SERVICE GUILD: NEW 2.3 QUAD 4 ENGINE SPECS.

THE NEW 2.3 LITRE QUAD 4 ENGINE (OPTION LD2 - VIN CODE D)

Vehicles Affected: 1988 "N" SERIES ----------------- The new Quad 4 will be an available engine for the 1988 "N" series. "4" means that there are four valves per cylinder. With its chain-driven double overhead camshafts, the Quad 4 is GM's first high production engine of its type ever.

ENGINE DESCRIPTION: ------------------- - 150 HP @ 5,200 rpm - 1.1 HP per cubic inch - 160 ft. lbs @ 4,000 rpm - 7,000 rpm red line - 9.5 to 1 compression ratio - Two overhead camshafts - Direct-acting lifters - Cylinder block - cast grey iron - Head, camshaft housings, oil pan, timing chain housing-aluminium - The Quad 4 is rated at 150 horsepower at 5,200 rpm. It produces nearly 1.1 horsepower-per-cubic inch which is an exceptional achievement for a production engine.

COMPONENT DESCRIPTION: ---------------------- - One of the most innovative elements of the Quad 4 is a manufacturing proces called "microsizing". This close-tolerance process is used on the cylinder block, cylinder bores, crankshaft bearing bores, and on the crankshaft and piston pin bores of the connecting rods. Micro- sizing produces the necessary finishes and geometry needed to meet the low friction design goals.

CRANKSHAFT: ----------- - The crankshaft is cast nodular iron with eight counterweights. - It is a rolled fillet crankshaft for additional strength. - It has a pressed on oil pump drive gear which is serviced separately. - It has an ignition reluctor wheel with seven notches machined into the number five counterweight. - It has a highly polished microfinish on rod and main bearing journals.

HEAD: ----- - Aluminium head with pressed in sintered iron valve guides and valve seats.

CAMSHAFT CARRIER HOUSING:

- Two piece camshaft carrier which utilizes camshaft bearing journals that are smaller than the camshaft lobes for reduced friction. The cam carrier halves seal together with a silicone bead seated in to a groove machined into the carrier.

OIL PUMP: -------- - Gerotor design driven by a steel gear on the crankshaft.

CONNECTING RODS: ----------------- - Floating piston pins retained by a wire ring on each end. - Connecting rods are forged steel with a bronze bushing for increased piston pin life. An oil cooling hole which indexes once per revolution with the connecting rod oil feed hole is drilled into the rod on the exhaust side.

PISTONS: ------- - Cast aluminium pistons. - 0.25mm (0.010") oversize pistons are available for service. - Piston pin bore is slightly offset to the exhaust side of the block to reduce skirt load on the power stroke. This results in quieter engine operation and increased durability.

IGNITION SYSTEM: --------------- - Under an attractive die cast cover is a unique ignition system. The ignition assembly cover also serves as a heat sink for the ignition module, which is mounted on the top of the engine between the two camshaft housings. The ignition module includes closed loop dwell control and limited backup spark timing control. The ignition is a fast-rise, two coil system with the coils bolted to the ignition assembly cover directly above the spark plugs. The Integrated Direct Ignition (IDI) module fits directly on to the spark plugs, eliminating spark plug wires. Service procedure is to apply release agent to the spark plug porcelain. Spark plug torque is 21-24 N.m (15-18 ft. lbs.) cold. Undertorqued spark plugs may loosen torque during heat cycles and loosen.

IGNITION SYSTEM: --------------- - Multiport fuel injection system with Rochester Products injectors. - A cold start injector is not needed.

FUEL DELIVERY: ------------- - 300 kpa/43 psi system pressure regulator and an extruded aluminium fuel rail.

******************** QUAD 4 SERVICE INFORMATION *****************

TIMING CHAIN: ------------- - The timing chain is a double-row roller chain designed to last for the life of the engine. A hydraulic tensioner and three guides control chain motion. The hydraulic tensioner is fed by engine oil. A burst of chain noise rattle may occur after overnight or a 1-2 hour hot soak. This is caused by a 1-2 second delay in engine oil pressure build-up to hydraulic chain tensioner.

OPERATING CHARACTERISTICS ON SHORT DRIVES:

- Milky deposits in crankcase.

In cold weather, repeated short trips with limited engine warm-up may allow moisture to accumulate in the engine oil. This can cause milky deposits to form on internal engine surfaces, and may be visible on the oil dipstick. Running the engine at full operating temperature dissolves the deposits, evaporates the moisture, allowing their removal through the engine vent system. There are no effects on engine durability or performance. This condition is not uncommon in other internal combustion engines.

NORMAL MAINTENANCE REPLACEMENT PARTS: -------------------------------------

Air Filter Element 2.3 Litre L-4 (Engine Code D )...................AC Type A-1088C GM Part # 25096763 Engine Oil Filter 2.3 Litre L-4 (Engine Code D)....................AC Type PF-40 or PF-47 GM Part # 6439929 or # 25010792 Spark Plugs 2.3 Liter L-4 (Engine Code D)........... AC Type FR3LS Gap 0.889mm (0.035") GM Part # 5613796

CAPACITIES AND SPECIFICATIONS: ------------------------------ Liters Quarts Cooling System 2.3 Liter L-4 (Engine Code D)..............7.20 7.60

Engine Crankcase 2.3 Liter L-4 (Engine Code D)..............3.78 4.00

Oil Viscosity API Oil Requirements are SF/CC or SF/CD....5W-30 Thermostat Temperature.....................91 degrees C (195 degrees F)

OIL PRESSURE: (5W30 OIL) ------------- Minimum Oil Pressure: 70kPa (10 psi) at 900 rpm 175kPa (25 psi) at 2000 rpm

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.