Last month we tore down the rear suspension on “Scarlett,” our ’72 coupe project car, so we could install a Van Steel coilover conversion. At last count, we were six hours of labor into the project, having removed everything down to the trailing arms and then shipped those out to Van Steel to get the bearings rebuilt.
For some reason, I was under the impression this was the hard part. But while the teardown procedure was no doubt challenging, getting the new rear components in, bleeding the brakes, and then swapping out the front coil springs for lower-rate units tacked on 26 additional hours of labor, for a total of 32 since starting on the rear—not counting trips to the machine shop, parts store, and alignment rack.
The Van Steel trailing arms, which are built of heavy-duty ¼-inch steel, came with Bendix factory-style brake rotors installed, and the runout already checked. Since we’re running a Wilwood setup, we needed to swap out the rotors, which means checking the runout again to make sure they’re running true.
To do that, slip the rotor over the lugs and bolt it in place. Mount a dial indicator on the hub or trailing arm, then bring the indicator in contact with the rotor, set at zero, and rotate the rotor to make sure there’s no more than 0.005-inch difference in the reading. If there is, remove the rotor, realign it a couple of lugs over, and reinstall it. Tighten the lug nuts back down, and try again: If that doesn’t work, you’ll have to remove material from the rear of the rotor where it seats on the hub. (Since I didn’t have a dial indicator, I took the assemblies to North Georgia Machine, where a quick check showed the runout was well within spec.)
Once that’s done, mark the hub and rotor so you know how to index the latter for reassembly. You’ll want to remove it before installing the trailing arm to reduce the amount of weight you’re wrestling with.
Before installing the trailing arm, it’s a good idea to clean out the frame pocket and inspect the mounting and cotter-pin holes to make sure everything will go into place. On Scarlett, the inboard cotter-pin hole on the passenger side was only half there, and had to be drilled out. Now is also a good time to drill out the factory upper shock mount to 0.5-inch. Just make sure you don’t punch through into the fiberglass on the inboard side of the mount.
Next, slip the front of the trailing arm into the frame pocket and slide the cross bolt in to hold it in place. This is going to take a little jockeying around, so find a good way to support the weight, and get comfortable. Once the bolt slips into place, get the nut started and slide in the alignment shims. While you may be able to reuse the original bolts and shims, I ordered all new stainless parts.
When I took apart the factory setup, I carefully laid aside the shims so I could reinstall them in their original orientation. Unfortunately, they wouldn’t all fit, so I took the new ones and roughly centered the trailing arm until I could get the car aligned.
Now, bolt the halfshaft to the hub. Since I had a pair of Dragvette halfshaft loops on the car, I slipped those over the halfshafts before bolting them up. Be sure to keep the included French locks in place while installing the bolts. My assembly manual shows a range of 60-90 lb-ft for them; given their function, I went with 90.
The new setup should be pretty tight, so be aware it may take some wrestling to get the bolt holes lined up. You may find it helps to put the car in Neutral so you can rotate the halfshafts to align everything. Keep in mind that you’ll need to put it back in Park to torque down the bolts, so expect to spend a lot of time getting out from under the car, changing the gear, sliding back underneath, and so on.
Next, tap the camber-bar mounting bolt out of its seat, using a punch if necessary, so the outboard end of the bar can be installed; with that done, hammer it back into place. Again, this may take some wrestling and prying. Once I got the bolt through the camber bar, I slid the lower mount of the halfshaft loop into place on the mounting bolt before securing it with the nut; I also tightened down the upper mounting bracket for the safety loop at this time.
Now is also a good time to make sure your camber bars are tight. I used Vette Brakes and Products bars, which use a jam nut to keep the bar from unscrewing. They weren’t tight enough, which caused the bars to loosen as I drove the car to the alignment shop. The result? Dangerously excessive negative camber and one destroyed rear tire. Lesson learned.
