Driveline Modifications

1.6:1 Ratio Roller Rockers To further enhance the volumetric efficiency of my L99/265ci engine, I've installed the GM performance version of the Crane manufatured LT4 (Corvette) 1.6 roller rockers. Using the 1.6:1 ratio rockers over the 1.5s doesn't increase the duration or change the timing of the valvetrain, but they do allow the valves to open faster and further. This increased lift and faster opening of the valves allow for a more complete filling of the cylinders and improved scavenging on the exhaust stroke.

Throttle Body Heater By-Pass Engine coolant is circulated thru the throttle body to reduce freezing during cold weather operation, yet this process also heats the incoming air. The by-passing of the coolant to the throttle body helps to keep the incoming air as cool as possible. Because the cooler air contains more oxygen per volume than the heated air, it then becomes possible to produce more horsepower without increasing the air flow.

Corvette Engine Dress After removing the large air intake baffle that covers the top of the engine, the Corvette injector covers worked nicely to dress up the engine by hiding the newly exposed injectors, and the unsightly engine harness.

Air Intake System Originally the engine came with two baffles in the air intake system, both of these were removed to allow for a smoother flow of air to the engine.

After removing both baffles from the system, I made this pipe to connect the air box to the Intake elbow. The elbow is from a 4th generation F-Body with the 1LE option code. The connecting pipe is made from two (3 inch 45 deg.) PVC elbows. These elbows can be found at any local hardware store then painted any color you choose. I painted mine with OEM trim color black.

Ported Air Box The original air box was retained, but was ported to help promote better airflow. On the inner fender side of the air box I drilled three 1-3/4" holes along the side, then from the inside I drilled a 5/8" hole centered in each square of the waffle style pattern on the floor of the air box. Although this modification did improve airflow which increased top end performance, it also increased the noise level at WOT (wide open thottle).

K&N Air Filter To take full advantage of the improved air intake system I also replaced the restrictive factory disposable paper air filter with the far superior K&N performance filter.

HEADERS Tri-Y Headers

Exhaust The single exhaust system was removed to make way for a less restrictive dual exhaust. The new system is 2-1/2" aluminized pipe custom bent to the same form as the Impala SS exhaust. Standard aftermarket "turbo" mufflers are used to silence the rumble to a mellow note. This system is noticeably louder than the Impala's OEM exhaust system, yet subtle enough to be enjoyed on long road trips.