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Building the Tom Henry RS
Part 4: Suspension Mods, Tires, Wheels, Headers and other Cool Stuff.
By: Hib Halverson
At the end of Part Three, we changed the valvetrain of the 3.8-liter V6 in the Tom Henry RS. We installed new, Yella Terra "Ultralite" 1.8:1, aluminum roller rocker arms, Katech valve springs and Katech titanium retainers on our 3800 Series II V6.
Ultralites are nearly 25% lighter than the stock 1.6 rockers and 8% lighter than the SLP aluminum rockers we took off. What's even better about the new Yella Terra rockers is from where in the rocker the weight was removed. It was mainly taken from the valve end where mass reduction would have more impact. The Katech springs (PN PSI-LS1511) have a little more pressure than the Comp springs in the motor previously and the Katech "ti" retainers (PN KAT-4678) are a little lighter than the Comp retainers we took off.
Less valve train mass and a little more spring pressure was the remedy for a valve float problem we experienced when running the engine over 5800 rpm. Before we went back to the dyno to validate that theory, we wanted to get some drive time on the new parts. We, also, wanted to have some headers made for the car. Finally, we wanted to perform some more suspension mods and add a few "safety" features.
A goal of this project was to have a 250-hp engine and pass an exhaust emissions test–not just any old "sniffer" test, either. It had to be the stringent "Enhanced Smog Check" required in the State of California's urban areas. Similar tests may be required in a few other states. We took the Camaro to Quality Auto Service in Pomona, California to see if the engine would pass with the modifications to date. Owner, Mike Garibay, is well-versed in emissions testing and service work. His shop is one of our favorite general repair facilities because of its good customer service.
The Enhanced test combines inspection of emissions parts with an exhaust gas test taken while the car runs on a moderately-loaded chassis dyno at both 15 and 25 mph. We easily passed the test. In fact, Garibay commented that he didn't see very many mod'ed cars that ran so clean.
Suspension, Wheels, Tires
The Tom Henry RS's rear suspension felt, well... "sloppy" is the best way we can describe it, in accel/decel transitions, during quick shifts at wide-open-throttle or on roads were slab joints or tar strips get the suspension hopping. This is caused by the soft rubber mount GM stuck on the end of the rear axle torque beam along with the weak-suck, stamped-steel beam flexing under load. Another problem? During hard acceleration, drive torque acts on the beam's length to decrease rear tire loading. This reduces traction, both in a straight line and accelerating out of corners. Lastly, when you lower a 3rd or 4th Gen Camaro, traction degrades even more due to decreased anti-squat caused by the change in rear suspension geometry.
Popular with autocrossers, road racers and drag racers is Global West Suspension's "TracLink" assembly (PN TSC-23). It alters rear geometry such that its leverage point moves to a more optimum location. Drive-torque-induced tire loading changes from negative to positive improving traction during acceleration, both straight line and out of turns. What's more, TracLink eliminates wheel hop and has a pinion angle adjustment. Finally, of interest to drag racers required to add a driveshaft loop, the mounting points for that are built into the TracLink.
Global West markets this product mainly for V8 cars, but the kit for a 3rd Gen V8/automatic Camaro, also, fits a 4th Gen V6. The installation requires removal of the left rear seat cushion, drilling some holes in the left rear seat well and one hole in the transmission mount crossmember. Other than that, TracLink is a bolt-on for all 4th Gens.
Like some racing-derived performance enhancements, this one has compromises for road cars. When it comes to noise, TracLink is not for the faint-hearted because, since it dispenses with the large rubber isolator at the front end of the torque beam, powertrain noise and vibration in the interior increases. We totally want the Global West TracLink's positive affect on acceleration and handing, so we'll take the noise, however, those expecting Camaros with modified suspensions to have interior noise-and-vibes levels the same as or close to stock should carefully consider this product.
The TracLink installation was done by Global West's technicians at its factory in San Bernardino, California and included the addition of "Rear Anti-Squat Brackets" (PN VTC-27). These brackets must be welded to the rear axle housing. Once in place, they compliment the TracLink by further improving traction exiting turns. Additionally, they are ideal for a lowered car because they further alter rear suspension geometry such that its instantaneous center moves to a point more appropriate when ride height is reduced. That change increases the rear suspension's percentage of anti-squat such that that car tends to hook better during hard acceleration.
