1972 Chevy Corvette - The Sure-Footed Shark, Part 3

Part 3: Installing Rear Coilovers on our 1972 Project Car

Jeremy D. Clough Dec 17, 2013 0 Comment(s)
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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.

Brake Rotor 2/28

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.

Factory Hardware 3/28

01 While you can reuse the factory hardware, it seems a shame to reinstall all those rusty parts. I ordered a kit that had all the bolts, cotter pins, and alignment shims in stainless steel.

Drill Upper 4/28

02 Before you start installing things, it’s a good idea to drill out the upper shock mounts to 0.5-inch. Go slow and don’t punch through to the fiberglass behind the mount.

Coilover 5/28

03 The spring on the coilover is held in place at the bottom by the two jam nuts, which can be adjusted to change tension and height. The knob at the bottom is used to adjust the stiffness of the shock.

Trailing Arm 6/28

04 After cleaning the frame pockets and holes, insert the front of the trailing arm into the pocket and slip the cross bolt through it from inboard outward. Long needle-nose pliers may help, as the bolt otherwise tends to be hard to control.

Lower Cotter Pin 7/28

05 A cautionary tale: The lower cotter-pin hole on the driver-side frame pocket wasn’t clear, and had to be drilled out. Better to know that before you start assembling things.

Castle 8/28

06 Get the castle nut started on the cross bolt. Later, it will need to be torqued down and secured with a cotter pin.

Alignment 9/28

07 Insert the alignment shims, slipping the open end over the cross bolt, then rotating them down to the bottom of the frame pocket. While I tried to replicate the shim thickness prior to installation, it didn’t work, so I simply centered the trailing arm until I could get the car aligned.

Long Cotter 10/28

08 Once the shims are in place, install the long cotter pin through the bottom of the frame pocket from the outboard inwards, then spread it open to hold it in place. The pin isn’t bent: That’s the reflection off the trailing arms. They’re that shiny.

Castle Nut Cross 11/28

09 Torque down the castle nut on the cross bolt and install the cotter pin through the hole, bending it to hold it in place.

Halfshafts Bolts French 12/28

10 Now bolt up the halfshafts, making sure to torque the four bolts down to the appropriate value. The thin piece of metal between the hub and the flange is a French lock, which should be bent down to hold the nuts in place once everything’s installed.

Camber Bar Mounting 13/28

11 Tap out the camber-bar mounting bolt so the outboard side of the bar can be mounted in its bracket. You may find that you need a punch to back it out far enough through the bracket to install the camber rod.

Camber Rod 14/28

12 This photo shows the camber rod mounted in its bracket.

Halfshaft Loop 15/28

13 Here, we’re bolting the bottom mount of the halfshaft loop into place on the mounting bolt for the camber bar. The top mount clamps into place on top of the trailing arm.

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.

Upper Shock Mount Reinforcing 16/28

14 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.

Long Upper Shock Mounting 17/28

15 The upper shock-mounting bolts come a little long, and may need to be shortened to fit. While one was fine the way it was, I had to hit the other with the bench grinder.

Bolted 18/28

16 Here’s the upper shock mount with the reinforcing bracket and coilover bolted into place. Next, install the bottom of the shock in its mount.

Parking Brake 19/28

17 Slip the parking-brake cable into place on top of the trailing arm and connect it. (You may have to spread the bracket a little by prying it.) Once in place, slip the Mickey Mouse clip over it to secure it.

Parking Brake Cable Adjust Serrated 20/28

18 Snap the end of the parking-brake cable into place and adjust the parking brake using the serrated wheel on the bottom of the hub.

Brake Caliper 21/28

19 Install the brake caliper, being careful to route the line around the coilover. While the Wilwood calipers on Scarlett already had flexible braided-steel lines, you may need to add them if you’ve got hard lines.

Sway Bar 22/28

20 The first step in installing the sway bar is to snake it over the spare-tire carrier. Once it’s in place, snap the included bushings over either end. Note that the exhaust hanger has been loosened to clear the bar.

Bracket Frame 23/28

21 Screw the bracket into place on the frame, using the factory mounting holes. While the front bolt can easily be reached with a ratchet, there’s little clearance for the rear one, where a ratcheting wrench can help.

Bracket Trailing 24/28

22 This is the bracket arrangement that mounts on the trailing arm, and to which the rear bar will be linked. The longer bracket goes on top, with the hole extending toward the rear, and the bottom weld-nut bracket goes underneath the arm. I couldn’t get the holes to line up properly with the arm, so I didn’t use the lower bracket.

Grade 8 25/28

23 Using Grade 8 hardware, I inserted a bolt with a washer from underneath, then put a washer, lock washer, and nut in place to hold the upper bracket to the trailing arm. This configuration isn’t necessarily superior to the factory setup; it’s just what I had to do to make everything fit.

Link Assembly 26/28

24 Here’s the link assembly. Note the bushings above and below the bar, and the mount on the trailing arm. While you can install it with the car on a lift or jackstands, make sure you tighten it with the vehicle at ride height.

Fully Assembled 27/28

25 This photo shows the bar fully assembled, with one bracket mounted to the frame, and the other to the trailing arms.

Driveshaft Loop Coilover 28/28

26 This is the completed driver’s side, shown from the rear. From this angle you can see both the driveshaft loop and the threaded, silver body of the coilover.


Check out the rest of the series in Part 1 and Part 2 of the Sure-Footed Shark!

Sources

Summit Racing
Akron, OH
800-230-3030
SummitRacing.com
ADDCO Manufacturing
Linville, NC 28646
800-621-8916
www.addco.net
Van Steel
Clearwater, FL 33762
800-418-5397
http://www.vansteel.com
Muskegon Brake
Muskegon, MI 49444
www.muskegonbrake.com
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