There are certain aspects of building a race car or fast street car that directly affect the car’s performance, like the engine, transmission, and rear gear. But there are other aspects that affect the car in a more indirect way. Parts like lightweight wheels and fiberglass body components can help make a car quicker by shaving pounds from the vehicle. But other items like aftermarket axles, a driveshaft loop, and frame connectors actually add weight to a vehicle. Parts that add weight to a car are often necessary in the interest of safety, or required by racing sanctioning bodies, but some of these parts, like subframe connectors, offer benefits that "outweigh” (no pun intended) the pounds they add to the vehicle.
If you’re a regular reader or subscribe to Mopar Muscle, you’ve likely been following along as we put together a ’64 Dodge Polara, that will first be used as a fun street/strip car, and then evolve into a dedicated drag car. Eventually, our Dodge will compete in the Nostalgia Super Stock class of drag racing, and perhaps even run in the Nostalgia FX classes if we get the car to run single-digit elapsed times. So far this has been a fun project, and we’re building the car like many of our readers would, by getting it running and driving, then upgrading the car as we have fun with it.
When we purchased this Dodge, it was somewhat of a basket case, but through hard work we’ve put it back together, adding high-performance suspension components from Calvert Racing, disc brakes from Wilwood, and differential components from Strange Engineering. We’ve also installed a powerful big-block, topped with Indy 440-1 cylinder heads and a race-prepped 727 transmission, so our Dodge should have enough power to run respectable elapsed times at the track. Expecting hard launches from our high-torque engine, we knew we would need to stiffen the chassis of our Dodge, and the best way to accomplish this goal is with subframe connectors.
Nearly all Mopar muscle cars are built with a unit-body (commonly called unibody) construction method. Instead of building the car with a separate frame, and then attaching the body to the frame, unibody construction actually incorporates the frame and body together as one structure. This construction method simplifies work on the assembly line and makes total vehicle weight lighter, but the downside is a sacrifice in chassis stiffness and rigidity.
When used in a high-performance street or racing application, unibody cars can flex and distort, causing chassis misalignment or even worse -- wrinkled or cracked sheetmetal. Early Mopars like our ’64 are even more prone to damage, since they are manufactured from thinner metal in the floors and frames than later Mopars. In fact, most hardtop models like our Dodge, flex enough that the body gaps will grow when on the car lift, and you might even notice the doors don’t open or shut the same when the car is on a lift or jacks. Body flex such as this is counter-productive to handling or straight line performance, and needs to be corrected not just so the car performs better, but also in the interest of safety and durability of the vehicle.
02 Since these frame connectors are welded to the floor, the carpet either needs to be pu
03 We prefitted our subframe connectors and marked the floorboard and areas of the subfra
04 Our Dodge was undercoated from the factory, so we used a propane torch and scraper to
Installing subframe connectors is the most common way to improve chassis stiffness in unibody cars, but most sub-frame connectors only connect the car at the front and rear frame areas. When researching connectors for our car, we found that U.S. Car Tool offers subframe connectors that are different from others. The U.S. Car Tool connectors don’t just tie the subframes together at the front and rear, but are laser cut to follow the contour of the car’s floor, allowing the top of each connector to be welded in place at multiple areas along the floor of the car. This type of subframe connector uses the car’s floor to form the “box” of the connector, and also allows the car’s floor and upper structure to complement the extra stiffening offered by the connector. The end result is a chassis that is far less prone to flexing under the high loads imposed by a big engine or aggressive driving.
U.S. Car Tool offers a variety of products for Mopars, as well as the tools and equipment used during a restoration or car build. Their subframe connectors are designed specifically for the various body styles of Mopars, including early B-Bodies like ours. Instead of being manufactured from standard rectangular or round tubing, the U.S. Car Tool subframe connectors are formed in a U-shape, with the upper edge of each side laser cut to follow the car’s floorboards. While this manufacturing style does add a little to the installation time, the end result is a connector that is attached to the car at the front and rear subframes, as well as along the entire upper surface of the connector. This type of manufacturing not only provides a stiffer chassis, but these connectors are lighter than conventional connectors since less material is used for their construction.
We ordered our connectors from U.S. Car Tool, and had them at our shop in just a few days. Our initial impression of these products was favorable, and they were professionally packed in a way that prevented damage during shipping. Trial fitting the connectors, we found them to fit nicely between the subframes of our Dodge, and also follow the contours of our stock floorboards. Of course if your car’s floors have been replaced, these connectors will only fit as well as the new floor panels since they were designed using a stock car as a template.
06 Final fitting and initial welding of the U.S. Car Tool subframe connectors should be a
07 After tack welding the frame connectors in place with the car on the jackstands, we pu
Even with stock floorboards, we did need to knock down a few high spots on each connector, and had to push the floor down slightly from inside the car to make contact in a couple of areas. This is not the fault of the frame connector, but rather the tolerances of manufacturing, and a nearly 50-year-old car that has seen its share of street use. Using a floor jack to hold the connector in place, we marked the high spots on the frame connectors and traced the connectors on the floorboards to show where they would mount.
After removing the front seat and carpet (to prevent fire, right Randy?) we put the car on a lift and used a propane torch and scraper to remove the undercoating from the car’s floors where the connectors would be welded in place. After removing the undercoating, we used a sanding disc to remove the paint and any remaining undercoating, exposing the bare metal of the floors for welding. With this accomplished, a grinder was used to knock the high spots off the frame connectors. Test fitting the connectors multiple times and making minor tweaks is the best way to ensure a tight fit, and within little time, we had our connectors properly fitted and ready for welding.
To weld the connectors in place, the car’s weight should be on the wheels. To accomplish this and to give ourselves enough room for welding, we placed jackstands under the rear differential housing and the lower control arms to support the car. Once we had the connectors welded in multiple locations at the front, back, and along the floor, the car can be lifted again for finish welding. We “stitch” welded the connectors along the floorboards, welding one-inch sections at a time, working back and forth along both connectors until they were welded along 75 percent of the floor area. It is impossible to weld 100 percent of the area where the floor meets the connector, but just weld as much as you can, and at least 50 percent is recommended.
All told, it took the better part of a day to install our connectors, and after welding and painting the connectors, they look as if they were installed by the factory. Even better, when the car is on the lift, body flex is minimal, the doors open and shut properly, and body panel gaps remain consistent. We can’t wait to get our car to the track and really put the frame connectors to the test. Along with the rollcage we eventually plan to install in our Dodge, these connectors will brace and stiffen our car’s chassis to handle all the power our big-block can put out. Check out future issues of Mopar Muscle as we get our ’64 Dodge to the track for testing! mm
|U.S. Car Tool Subframe Connectors PN USCT1M1111||$169|
|Welding wire and Gas||$4.40|