutes to clean the panel, wax it and add some wax protection to the screw holes in the panel to help keep the rust worm away with the metal to metal contact.