March 2005 � Big Mouth Air Dam & SLP cold air intake
These are both subtle but worthwhile modifications to compensate for some of GM�s design deficiencies. Road testing showed the Big Mouth doubles the airflow through the radiator. The headless rabbit can vouch for it. The stock intake is also flawed, as it draws air from the a/c condenser surface, and from under the hood. The SLP kit puts the intake directly in the path of air flow. It increased highway mileage by 2-3 mpg, so I know it works.
May 2005 - Cooling fan overrides
It�s frustrating to bracket race when you have no control over the engine temperature. The stock fans come on at 228 degrees, which is fine for cooking eggs. I used a double-throw switch to send a ground signal to both cooling fan relays. With the flip of a switch, I can force both fans on. This drops the coolant down from 225* to the 185* thermostat temperature in about 2 minutes. There�s lots of schmucks at the track pushing their cars up the staging lanes trying to keep cool. Maybe that�s why they buy imports, nobody wants to push a Chevelle. My best run with this setup was 9.09@78mph
July 2005 � 4 3 Rebuild
Don�t drag race without clutch fluid. I did because I was too lazy to replace the leaking clutch hydraulics. I wore out my synchros and chewed up several of the gears. It began popping out of 3rd gear on deceleration. I began to rebuild it with a new clustergear, 1st gear, 3rd gear, forks, synchros, and an empty wallet. I also got a new clutch and hydraulics. Then I decided to stick all of it on the shelf and buy an entirely different transmission, and every part that touches it.
September 2005 � Ujoints and Bearings
The factory Spicer u-joints were good for about 75,000 miles. They are not greasable and were just beginning to run dry and chew up the needles. I replaced them with forged Spicer joints. I would recommend the greaseable u-joints for non-racers. What they lack in ultimate strength, they'll make up for in longevity. Either way, don�t go cheap on these, especially if you drive your car like God intended. The same applies for the wheel bearings. The factory bearings are made by NDH, and were originally designed for family sedans before the C4 was born. They are already far too weak to handle the G-forces the Corvette is capable of, and the foreign made bearings are much worse. I used up a set of Chinese bearings in one day of autocross. That�s 60 seconds of hard driving.
September 2005 - Bushings
The 20 year old rubber bushings were also shot. The upper control arm bushings had fused to the shafts, and the lower shock bushings had deteriorated from oil.
I used a kit from Energy Suspension, which doesn't include the sway bar and shock bushings. Some of their bushings were too wide, and when tightening the bolts, it would squash the bushing before ever clamping down on the inner sleeve. This will cause binding, and can be fixed by either narrowing the bushing shoulders, getting longer sleeves, or narrowing the hole on the suspension part.
The upper control arms go together a specific way. I bought a hydraulic press from Harbor Freight for $150 to tackle this job, although a bench vise and sockets will be enough for most of them.
November 2005 � 6-speed conversion
I purchased a german ZF 6-speed out of a 1991 Corvette. ZF stands for Zahnradfabrik Friedrichshafen, which rhymes with, uh... Well, it is bulletproof, and noisy as hell. GM used this �black tag� version in Corvettes from 89-93. There was no other transmission available that could handle the torque and had enough gear spread for the Corvette�s top speeds over 170 mph.
This is an involved swap, but basically requires changing the bellhousing, clutch set, trans, driveshaft, clutch hydraulics, and modifying the fiberglass tunnel in the car. With the stock 3.07 rear end, and a tall 0.50 overdrive gear, I was taching 2000rpm at 100mph in sixth gear, and getting 28mpg at 85mph. I also ran a new best of 8.91@81 from just the trans swap. Amazing!. I'm going to need some shorter gears...
While I had the interior torn apart, I used a wannabe Dynamat called �Fat Mat�. I wouldn�t recommend it. The ZF6 is a noisy transmission when used with a standard flywheel, so the goal was to keep the car quieter inside. If you want to drown out gear noise, you'll need something less dense to absorb it. Supposedly this FatMat is just industrial "Peel n Seal" with a fancier price tag.
Autocrossing is the most abusive thing you can do to your car�s suspension. I�ve only done 3 autocrosses, and have already gone through 7 wheel bearings and 3 balljoints. I replaced the balljoints with Moog, and the bearings with SKF/Chicago Rawhide and NDH. It seems the only way to get long life out of a Corvette wheel bearing, is to buy a quality one, and give it several thousand break-in miles before abusing it.
February 2006 � Raptor Shift Light
The 84-89 Corvettes used a digital tachometer. It�s pretty, and pretty worthless at the race track, because the LCDs can�t keep up in 1st gear. So I installed a shift light in the dash vent. It shines extremely bright, and doesn�t clutter up the interior. This mod is absolutely necessary for consistency in bracket racing.