Lastly, these brackets have two positions for the rear control arm pivots allowing drag racers to adjust the car's bite for track conditions or changes in ride height. With the TracLink and Anti-Squat Bracket installations complete, we bid all the good people at Global West farewell and headed back to our shop.
We wanted more radical tires and wheels, so we swapped the 245/50ZR16 Goodyear Eagle F1 GS-D3s on stock, 8" wheels we'd been using up to now for a set of 265/40ZR17 Eagle F1 Supercars on 9.5" Fikse Profil 5Ses. We should add that the F1 GS-D3s were on the car for several years providing good dry and wet traction and outstanding tread life on a car that gets driven pretty hard
The Fikse (it's "fick-sea" not "fis-ski", by the way) Profils are awesome-looking wheels. Because Fikses are so light for a street wheel, we could go from a 16x8 to a 17x9.5 yet not increase unsprung weight, but we expected this, considering their racing pedigree–cars on Fikses have won both the World's preeminent endurance races, the 24 Hours of Daytona (4 times!) and the 24 Hours of LeMans.
The Fikse Profil 5S is a modular design with a rotary-forged, CNC-machined, clear powder-coated, aluminum center. The rims are forged, heat-treated aluminum. "TechniPolish" is Fikse‘s standard finish and features a robust, liquid-cured clearcoat on the diamond-turned center section. The mirror-polished rims are left polished and uncoated to allow for touch-ups as needed in case of minor scrapes.
While brothers Matt and Jim Fikse (yep, it's a family operation with their name on the building) couldn't share specific manufacturing secrets with us, they did reveal that, unlike most wheel companies, Fikse USA manufactures its own centers and rim halves. Having done that since 1992, makes Fikse one of the few companies in the U.S. that controls the wheel-making process from start to finish. Doing that enables it to maintain a high level of quality few manufacturers can equal and none exceed. Fikse builds 4th Gen. Camaro wheels in two offsets, 38mm and 51mm. We chose the 38s because they slightly widen the car's track for a better look.
Needless to say, Fikses are not cheap, so wheel locks are manditory to deter theft. Initially, we reused the stock Camaro wheel locks but they didn't look very good. The Profils come with high-quality, McGard wheel nuts so we went looking for a set of McGard's locks, figuring they'd better match the nuts' appearance.
McGard makes perhaps the best wheel lock in the industry. They're made of hardened steel...not just "case-hardened," but hardened throughout and tempered. Like most locks, they require a special "key tool" and the design of the key and the pattern in the lock allow a virtually unlimited number of computer-generated combinations.
To install or remove the lock, the key's collar, aligns the key to the lock. All you need to is gently push the key over the lock then turn the key until the patterns engage. McGard locks are nickel-chrome plated. Basically, these locks will probably outlast the car. The simple function, outstanding security and excellent durability of the McGard design might be why they're OE on some 30 car lines, worldwide.
Jumping from the F1 GS-D3 to Goodyear's ultimate, dry traction tire, the wider, more grippy, F1 Supercar; improved straight line bite, cornering power and steering response. The Supercar, in 265/40ZR17, was originally developed for the C5 Corvette Z06 and is one of only a few tires which bridges the gap between all-round, ultraperformance tires, such as the "D3", and DOT-approved, radial road race tires which are not acceptable for general street use because of short tread life and almost nonexistent, wet traction. While the F1 Supercar is more sticky than what we took off, admittedly it's not the drag race tire that a "drag radial" from Goodrich, Nitto or Goodyear might be. Perhaps we'll try one of them in the future.
The main advantages to the Tom Henry RS with the F1 Supercars are improved at-limit handling due to more traction coming from a wider tread, more aggressive rubber compound and a tread block design skewed towards handling. Additionally, the F1 Supercar casing is designed to improve steering feel and response.
Where the Supercar gives-up a little to the F1 GS-D3 is in 1) wet traction--the D3's tread design is superior when it comes to channeling water away from the contact patch 2) tread life--because the Supercar has softer rubber and more shallow grooves--and 3) noise and harshness.
We hauled the Fikses and Goodyears over to Covina, California's Tucker Tire Service Co, where they were mounted and balanced. On return to our shop, we stuck the THRS up on jacks and swapped the tires and wheels then torqued the McGard nuts and locks. Man...those Fikses and F1 Supercars are just so damn pretty!
