Cadillac Engine >> ENGINE INSTALLATION CAUTION

Cadillac Engine >> ENGINE INSTALLATION CAUTION

Engine Installation Caution on
1981 GM 6.0L (368 CID) 4-6-8 Equipped Vehicles


AERA members should exercise special caution when installing 1981
GM 6.0L (368 CID) 4-6-8, or modulated displacement engines into
Cadillac manufactured vehicles.

The 4-6-8 engine was designed by Cadillac to turn off 2 or 4
cylinders at a time during reduced load conditions to increase
fuel economy. Reducing the number of active cylinders is
accomplished through valve selector solenoids to control whether
a valve will open or remain closed. While the piston still
travels up and down in the cylinder, both intake and exhaust
valves remain closed when the cylinder is deactivated.

Frequent owner complaints finally lead most dealerships to
disconnect those parts of the system that controlled cylinder
deactivation, permitting the engine to operate on 8 cylinders all
of the time.

AERA members have reported installing engines into these vehicles
and reconnecting all of the electrical connectors found in the
engine compartment. This has led to erratic engine operation
caused by attaching sensors that specifically dealt with the
modulated displacement option. It is therefore extremely
important to tag all electrical connections, even those that are
not attached to a sensor or other component.


The AERA Technical Committee


November 1989 - SB 173


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