Tuning the Forgotten EFI System

When I was growing up, my mother taught me that if I didn't have something nice to say, I should say nothing at all. As I grew to adulthood, this made me an eternal optimist, believing that something good can be found in every situation. Keeping this mindset and ignoring the naysayers, I have discovered that, when adjusted properly, the Cross-Fire EFI system can deliver excellent driveability.

We all know that there’s no such thing as a bad Corvette, but if love and commitment are measured by loyalty, the General certainly put Corvette purists’ devotion to the test with the 1982 and 1984 model years. Facing new competition from the Land of the Rising Sun (the Toyota Supra and Datsun 300 ZX Turbo), this is the rabbit they pulled out of their collective engineering hat--a wet-flow fuel-injection system with an intake manifold that offers an entry angle and port match to the cylinder head so poor that it wasn’t really worthy of a Corvette.

But these cars are out there, largely ignored by the motoring press, including us at Corvette Fever. Knowing that the owners of Cross-Fires are as rabid as any other Corvette enthusiasts, we’re anxious to make up for past transgressions, and have been collecting the most comprehensive Cross-Fire information to share with you. We started with Moses Ludel’s fundamentals story in the Dec. 1999 issue and continue here. Robb Northrup has been hard at work, and there’s more to come.

Mission Possible

This design had a few Achilles’ heels: vacuum leaks at the plenum-to-intake gasket, worn throttle-body bushings, and out-of-balance throttle bodies. Our subject car, a 1982 with a small aftermarket cam and the complete factory fuel system still intact, suffered from a maladjusted EFI system.

The purpose of the balance setting is to synchronize both throttle bodies by having the throttle plates at the same opening angle. This can be accomplished after some maintenance procedures are performed. The throttle angle is determined by reading the venturi vacuum signal, which is very weak, but accurately tied to the throttle opening. This will require the use of an inches-of-water gauge, or manometer. They're available from most professional tool distributors. As we present the procedure to balance the EFI system, it may at first seem complex and confusing. But read it through a few times before trying to accomplish the task.

For this, Corvette Fever visited Owen's Auto Service in Trenton, New Jersey, where we worked with technician Bill Doran, who is the owner of our subject vehicle. Both Owen and Bill are Corvette aficionados and have worked extensively with all years of Corvettes, including the Cross-Fire system. If you feel that there is a little too much to this procedure or the investment in tools is too great for a one-time adjustment, the crew at Owen's will perform the complete setup for $275.