Engine: Description and Operation

The V8-273/4.5L engine is new for 1988. The intake manifold is of the dual plane design, with runners arranged in two groups of four. Within each group, a cylinder draws an intake charge every 180 ° of crankshaft rotation. This regular interval between intake events allows the runner shape, length and area to be tuned for maximum volumetric efficiency. This increased efficiency has allowed the elimination of the grid heater located between the throttle body and intake manifold on 4.1L engines. The throttle body bores have been enlarged, and provide over 50 percent more flow area than the 4.1L engine. To aid in decreasing engine friction, the 4.5L incorporates roller lifters in the valve train. Friction is reduced by eliminating the sliding motion between the bottom surface of the lifter and the cam lobe.