Prototype To Production

My last post showed my ‘homework’ for a prototype part kit I was going to install on my car. I mentioned a while ago to Adam at Mustang Maniac that on longer journeys it would be nice to have a little more legroom. He said that had been asked about it some time ago as well, but there wasn’t really anything on the market. Until now that is, those discussions with Adam have been ongoing and he has had a prototype developed by his engineers. We then discussed how this was going to be done, the original plan was to do some filming of the fitting for their YouTube channel, we decided on a slightly different approach to the original plan for now. Two reasons, the first being the UK’s protest morons that have made getting fuel difficult in some parts of the UK. The second was ‘how difficult would the kit be to fit at home without professional workshop equipment?’ The challenge was accepted, fit the rails at home and share my results with Mustang Maniac while saving myself a fist full of dollars in fuel costs and time.

The seat extension runners came from Mustang Maniac. They are designed to allow an additional 2″ or 4″ movement backwards of the seat for additional legroom while still allowing the seat to adjust on the original runners. These runners are made from a heavy gauge steel with threads and cut-outs which allow for a straightforward installation. These extensions bars will fit all Mustang models from 1964 to 1968 by the way.

From my last post here the rails are dried and already painted with satin black ready for fitting.

There are four studs provided with the extension bar kit to allow the repositioned seat to be bolted back into the car without having to cut the floor pans or seat base.

Depending on your preference of course, you could respray these bars to match your interior as they will be a little more visible from outside as the seat will sit further back on the seat base, but not noticeably so. Satin black is always a good starting point and goes with pretty much everything.

Removing the seat.

Under the car there are four rubber grommets (or should be four) in place where the seat rail studs come through the seat base.

Remove the rubber grommets and inspet the inside. If all is good the studs won’t be correded up and will be easy to remove. If the rubber grommets are missing, or there is corrosion on the studs, then you may need to spray a some WD40 (or similar) to help loosen them up and remove. Make sure to use a good quality socket, if you round the fasterners off then you are in for a whole heap of hurt.

Tip:

Fold the back of the chair forward to the seat base as if you were getting out of the back seats. This helps to balance the weight of the seat and allows the fasteners to be removed without the chair tipping back making removal difficult or even bending a seat stud.

Use a deep reach socket to undo the fasteners.

With all four fasteners removed the seat should lift directly upwards out of the car. Notice in the left-hand pic that the seat falls naturally to the rear. Keep the fasteners safe as they will be used again to refit the seat back into place.

With the seat out, now would be a good time to inspect the seat runners and clean the runners up if needed. Apply a little grease to keep the free movement.

Fitting The Extenders

The bars have to be fitted to their correct left or right hand sides and the right way up. Looking at the seat from below the right hand side has the seat movement handle and a extending bracket. This side will need the cut out sectioned runner to be fitted, as the pics below. You can either attach the studs at this point or later the choice is yours. I prefer to do it later so nothing got in the way.

You will notice that there are holes, recessed holes and threaded holes. The standard holes are to allow flush fitting of the bars to the seat rails where the rivets are. The recessed holes allow for the original seat studs to be held flush to the bar. The threaded holes are for the studs position where you want the actual length of the extension to be.

Below shows the third hole down which is recessed and where the original seat stud(s) will go through.

The top hole is the 4″ extention the second one down is the 2″ extension shown in Red.

Yellow shows the location for the seat rail rivets.

Teal colour shows the seat stud holes.

From the position above turn the bar over to fit onto the seat rail flush. Fit the rail over the original seat studs and use some nuts of the correct thread on the seat studs and tighten the bars firmly into place.

You will now need to cut the original seat rail studs flush with the top of the nut. This has to be done in order to fit the seat back into the car and be bolted back into place. Before you do any cutting, make sure that the seat can still freely move with the seat adjustment handle with the extension bars bolted in place.

You can either mark the studs for cutting and remove the fasteners and bars away from the seat, or do it with the bars still bolted in place which is easier to be honest. I used a Dremel and a thin cut off wheel. Take your time and use goggles in case the cut-off wheel breaks or sparks fly. Going old school with a hacksaw will work just as well. You can see my Dremel in the right-hand picture bottom corner. I also got pretty OCD about it and ground the studs perfectly flush with the fastener.

Fitting The Studs

These new studs have a collar a quarter of the way down. The shorter thread screws are fitted into the extension bars, the longer thread will be going back through the seat base using the original holes.

I painted the top of my studs to match the bars so they were less visible from the outside, just because I could.

You will need a locking pair of grips to screw these replacement studs into place tightly, or a strong hand grip an pliers. I also used a little thread locker to keep them in place. The left-hand picture shows the correct stud fitting.

As I said earlier, if you want the full 4″ extension use the top threaded holes, for the smaller 2″ extension use the second hole down. Fit the second stud at the bottom of the rail extension use the threaded hole just above the larger hole (for the rivet) for the 4″ extension, and the 2″ threaded hole is below the larger hole. See the marked up image earlier on the page. If you are in any doubt measure the original seat stud gap and apply the same gap to the 4″ or the 2″ stud holes.

Refitting The Seat

Take the seat back to the car and drop the studs through the original holes in the seat base and carpet holes. From there screw on the fasteners from underneath the car to hold the seat in place. Refit the carpet spacers and then tighten up the seat properly.

Replace the rubber grommets and the job is done. I sat back in the car and was amazed at the difference that the extra few inches of leg room gives you. For a 6’4″ bloke like me I was always a little crunched up on leg room, that little bit extra makes it so much nicer to drive. Also as the seat base actually slopes down towards the back of the car, in effect I have also gained a little more headroom too. Win/win all round then. 🙂

The fitting was straight forward and I reported my work back to Adam with the photo’s. He has now decided to go into production with the current design. Their measurements were spot on so no need to make any modifications. I suspect they will be on the Mustang Maniac WebShop Soon, along with some of the photos and description of the fitting.


The second part of the my little upgrades I promised was the hood springs. There was nothing wrong with them at all, except that Adam showed me a set he has just fitted to the project car they have in a workshop. I see them, I wanted them it was a simeple as that. Not the cheapest replacement part just for looks, but why not? These springs are super strong and will have the Devil’s bite on you or the car if you get it wrong when replacing them. I packed an old duvet cover around the hood springs and levered of the springs carefully and under control with a large screwdriver come crowbar. They were replaced in a matter of seconds. I was so worried about the springs pinging off and damaging the paint or parts under the car, or flying up and removing part of my jaw that I forgot to take pictures. I do have the before and after pics for you. Most people wont even notice the change and think they are stock parts, but I think they just add a little bit of something extra to look at.

Right hand side:

Left hand side:

The last part of the day’s work was the annual oil and filter change. I tend to do around two thousand miles a year at most. But, I would rather pay £35 for fresh oil just to be on the safe side each year. The K&N gold oil filters I use are a bit bigger than the standard Ford oil filters, which means that I have to put in more oil in than the standard recommend five US quarts to get the levels right.

Now I’m all set for the car show season, apart from a quick wax and once over that is! Lets hope the weather stays fine for the shows. I will let you know as the season goes on.

Share my Content