A quality set of sub-frame connectors, that fit like they were Ford designed original equipment, can be fabricated with basic tools skills and a very little money.
Plans for building connectors for a 64.5-73 coupe or fastback. The bottom drawing is the side view and the top drawings are the top view of both connectors D-side and P-side respectively.
“Why do I need sub-frame connectors???”
The Mustang has the heart of a lion with the sleek sporty lines to rival any sports car, but it is built on the chassis of a 4-door family car, the Ford Falcon. In other words, when it comes to chassis performance, specifically in handling, the Mustang has LOTS of
room for improvement. One attribute of the Mustang that it definitely gets from it roots in the Falcon, is the unibody design. Basically, unibody means that the car does not have a solid frame running full length of the car from the front to rear. The lack of a frame is accomplished by short frame rails at the front to attach the motor to and frame rails at the rear to attach the rear end to. Connecting these two sets of frame stubs is nothing more than the body of the car, more specifically the cab. Ford and many other manufacturers used this design because it was cheaper to build and lighter. The problem with this design is that the body must hold its own weight and react to ever changing road conditions. Off of the factory floor, the unibody design of the Mustang worked well, but over the last forty years, daily abuse coupled with rust in key locations, can cause a car to sag in the middle. Even if the car does not sag, if you look at any unrestored early Mustang, you will find a crack at the rear base just below the rear side windows on one or both sides. This is the result of flex in the unibody. One simple fix to improve the overall structural integrity of a Mustang, and a must for any Mustang that is going to be used in performance applications, is to install sub-frame connectors that join the front and rear frame rails, making the frame a solid unit that runs the full length of the car. More details on this topic including a larger picture of the draw out plans and a comparison of many aftermarket options can be fond at
DazeCars, Ford Galaxie Mustang tech and restoration under the heading of
sub-frame connectors.
Before you start this project you need to evaluate your welding skills. The following is the process for constructing a primary part of the Mustang support frame and if your welding skills are not sufficient for the task, catastrophic failure could occur.
NOTE: If you have any doubts AT ALL about your welding skills, DO NOT ATTEMPT TO MAKE YOUR OWN SUB-FRAME CONNECTORS!!
One option for the non-welder is to prep the materials and then take them to a certified welder for assembly and installation.
Tools required:
Cutting tool
Angle grinder
Welder
Angle finder
Tape measure
Materials required:
2” x 1/8” plate steel, about 4 feet
2” square tubing 1/8” walls 8’
Fabrication Process:
The first step is to cut two 4’ pieces of the 2” square tubing.
Once the pieces are cut, they need to be marked at the points where the connectors need to be bent. I made the marks on all four sides of the tubing at all four bend locations. The first measurement is 6.5” from the front, the second measurement is 12.75” from the front, the third measurement is 25.75” from the front and the fourth measurement is 35.75” from the front, which should leave 12.25” from the last measurement to the end of the tubing. Each one of these measurements is going to be a bend in the tubing. Once you have the original measurement marks, additional marks need to be made so that notches can be cut out of the tubing.
Further down the article where we get to the point where the notches have been put in and the tubing has been bent, the final result of the bending needs to be that the first and third bends are 174 degrees and the second and fourth bends are 170 degrees. The first bend needs to be down, the second bend needs to be towards the outside of the car, the third bend needs to be up and the last bend is towards the inside of the car. I mention this now so that you know which side of the tubing to mark for cutting.
To best achieve proper angles and consistency, two things need to happen. The first thing is that the correct wedges of material need to be cut from the tubing and the second is that a jig needs to be made to ensure uniform angles. When it comes to the proper wedge thickness being removed, the 174 degree bends need to have about ¼” of material removed from the inside of the bend, and in the same way the 170 degree bends need to have about 3/8” of material removed from the inside of the bend. To achieve this I split the distances, either ¼” or 3/8” depending on the bend I was working on, putting lines on either side of the four bend marks I had already made. I then drew angled lines from the edge of the lines I had just made to the centerline on the outside of the bend. NOTE: on an individual connector, the first and third bends need to be opposite of each other, as do the second and fourth bends. When comparing the drivers side and passengers side connectors, the first and third bends will be the same on both connectors, however the second and fourth bends need to be mirror opposites of each other. It is the second and fourth bends that determine whether or not you are making a drivers or passengers side connector.
