After taking Andrew Sivori's '99 C5 convertible about as far as the California Smog laws would allow, it was time to bend a few rules. This go-round we wanted to outfit the Vette's LS1 with a trick emissions-legal cam and a high-flowing exhaust system to enhance the already impressive performance managed from only a set of AFR cylinder heads, Flowmaster mufflers, BBK throttle body, cold air kit, and intake manifold. To help us put together a killer combination, a call was placed to A&A Corvette Performance in Oxnard, California. A&A has been responsible for building some of the fastest C5s and C6s in the nation in its 4,500-square-foot shop over the past five years. Though it's most known for its in-house built supercharger kits making 600 to 900 rear-wheel horsepower on a whim, A&A fit us in to its busy schedule to give this stock cube, naturally aspirated Vette some love.
Starting from the rear, the current mufflers were to be replaced by a Corsa Cat-Back with the randy PaceCar Edition mufflers and 2.5-inch mandrel-bent 304 stainless steel pipes. The Corsa mufflers feature a multi-chambered design that uses Reflective Sound Cancellation Technology, which helps produce a high-pitched, Ferrari-like exhaust note at WOT without any low-rpm droning. The Corsa Cat-Back came highly recommended from Kooks Custom Headers, whom we had commissioned to build a set of 1.75-inch long tubes. Using a 3-inch velocity spike collector, the race headers would provide optimal flow and backpressure for the heads and stock cube motor. An X-pipe with high-flow cats was obtained from Kooks as well to mate the headers and Corsa Cat-Back. Meanwhile, A&A Proprietor Andy Green gave COMP Cams a call to have it send out a custom grind cam to help pass the sniffer, combining an LSK intake and XE-R exhaust lobe. To compensate for the squeaky clean emissions, a peculiar split (much like a cheater cam) was used to take advantage of the high-flowing heads and exhaust. Believe it or not, the cam card read .637/.571-inch lift, 223/228 duration at .050 and a 114 LSA.
In an effort to dial-in the best possible combination for the application, the 205cc heads were traded for A&A's small heads of choice-A&A/West Coast Racing Cylinder Heads 215cc CNC-ported Edelbrock LS1s. West Coast developed the CNC program for A&A using Edelbrock's Pro-Port casting, as it is the perfect candidate for building even some of the most potent street-going applications. The substantial wall thickness allows virtually unlimited runner size and shape that West Coast found ideal for not only its 215cc program for stock cube LS1/LS2s, but also a 245cc head for big cube strokers and forced induction. Anything beyond these limits, West Coast says, calls for one of its newly developed CNC-ported L92, LS7, or All-Pro heads. Thankfully the cathedral port, stock geometry Edelbrock heads would match up well to the stock rockers, valve covers, and BBK intake while still enabling up to 311 cfm. However, just to be sure, we had BBK send out another intake to West Coast to have it port-matched and polished. At the very least, this should help free up a few more ponies by getting rid of some of the rough as-cast finish on the intake runners.