Slip the upper shock-mount reinforcing bracket around the factory bracket, orienting it in the same direction as the factory mount (one toward the front, one to the rear), and weld it in place. If you can’t weld it during the initial install, don’t worry: It can be done later. Just be sure to remove the shock before you fire up the torch.
To mount the coilover, slip the top of the shock into the mount and bolt it in place, making sure to orient the adjustment knob at the bottom toward the inboard side. Our upper mounting bolts were a little long, so we used a bench grinder to shorten them. Verify that you’ve taken all the pressure off the spring before you start installing the coilover at the top. Once it’s in place, tighten the two jam nuts on the bottom of the coilover, mount the bottom of the shock, and bolt it into place. The nut should be toward the rear.
Other than adjusting spring tension and ride height, that’s it for the coilover-specific installation; the rest is similar to the factory reassembly procedure. Install the parking-brake cable, adjusting the parking-brake shoes if needed using the serrated wheel assembly at the bottom of the hub. (Check your Haynes manual for instructions.) Install the brake rotor, followed by the caliper, then connect the brake line, taking care to route it around the coilover. (You may need to use a flexible line.)
Next, I installed a 0.75-inch rear sway bar supplied by Addco. While small-block C3s didn’t generally come with rear bars, they should have the necessary threaded mounting holes. Unfortunately, someone had puttied in the rear holes on my car, so I got to dig the stuff out and chase the threads using a bolt before installing the sway-bar brackets. I also had to remove one of the exhaust hangers for clearance.
To connect the bar to the trailing arms, install a bracket on top of the arm and thread two bolts through it, into the bottom bracket (the one with two weld nuts installed in it). Unfortunately, the holes in the brackets and the ones in the arms were a little off, so I omitted the bottom bracket and used Grade 8 hardware (bolt-washer-arm-washer-lock-washer-nut) to bolt the top one directly to the arm. With that in place, assemble the link with its multiple bushings and washers, remembering to tighten it down once the car is back down on its tires.
One of the challenges of this particular assembly is that I had selected 9-inch-wide wheels from Summit Racing, and ordered them with an extra inch of backspacing. This left the inside sidewall of the tire either in contact with the rear sway bar, or frighteningly close to it. I’m no fan of wheel spacers, but there weren’t many other options, so I bought a set of 5⁄16-inch spacers at the local O’Reilly, then had 0.125-inch shaved off of them at North Georgia Machine. This setup provided enough inboard clearance, but didn’t push the wheel out so far that it prevented sufficient lug-nut engagement.
That done, it was time to bleed the brakes and check the ride height. Since the 550-pound front coil springs that were in the car raised the nose, I swapped them for a pair of 460s from Muskegon Brake. This gave me the lower stance I was looking for on both ends. The top of the rear fender arch now sits roughly 25 inches from the ground, with the front about a half-inch lower.
The next order of business was getting the car lined up using the alignment specs in the instructions. Van Steel provides three sets of specs—street, advanced street, and track—and I went with the advanced-street settings. After driving a bit to get acclimated to the car, you’ll also want to adjust the shock stiffness to meet your driving habits. Van Steel suggests starting with 5 or 6 clicks, which is halfway through the shock’s adjustment. Exceeding the maximum number will damage the shock, so be wary on the top end of adjustment.
I’ve now got about 700 miles on the new rear suspension, and while I have yet to flog the car in a controlled environment, it’s an entirely different animal on the road. There’s no longer a need to “set up” for a curve by taking the slack out of the rear suspension slowly before putting it under load. Turn-in is sharp and immediate, and the rear simply sticks, responding especially well to acceleration through—and out of—curves.
It sticks well enough, in fact, that it’s easy to feel how deficient the factory seats are when it comes to lateral support during hard cornering. I guess that explains the C5 sport seats sitting on my office floor.
Special thanks to Leon Arrowood and Rick Clough.
Check out the rest of the series in Part 1 and Part 2 of the Sure-Footed Shark!