First to go in were the front Tokico HP shocks ($350) and Granatelli Motor Sports (GMS) springs ($285). Tokico's HP line claims a noticeable performance improvement over most factory shocks, and a long performance life. The progressive-rate Granatelli sport springs are designed to lower the ride height by 1.25-inches, and it shows when compared to the factory front spring height (center). Notice that the GMS spring coils are wound progressively tighter from top to bottom. During normal driving, the broader-spaced coils provide a softer ride with a factory feel. When significantly compressed, such as during hard cornering and braking, the closely spaced coils contribute a more rigid spring response.
Jose of Muscle Cars USA took us through the standard procedure for removing the front shock and spring coilover assembly. He began by separating the brake master cylinder from the booster so it could be moved out of the way of the left upper control arm mounting hardware. He then removed the two upper control arm bolts and other six upper control arm fastening nuts, both left and right (arrows).
Next, he disconnected the sway bar from the lower control arms.
He then removed the bolts connecting the shocks from the lower control arms (arrows).
Jose opted to disconnect the upper control arms from the spindles rather than the lower control arms. The top of the shocks will need to be separated from the upper control arms--an operation more easily accomplished with the control arms removed from the vehicle. With the other connection points of the upper control arm previously disconnected, the upper control arms and shocks can be removed from the car as units and then separated on the bench.
The first step in installing the new shock and spring assembly is fitting the springs to the shocks. Spring removal and installation for a coilover assembly requires a spring compressor. Without one, it's impossible to get the new spring compressed enough to lock down onto the shock. Removing a coilover spring from a shock without a compressor will send the fastening nut, spring cover, and spring rocketing across the shop with lethal force. Use of the spring compressor requires care and attention; compress each side a few turns at a time. Misuse of this tool can prove to be a lesson in ballistics, resulting in broken fingers--or worse.
Our Tokicos required some twisting of the shock base mounts to get them properly aligned. The bolt holes in the lower shock mounts must be positioned vertically in-line with the shock. The force required was definitely a testament to the strength and rigidity of the Tokico bushings.
Installation is essentially the reverse of the removal. MCUSA recommends a light lubricant on all bushing and pressure-relative connections, such as the lower control arm/sway bar connections. Also, be sure to put a new cotter pin on the upper control arm castle nut (arrow) when reconnecting to the steering spindle. After bending the old ones around during removal, they're now much softer and more likely to break or shear.
The installed combo will contrast nicely against the OEC C6 wheels.
While the brake master cylinder was out of the way and the upper control arm fasteners disconnected, we moved to the installation of the front shock tower brace, which mounts directly to the control arm bolts and studs. The GMS shock tower brace ($178) is a pretty hefty component that will noticeably increase chassis rigidity on the slalom course and during hard cornering.
Longer control arm bolts are not necessary, but the brace did require a little finagling to get a good seat on the shock tower. We took a few minutes to elongate the mounting holes on the brace and the bar seated perfectly once the fasteners were tightened.
Next, we moved to the driveshaft tunnel to install the Granatelli g-load brace and driveshaft loop combo (top, $149). The driveshaft loop is a safety device; a bonus for us, though designed primarily for a higher-horsepower or racing applications. Of all the components we're installing, we're most impressed with this one in terms of quality for price. It looks and feels bulletproof. Made from heavy-gauge steel, it makes the factory brace (bottom) look like corrugated tinfoil and has less than half the thickness of the GMS unit. Installed, the new brace should increase central chassis torsional stiffness, particularly during hard acceleration.
Installation of the brace and loop is simple, and would probably take even the most sluggish shade tree mechanic 45 minutes or less using jack stands and box-end wrenches. Jose and Thom completed the task in about 20 minutes. After removing the factory brace, the loop passes over the driveshaft and exhaust. The exhaust may require a bit of a tug to get the loop over it.
Thom connected the loop to the brace using the supplied hardware.
After connecting the loop and brace, the assembly bolts directly to the chassis at the points used for the factory brace. As shown, we first tried the installation using the provided spacers to create a little distance between the loop and the top of the driveshaft tunnel. Unfortunately, this arrangement caused the loop to rub against the exhaust, so we removed the spacers. Without them, the loop appeared to make some contact with the tunnel, but did not cause significant vibration while driving.
If the spacers aren't used, the bolts for the original brace will mount the assembly to the chassis. Installed, the assembly looks robust against the rest of the factory driveline.
Rear control arms were the next order of business. Like the driveline brace, the GMS tubular control arm ($220), is burly in comparison to the stamped steel factory unit.
Before any of the rear suspension could be disassembled, the axle had to be lifted separately to relieve tension on the springs. The lower shock mounts could then be disconnected from the axle.
Next, the factory control arms were disconnected and removed from the axle and the chassis.
The high-friction control arm bushing mounting points should be greased. The GMS units are equipped with zerk fittings to make the job easier; the bolts should be greased as well. Jose used an all-purpose suspension lube for the installation.
To facilitate the shock and spring installation, we lowered the height of the car while maintaining spring tension and switched out an axle jack for jack stands. Then we disconnected the shocks from the shock towers, which are directly behind the rear seat bottom and concealed by sections of carpet. To get at the mounts, we cut out the carpet perforations and the holes provided just enough space to reach in with one hand. Jose used a ratcheting box-end wrench to remove the top shock nuts. Clamping the shafts of the old shocks is also necessary to keep them from spinning while removing the nuts. GM used a nylon thread locker on the top of the shock shaft that creates extra tension between the nut and the shaft.
After the shocks were disconnected from the towers, the lower shock mounts could be disconnected from the axle and the car could be raised off of the jack stands, thus releasing the spring tension. The shocks came out, once pulled past the factory shock tower grommets. With a little downward pressure to the axle, we removed the springs from the axle perches (along with the rubber upper spring insulators).
Though installation is the reverse of removal, care should be taken while reassembling the upper shock mounting hardware and bushings. Jose lubricated the upper shock-mount assembly with silicone spray to prevent vibration and then verified that the new springs were seated correctly.
Mounting alloy wheels can be difficult without scratching the wheel surface. MCUSA uses a special tire-mounting machine that grips the wheel by the outside edge rather than the inside edge (conventional). Plastic claw covers prevent marring chrome or painted wheel surfaces.
Jose torqued the wheels to recommended spec. The C-6R wheel ($1350 set) and Bridgestone ($880 set) combo looks hot on our black Z.