The original pony cars were meant to be quick, fast, and good-handling vehicles, and by that times standard, they were. That’s not to say that there are improvements to be made. The stock rear suspension could use a little help in the lateral movement area.
Ladder bar and 4-link suspensions use a panhard bar, which controls the movement of the rear end in a subtle arc. Most people assume leaf springs control lateral movement, but the truth is leaf spring suspensions have a tendency to swing side to side under hard cornering, eventually eating up sidewalls and tweaking quarter panels.
There is a solution however, the Watts link. Originally designed in the 50’s for race cars, the Watts link uses a propeller and 2 articulating rods to keep the rear end centered, so the springs, shocks and tires can do their jobs.
Virtually forgotten throughout the 70s and 80s, it had seemed the Watts link was a thing of the past. Enter Jim Fay of Fays2 suspension. Jim is an avid road racer and during a vintage Mustang race, Jim discovered that several of the other cars had home-made Watts links under the rear. After that, Jim decided to design his own unit and bring it to market.
While most of the Watts link units available seem to be cobbled-up weld-it-yourself version, the Fays2 Watts link is a very nice piece. The unit requires no welding and is a very simple bolt on application. Installation consists mainly of drilling 4 holes in the frame, and potentially 2 in the trunk floor. The supplied instructions are put together well, in a nice spiral-bound notebook, but they are a little hard to follow, and at the end there is an addendum that tells you to put everything together in a different order, which was very confusing. In the end, we used the addendum (there is an obvious reason it is there), and everything bolted up and adjusted nicely.
The kit is supposed to line up with 2 of the gas tank mounting bolts, but one was off a 1\4”. Our car had been hit in the rear many years ago, so that probably accounts for the discrepancy, although the manufacturing tolerances back then could have been off that much anyway. Another note, the instructions call for removal of the gas tank, we did not find that to be a necessary step. We also had some difficulty understanding exactly how we were supposed to drill the inner frame holes from the inner side of the frame. Even with the gas tank removed, there is no way (at least on our car) to get a drill (we tried with a regular drill AND a 90-degree head drill) in the appropriate area and drill using the supplied drill guide. We had to very carefully drill the second smaller hole on the inner frame rail from the outside. After calling Fays2, we discovered that step to simply be a misunderstanding in the instructions wording, which Fays2 has altered.
Other than a few technical problems, everything went pretty smooth. The installation took about 6 hours. We were using a floor jack and 2 jackstands, things would have certainly been a little easier if we had a lift. The results are pretty astounding. When cornering, the car feels like it is on rails, there is no more chirping, the body roll was reduced, and considering the price tag of $595, I’d say it was money well spent. As a side note, the suspension on this car is 100% stock, using the original bushings and springs. We had installed new shocks a few weeks prior. The only mod to the drivetrain was the 3:73 gears and 9” we installed awhile back. The Mustang would get sideways at every turn at half throttle with the steep gears, but after the Watts link, it hugs the corners tight, and with no tire shred. Straight line performance was also improved as the car hooks up much faster with no wheel hop. This is the only rear suspension upgrade a vintage pony needs.
1. The Fays 2 Watt’s link kit comes with everything you need to install the unit in the car. Before you get under the car though, you will need a few tools. Most of the tools should already be in your tool box, but most folks don’t have 1 1\8” and 1 1\4” wrenches and sockets. These can be rented at your local parts store, so don’t stress it too much.
2. The first step is removing the exhaust. The Fays 2 kit sometimes requires altering the exhaust tubes over the rear end, so we just removed both and had them re-routed afterwards. Make sure you jack the back end of the car up with the front wheels chocked and use jackstands.
3. The Watt’s link bracket was test fit to see what needed to be moved or altered.
4. This shot shows where the bracket fits to the car. This is the lip in front of the gas tank. The clips can stay, but the wire that was clipped to it had to be moved. The hard line for the gas tank required some tweaking for the bracket to fit up to the car.
5. The Mustang had been rear-ended a few years back. The floor pan was bent up and had to be beat back in to shape with a mallet for the bracket to fit. We also straightened out the lip as best we could. Not much room to work under these things.
6. The mallet came in handy to knock the bracket in place.
7. The 2 holes that the bracket is supposed to line up with in the trunk floor had to be opened up to match the bracket. This was most likely a product of the wreck. Note the mangled edge of the lip. The instructions say the gas tank needs to be removed, but that just isn’t necessary.
8. The supplied grade-8 bolts and washer were loaded into the modified holes through the trunk floor.
9. Then the Nylock nuts were torqued down from underneath.
10. The side mounts were a little tricky. The kit comes with a brass drill guide that taps into the holes in the bracket. You only use one hole per tab, for our car, the lower hole was used.
11. Then the frame was drilled using a 3\8” drill bit. Drill through the other side of the frame, keeping the bit level.
12. Removing the drill guide, you will be left with a hole smaller than the bracket, which is what you want.
13. The outer frame hole is then drilled with a larger 1\2” bit. ONLY DRILL THE OUTER FRAME RAIL!
14. For the rear bracket mount, a right-angle drill is needed. The same process is performed here.
15. Using the supplied shims, the outer frame bracket and frame rail are aligned. You don’t want the bracket bending, so the space needs to be filled up. We painted ours black and then installed the ones we needed.
16. The special bolts are designed to push through the frame and the shoulder hits the inner frame rail. This keeps the link stationary and does not allow the bracket to slide side to side.
17. The bolts are torqued down.
18. The driver side leaf spring clamp was replaced with this unit supplied in the kit. The lower torsion bar was pre-fitted.
19. Using a square, the distance from the center of the propeller mount to the center of the driver-side torsion bar mount was measured.
20. That measurement was then translated to the passenger side axle tube and the tube was marked.
21. The brake line bracket was in the way, so we used an air hammer to remove it.
22. The axle tube bracket was mounted, keeping it centered on the measurement we made earlier. The tube needs to be parallel with the ground, so we used a level to ensure that.
23. The propeller bolt was placed in the 4th notch on the bracket. The will be adjusted as the alignment process continued. Ours ended up in the 3rd notch once everything was set.
24. The propeller should sit cocked at 5 o’clock and 11 o’clock, with the supplied spacer in between the bracket and the propeller.
25. The driver side torsion bars need to be measured with the propeller in the correct position, set to the correct length, then removed, and the other bar set to match. Both bars are then installed and adjusted so the bars are parallel. That’s it, the install is done. Now go try some corners; the rear tires will be glued to the road.