Why Does the Cross-Fire Injection System Get Such a Bad Rap?

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1982 Corvette Collector's Edition

Though widely disliked, even by numbers-matching purists, this early EFI isn’t half bad.

Remember the bad old days when smog, safety, and fuel economy regulations ganged up and ruined automotive performance and style? For the first time since before the Ford Model T, cars actually got worse instead of better. Things were so bad that full-sized vans customized like rumpus rooms on wheels were the hottest enthusiast vehicles around, and we all just sat in the back crying in our beers about the performance we’d lost.

How bad did things get for the Corvette? In 1980 there was no manual transmission in California; just a slushbox and a 305-cubic-inch motor with 180 horsepower. In 1981 the 350-cubic-inch motor only made 190 horsepower, fueled by a computer-augmented Quadrajet carburetor. The hot, new C4 was already in the works, and with its sleeker hood-line, the carburetor and its big round air cleaner were not going to fit. Plus Chevy desperately needed a way to increase performance and federally mandated fuel economy. The Cross-Fire Injection System seemed to be the answer. The Cross-Fire managed to do all that was needed: fit under the hood, and save Chevrolet from a fiasco of warranty returns and lost luster to its shining halo car. So why does it get so much hate, even from Corvette lovers?

corvette cross-fire injection diagram

The simple answer is that people hate what they don’t understand, and in 1982 almost nobody understood fuel injection or computers. Cross-Fire was different, and it looked complicated. In reality, though, it was actually pretty simple with just a handful of sensors and a computer as complicated as a pocket calculator. As long as the mechanical adjustments were done correctly to synchronize the throttle bodies, it ran great.

The system monitored coolant temperature, throttle position, manifold vacuum, and RPM. Then it used an oxygen sensor to fine-tune fuel delivery. The two simple throttle body fuel injectors could fire up to 80 times a second, and the electric fuel pump could vary pressure from 9 psi up to 13 psi, when load, throttle position, or RPM demanded it. People in the know claim that between the size of the throttle body openings and injectors, this system can flow as much as a 750-cfm, four-barrel carburetor.

High performance cross-fire injection

The “cross” part of the name came from the design of the intake manifold, which was also the key to getting proper breathing while maintaining a low hood. The Cross-Fire manifold was very much like the old cross-ram, dual quad manifold which was a “factory” option back in 1967 for the Camaro Z28 race car in SCCA Trans-Am. Instead of an eight-legged spider of intake runners with a centrally mounted carburetor, the four runners from each side went straight across from the intake ports nearly to the valve cover, with a carb (or throttle body in the case of the Cross-Fire) mounted on each side. In racing, this let the little 302 breathe all the way up to 7,000 rpm and make 500 horsepower.

Original Z28 Cross Ram Manifold

The Cross-Fire Injection manifold, however, was a much lower performance version of the same design. The injectors could deliver the fuel. The throttle bodies could flow the air. Compression was up and a more aggressive cam was installed from the factory. Even choked with catalytic converters, the exhaust flowed respectably thanks to header-like manifolds. The problem was that GM shrank the size of the intake runners down to just 2/3rds of the size of the intake ports. They did this for better fuel economy, and to increase the flow velocity for better driveability. After all, this was their halo car and they needed it to run right without complaints from day one.

Inside of cross-fire manifold

Still, there are die-hard fans of the last of the C3 Corvettes here on Corvette Forum who like the system, and have no complaints. There are even several members with more than a quarter-million miles racked up on 1982 or 1984 (there are no 1983 Corvettes) Cross-Fire equipped Corvettes. Corvette Forum member toobroketoretire says “I have owned an ’82 for 23 years, and now have 275,000 miles on it. So I have a great deal of knowledge about the Cross-Fire Injection system used on it.” Forum member texaswilkins put even more miles on his. “Mine has almost 300,000 miles on it, and it still spins tires and pulls hard until way above the speed limit.” A thread from way back in 2009 has plenty of good things to say about this much-maligned system.

1984 Corvette Cross-Fire Injection

If you are lucky enough to live in a state where 1984 is beyond the reach of smog tests (or your testers aren’t very observant), you can correct GMs short shrift of the Cross-Fire motor. The aftermarket offers an intake manifold that solves the airflow problem and delivers up to 32 extra horsepower. The Renegade intake manifold manages to fit under the stock hood and air cleaner yet has a bigger plenum area and ports sized for proper performance. Yes, it will lower your fuel economy a little bit, but who cares when you suddenly are getting to 60 mph seconds faster.

What do you think of the Cross-Fire?

Bryan Wood is a longtime car and motorcycle enthusiast who writes for Harley-Davidson Forums and Corvette Forum, among other auto sites. Plus, he runs his own blog, Pilez & Driverz.

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