Next up, we had to buck up and spend some coin on what we consider the first of the more substantial modifications. With the minor bolt-ons behind us, it was time to free up the intake tract with a larger throttle body. We elected to use Edelbrock's twin 52mm assembly (PN 3809) to replace the original 48mm double-barrel unit. Aside from offering greater airflow from larger-diameter bores, the Edelbrock piece also enhances total airflow by incorporating a smoother transition from the ovoid opening into the two individual throttle bores. Also, Edelbrock includes a new TPS (throttle position sensor) with its throttle body to save time and hassles. For those with more serious applications, Edelbrock also offers a larger 58mm unit, but this would be overkill for our project.
When installing a throttle body onto any twin-bore TPI or LT1/LT4 engine, keep in mind that engine coolant is designed to pass through it to prevent the throttle blades from icing during cold starts. When removing and installing the coolant manifold bolted to the underside, keep in mind that you'll be opening up the cooling system and a quart or so will leak out.
With the new Edelbrock throttle body installed, Chris Winter's Dynojet was able to measure a very sizable gain of 8.1 horsepower and 23.1 lb-ft at the wheels at peak output. But the real kicker was how much torque and power it picked up down low, which shows how a smoother air inlet transition at the throttle body can greatly help low-rpm performance. For instance, at just 3,300 rpm our engine was making 7.6 more rear wheel horsepower and 12.0 more lb-ft of torque. This was backed up with another run on the dyno, and conclusively, we were impressed. Now our tally was up to 261.3 rear wheel horsepower at 5,600 rpm and 353.2 rear wheel torque at 2,900 rpm.
At the track, we were able to drop our times to 14.405 at 92.81 mph for a reduction of just over a tenth (0.115 seconds) and a slight bump in trap speed of 0.26 mph. Our weather situation didn't help things on the track since the heat sent our thermometers north of 90 degrees Fahrenheit. This made our runs all the more impressive. Our dyno figures were all corrected to SAE standards, while our track times were left raw.
Making Headway-Sort of
With the engine freed up of some extra power through simple bolt-ons, our next move was replacing the exhaust headers. We've seen a few offerings on the market, but were never too satisfied with the quality or fit of the products. Rather than risk it with a header of questionable lineage, we elected to use Edelbrock's quality TES (tubular exhaust system) shorty-style headers for more power and, of course, less weight. They replace the factory cast-iron manifolds and meet 50 state emissions requirements since the catalytic converters are retained in the factory locations and the AIR (Air Intake Recirculation) system is left untouched. Available in a ceramic-coated or Ti-Tech finish for a bit less moolah, we chose to go with the latter to stay in line with our budget buildup.
With our Killer Whale on the lift at Crazy Horse Racing, proprietor Chris Winter once again helped install the parts. Removing the factory manifolds was an easy task, necessitating the removal of just a few pipe fittings for the EGR tube on the passenger side and the two aforementioned AIR injection pipes on the topside. It's easiest to remove everything underneath, so a vehicle lift is strongly recommended when performing this upgrade.