In our last installment on “Scarlett,” our 1972 coupe project car, we started setting up the front suspension to make the car handle better, adding a heavier Addco sway bar and coil springs from Muskegon Brakes. We also installed Energy Suspension bushings to keep everything moving without excess deflection, along with 17-inch alloy wheels from Summit. The latter were shod with 275mm-wide BFGoodrich tires in place of the 215s the car came with. Having greatly improved the available grip up front, it was time to get to work on the rear.
Before we get into the how-to part, a word of caution: This is dirty, tedious, physically demanding work. It’s hard, it’s painful, and even after taking a toothbrush to my bruised hands when the project was done, it took days to scrub off all the grease. I’d always heard people complain about rear-suspension work, but having swapped out many of the components before—spring, sway bar, shocks, and more—I failed to enter this project with the appropriate degree of trepidation. Simply put, I hadn’t pulled the trailing arms before.
Tearing down the rear in Scarlett took almost six hours—three of them spent getting to the trailing arms, and another three spent getting them out. With the mix of disintegrating bushings, rusted-together alignment shims, and parts that appeared to have been assembled on the frame prior to the body drop, only one of the cross bolts could be removed; the driver-side arm had to be cut out of the car. So consider yourself warned: There’s a reason mechanics charge—and get—a lot of money for this job. And depending upon your financial position, mechanical inclination, and pain tolerance, it may very well be worth it to pay someone else. Personally, I’d still rather do it myself.
Now on to what we’re doing and why. The purpose of an independent rear suspension is to keep the tire perpendicular to the road, even while the car rolls toward the outside of a curve. This is done by causing the tire to gain negative camber—or lean inwards at the top—as the suspension compresses, which compensates for the car’s outward roll, keeping the tire relatively square to the roadway. In the shark suspension (as in the midyear before it), there are three links that control the angle of the wheel: the axle halfshaft, the camber rod beneath it, and the trailing arm.
The axle halfshaft floats in and out, which causes undesirable slack in the suspension. Unfortunately, that’s an inherent part of the design and can’t be changed without surgery well beyond what we’re doing here. The other two links, however, can be improved. The factory camber rods, which are usually adjusted by means of an eccentric locking system, have already been replaced on Scarlett with a pair of easily adjusted camber rods from Vette Brakes. The trailing arms, meanwhile, will be replaced with a coilover conversion from Van Steel, which accomplishes several different things.
Available from Muskegon Brakes, the Van Steel conversion comes with a new pair of trailing arms, as well the coilovers and adjustment tools. Coilovers are shocks with coil springs that encircle the shock tube and are mounted directly to it, usually with a spring perch that mounts on threads on the body of the shock. By connecting the two, the shock can more effectively dampen the action of the spring. And since it’s all a single unit, it’s easier to install and easier to adjust for ride height.
Another advantage on the C2/C3 platform is that the kit does away with the factory transverse leaf spring. The spring ties the two wheels together, which effectively reduces some of the independence between them, and with wider wheels such as the 17x9-inchers we’re using, the ends of the spring interfere with fitment. When we originally put the wheels on, we had to jack up the height of the rear spring—and ride height with it—by about an inch to make the ends of the spring clear the tire sidewall. And the tire-clearance thing isn’t just academic: Having once had a rear spring bolt rip the sidewall out of a tire on my old ’71 big-block, I’m especially grateful for the added clearance offered by the coilovers.
The Van Steel conversion is available for both small- and big-block applications, and with single- or double-adjustable shocks. While Scarlett is currently powered by a 350, we’re building an LS motor that will produce enough power to justify the stiffer big-block springs, so that’s what we selected, along with the single-adjustable shocks.
Once the trailing arms were removed, we shipped them off to Van Steel for the bearings to be rebuilt and installed in the new trailing arms. (If you plan to do the bearing swap yourself, you can follow the directions included with the kit for this portion of the job.)
With the completed conversion in hand, there were a number of obvious improvements in the basic setup (in addition to the obvious ones such as the fresh bushings). First of all, the folded-sheetmetal construction of the factory arms was replaced with ¼-inch-thick steel, with welded reinforcement ribs on the inboard side of the arm. Additionally, the arms were contoured to allow clearance for wider tires, and the parking-brake bracket was relocated to the top of the arm, moving it away from the sidewall.
The arms came fully assembled with the rotor run-out checked and the rotor marked for correct reassembly, as well as with new parking-brake hardware installed. Frankly, the whole setup looked so good I was reluctant to put it underneath a car, especially one that I drive in the rain. But things are meant to be used.
For details on the teardown process, see the accompanying photos. In the next installment, we’ll install the new rear suspension, and see what kind of difference it makes.