Cadillac produced the 4.9-liter V-8 engine to essentially fill a gap as Cadillac transitioned from the 4.5-liter V-8 that powered the 1988 to 1993 Allante, to the 4.9-liter Northstar engine launched to power all Cadillacs beginning in 1994. The 4.9-liter V-8 was a vast improvement over the early 4.5 V-8s because it featured a port fuel-injection system that reduced emissions.
Cadillac introduced the 4.5-liter V-8 in 1988 with throttle-body fuel injection, or TBI, and then switched to a port fuel injection system in 1990. Through 1990, the 4.5 powered the Cadillac Seville, Allante, DeVille, Eldorado and Fleetwood. The 4.9-liter V-8, which was a larger version of the 4.5 with virtually the same internal components, took over in 1991. The 4.5-liter's port fuel injection system is identified by "V8 PFI" emblazoned on the valve cover, and by the injectors and fuel rails on the intake manifold. With the TBI system, the 4.5 generated up to 200 horsepower. The 1990 4.5 equipped with PFI generated 180 horsepower. Cadillac used the 4.9 through 1995 and matched it with a 4T60E electronic shift four-speed automatic transmission housed in an aluminum case. The automatic was an improvement over the non-electronic shift 4T60 transmission that matched the 4.5.
Cadillac equipped all 4.9-liter V-8s with port fuel injection. The new system replaced the 1980s General Motors TBI system. The TBI version used two injectors in the throttle body, while the PFI version used eight injectors in the intake manifold with one injector mounted on each intake valve and a fuel rail delivering the fuel to each injector. The injector sprayed fuel before and during each intake valve opening. By having separate injectors deliver fuel to each cylinder, the engine was more efficient because it reduced emissions by minimizing uneven fuel distribution and condensation.
The Cadillac port fuel injection 4.9-liter V-8 had a squared 3.623-inch bore and 3.623-inch stroke. It featured a 9.5-to-1 compression ratio to provide 200 horsepower and 275 foot-pounds of torque. The torque was a boost over the torque rating of the 4.5, which was 240 foot-pounds. In 1991, Cadillac installed on the 4.9 a stronger oil pump that increased oil flow by 13 percent and pressure by 18 percent. It also featured a new oil pan and baffle to minimize oil starvation that was a problem in the 4.5-liter V-8. The 4.5 had a reputation for being noisy when the engine was cold. Cadillac gave the 4.9's pistons a different profile that reduced noise in cold weather conditions.
Cadillac's launch of the more compact and powerful Northstar 4.6-liter V-8 in 1992 -- for the 1993 Allante -- doomed the 4.9 V-8. The 4.6 initially powered the last of the Allantes, and then expanded to other Cadillacs in 1994, with 295 horsepower and 290 foot-pounds of torque. By 1995, it developed 300 horsepower, forcing the 4.9 out of production.
