Pursuing Performance

As a trial experiment, we pulled the lid off of the filter box and faced it forward so it became the inlet to the intake tract. We stuck the stock paper filter element in it and made a pull, showing an instant gain of another 3 hp, and this was with the resonance baffle still in place. We were onto something.

We started scheming to create a high-flow air intake setup, with visions of drilled filter boxes and 3-inch exhaust tubing dancing in our heads. Of course, we also wanted to use a high-flow aftermarket filter, and that's when we learned that K&N actually offers a complete cold-air kit for the Caprice. Actually, this FIPK (Fuel Injection Performance Kit) was developed for the Impala SS, but the hardware is identical on the cop-spec Caprice, so we ordered it up. This kit includes a new filter box, which seals to the hood to keep out hot engine-bay air. It also uses a conical filter rather than the stock panel-type, and it even includes a tube to replace the resonance baffle.

Installation is relatively simple. The stock filter box is removed, which is a simple matter of a couple screws and a few snap-fit connections at the base. The K&N box then attaches to the same mounting points and includes a separate filter for the hose that feeds the engine's air injection pump, which was originally attached to the stock airbox...

...The filter and tube attach to the box, and the tube is then connected to the stock MAF. When it was all said and done, the K&N kit boosted power to 235 hp and 290 lb-ft of torque.

After the dyno test was over, we realized there was another simple trick up our sleeves for the Caprice that should have been tested. The throttle body used on LT1s (like the Tuned-Port engines before them) has a small passage inside for coolant, which is fed via a small hose that taps into the cooling system. The purpose of this arrangement is to prevent ice from accumulating on the throttle blades during cold-climate startups, but the rest of the time it just adds heat to the incoming air. By simply bypassing the coolant connections on the throttle body (connect hose A to hose B), the heat is eliminated--a change reputed to be worth around 3-5 hp in many cases. We'll try this out next time we hit the rollers.