Background:
Classic Mustangs and most other cars of the era were fitted with a fuel filler pipe that was quite a big diameter. At the time this made sense for the larger fuel pump nozzles with a bit of extra space too. With the onset of unleaded fuels and then the devils own juice of Ethanol diluted fuels, the nozzles got smaller but with increased pressure. Modern day cars are fitted with smaller necks and anti syphon etc. which doesn’t have any problems of the fuel spitting back out when full.
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 efficiently enough. This means the fuel is allowed to backfill up the neck and splash back out over the car and yourself if you stand in the wrong place. Eventually this will cause staining and remove any protection you had on your paint.
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 the filler pipe is a mod where an anti splashback valve is fitted. The valve is designed for the unleaded fuel pump nozzles of today 13/16″ and will stop the splashback problem.
Filling up now I tend to go through the same old routine of getting a microfibre cloth, laying it over the bumper ready for the inevitable splashback if I want to fill 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. The finish is excellent looks great in the trunk, not that many people will ever see it.
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. This is perfect when additives could be used and allow a trickle flow of fuel to run through the valve.
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 add some more 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 the metal filler pipe flange to the paint. Also the filler cap will sit just a little further way from the paint which helps avoid the scratching the paint when fitting the cap back onto 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 from the rubber hose. Turn the pipe back to the correct position and then you can simply press down the rubber hose to the fuel tank.
Align the filler pipe neck to the rear panel, once the hose and pipe are in place and aligned add the screws to hold the pipe’s flange into the panel. I started by adding the anti theft bolt through the gaskets and the panel as this does not have much adjustment. 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 facing the inside of the trunk, this mean that things like cloths would catch the bolts and is incorrect, I never got round or had the need to disturb the rubber and clamps until now.
The clamps should be between the filler pipe and the rear panel and so they will be out of the way. The photos below show the correct positioning. Lightly tighten the clamps just to hold them in place for now.
Final alignment of the gasket(s) up to the panel holes and add the rest of the screws/bolts to the filler pipe flange and gently tighten up to hold in place ready for any final adjustments.
With the screws/bolts all in place and you’re happy with the alignment, start to tighten the fixings 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 as the wire is in the way.
Tightening the flange fixings 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 any slight differences of alignment between the tank and the new filler pipe.
Results:
Brilliant. The filler pipe was a like for like swap, now I have little bling in the trunk too. The nickel plating looks great as well a hidden practical functionality. I have now also reversed the hose clamps which was something which had annoyed me on the odd occasion.
From the outside there is no difference to see. But on the inside there is something to stop me getting my regular splashback on a 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. See ‘Update‘ below.
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.
Where To Buy:
These are now available in the UK via the sole supplier Mustang Maniac, by the time you have paid the shipping and import duties it will work out about the same cost. The link for this higher end nickel plated version is here. Or cut and paste this to you browser: https://mustangmaniac.co.uk/part/64-66_Splash_Back_Fuel_Neck/15517
Update: ongoing
Excellent!
I have filled the tank up until the fuel nozzle cut off is activated and NO splashback. Whether I fill up till the nozzle cut off click or just a short fill, the filler pipe has performed flawlessly. I have also always used Castrol Valvemaster Plus fuel additive with every trip to the petrol (gas) station. The additive is added on a per litre which is tipped into the filler neck before the fuel goes in to mix correctly. The original design of the neck and the valve still allows the additive to flow down into the tank and not pool up at the valve. To properly mix the additive with the fuel, I poor the additive first, then trickle some fuel down the neck to flush the additive fully down into the tank, after a few seconds I fully insert the fuel nozzle and fill as normal.
Adding the fuel additives and the fuel itself has been perfect each time no matter where I have filled up. I still lay the microfiber over the bumper, but that is only to catch any drips from the nozzle and not needed now to mop up a mess.
This is upgrade is seriously a game changer and money well spent.