Why GM’s Cross-Fire Engines Earned the Nickname Cease-Fire – Jalopnik

It’s not uncommon for cars (and the engines that power them) to be given nicknames by their fans (and haters). General Motors’ V8s are not immune to this phenomenon, with fan-approved examples like the 327 small-block Chevy Mighty Mouse and the big-block V8 Chevy Rat Motors. However, sometimes these nicknames arise from frustration that was apparently common among owners. Such is the case with the GM Cross-Fire of the early 1980s, which became (un)affectionately known in some circles as the Ceasefire.

General Motors coined the name Cross-Fire to describe the dual 48-millimeter throttle body Rochester fuel injection system found in its particularly sporty motorcycles. However, the design was primarily intended to save fuel and meet 1980s emissions standards. General Motors engineers hoped that the advanced capabilities of the carburetor’s Computer Command Control and the 750 cubic feet per minute flow rate of the dual throttle bodies would deliver on all fronts. Instead, the Cross-Fire V8 became known as perhaps the worst engine to ever power a Corvette – which is a bold statement considering the Blue Flame Six that powered the original Corvette.

Cross-Fire injection problems that gave rise to the Cease-Fire nickname mainly stemmed from a compromise regarding the intake system. To accommodate the limited space of the low hoods used in sports cars of the early 1980s, the intake was lowered and the runners shortened to fit underneath. This left the Cross-Fire injected LU5s with 165 hp and the L83 with 205, and those relatively low power ratings came without really improving fuel economy.

The Cross-Fire injection system made its debut atop the 350 cubic-inch L83 small-block V8, which was standard in the 1982 and 1984 Chevrolet Corvette. The 305 cubic-inch LU5, an option for Chevy Camaros and Pontiac Firebirds in 1982 and 1983, also received it. The gap in Corvette model years is not because there is another engine involved, but because there is technically no such thing as a 1983 Chevy Corvette.

The Cross-Fire design was a callback of sorts to the legendary 302 Cross-Ram engine. While the Cross-Ram design worked well for the high-revving, race-oriented 302, the Cross-Fire injection system did not provide significant benefits for the 1980s GM lineup. The dual throttle bodies, one designated for each bank of cylinders, struggled to provide enough fuel to feed both engines. The problem was low-speed airflow through the lowered intake, which led to poor fuel distribution between cylinders.

Two solutions have been devised as improvements. Adding more fuel to the mixture allowed all cylinders to get enough fuel. However, this solution negated any fuel economy gains promised by the new electronics. Another solution was to reduce the intake duct volume to speed up airflow. Because the intake manifold ports were about two-thirds as large as the corresponding ports on the cylinder heads, the system had better manners around town, but limited performance above 4,000 rpm. The limited revs and concessions to accommodate the weak 700-R4 automatic transmission allowed the 1984 Corvette to reach a top speed of just 125 mph.