Once the wedges have been marked, the wedge needs to be cut out. This can be done several different ways ranging from a plasma cutter, chop saw set at an angle, a cut off wheel or reciprocating saw. It is important that when cutting the wedge you DO NOT cut through the bottom side. For best results cut down to the inside of the wall on the bottom side. Once the wedge has been cut out, I recommend grinding an angle on the cut edges to insure proper weld penetration. Also, grinding the edges makes it so that when the edges come together they form a trough, which allows the welds to not protrude very far past the surface of the steel and if one chooses to grind the welds smooth after the connectors have been finished, most of the weld bead will remain intact. Before the connector has been bent and welded, I recommend cutting a 45-degree angle on the bottom side of the connector in the end to make a smoother transition to the rear frame rail.
Once the steel has been prepped, it can be placed on two sawhorses, with the top of the wedge up and then pressed down to the correct angle, closing the wedge and then tack welded into place.
When bending the steel, for best results, the sub-frame connectors MUST be identical in retrospect to the corresponding angle on that connector, as well as the corresponding angles on the other connector. In other words, for best results, the four 170 degree bends (two per connector) need to be identical, even if the bends are + or – a degree, you want all four bends to be exactly the same (same thing applies to the 174 degree angles). The easiest way to achieve uniform angles is to build a jig out of a scrap piece of 2” high wood or steel that is firmly connected at the angle you want and long enough to sit across the saw horses. That way the jig and the connector you are working on can be placed side by side on two saw horses and the connector you are bending can be bent to match the jig. Obviously, two different jigs will need to be made since there are two different angles. To build said jig, place the steel tubing or wood in a chop saw, set the saw at 5 degrees off of 90 for the 170 degree jig and 3 degrees off of 90 for the 174 degree jig. Then take one of the cut pieces and rotate it 180 degrees and then match its face to the face of the other cut piece so that they can be lined up to achieve the desired angle, and firmly attach the two pieces together via welding or glue, depending on the material you are using. Once you have the jig, place the notched connector next to the jig and bend the connector, closing up the gap. The connector needs to be bent to the point where both sides are parallel with the two parts of the jig, and then tack weld the notch opening.
If there is a slight gap between the two sides, it is not a problem because the gap can be welded closed. After tack welding the bend, double check again and make sure the jig and connector are the same and that the correct jig was used for the bend. Once the bend has been deemed accurate, you can weld it closed.
Once all four bends have been made, the only thing left to do is attach a cover plate on the back angled cut which measures 2.5” long 1/8” thick and 2’ wide, two side attaching plates on the end which measure 3” long 1/8” thick and 2” wide and two spacer plates on either side in the front which measure 6” long 1/8” thick and 2” wide. The end plate needs to be positioned over the angled cut end and welded up on all four sides so that water and road debris cannot get inside the connector. The attaching plate closest to the front of the connector needs to be 5.5” from the last bend with 1” of material on the connector and the second attaching plate needs to be ½” from the first. I use two plates rather than one large one to have more surface edge area to weld to.
The spacer plates on the front are spot welded in several locations.
The connectors are now finished and can be installed using the following instructions.
Installation Instructions
1. Make sure that the car is sitting in a normal level resting position when the connectors are installed with full weight of the car on the wheels.
2. Drill two 1/2" holes in each front frame rail (centered vertically and at a distance of 2” and 4” forward from the back cap of the front frame rail).
3. Remove the rear caps on the front frame rails on both sides by cutting them with a cut off wheel.
4. Insert a sub-frame connector into its corresponding front frame rail so that the two side mounting spacer plates are almost completely inside the front frame rail. Support the sub-frame connector, then mark the front and rear frame-mounting locations on the car to indicate where the sub-frame connector will be welded to the original frame rails. Remove the connector so that the front and rear mounting points, that have been marked, can be cleaned and prepped for welding.
5. Once the original frame rails are prepped for welding, reinstall connector and tack weld the rear first. Make any adjustment required for best fit and tack weld the front.
6. Repeat steps 5 and 6 on other side, making sure both connectors are located in the same position only a mirror image of each other.
7. Once you have both sub-frame connectors in the desired location, plug weld the two ½” holes on each frame rail and weld up the gaps between the sub-frame connectors and the front frame rails.
8. Weld around the rear mounting locations, including several welds on the outside non-bracketed section where the sub-frame connector meets the rear frame rail.
Installed P-side connector
Today
