Tune-Up - 5.7l v8 VIN [m] GMC Vandura I

ENGINE IDENTIFICATION

Engines can be identified by eighth digit of Vehicle Identification Number (VIN). Number is located on plate at top left corner of dashboard and at base of steering column on van models.

Engine code numbers are located at front of block, at right cylinder head.

VIN ENGINE CODES

TUNE-UP NOTES

Note. When performing tune-up procedures described in this article, the following notes and precautions must be observed

Due to changes and corrections, always refer to Engine Tune-Up Decal in engine compartment before attempting tune-up. In the event of a conflict between specifications given in this manual and decal specifications, decal specifications prevail.

For tune-up purposes, "Light Duty" refers to vehicles up to 8500 lbs. "Heavy Duty" refers to vehicles exceeding 8500 lbs.

When performing tune-up on vehicles equipped with a catalytic converter, do not allow or create a condition of engine misfire in one or more cylinders for an extended period of time. Damage to converter from overheating may occur due to loading with unburned fuel.

ENGINE COMPRESSION

When making compression checks, disconnect the ignition switch connector pink wire from high energy ignition system. With air cleaner removed and throttle and choke wide open, crank engine through at least four compression strokes.

COMPRESSION SPECIFICATIONS

VALVE CLEARANCE

All vehicles are equipped with hydraulic lifters. Lifters should be adjusted to 1 turn down from zero lash.

VALVE ARRANGEMENT

E-I-I-E-E-I-I-E (Both banks, front-to-rear)

FIRING ORDER & DISTRIBUTOR/PICKUP INFORMATION

The engine is equipped with a basic High Energy Ignition system.

Timing Mark & Firing Order: Timing Socket at 10 Degrees ATDC. Scheme 16

DISTRIBUTOR PICKUP COIL RESISTANCE

IGNITION TIMING

Note. Engines are equipped with a receptacle for magnetic probe timing lights, located 10° ATDC. DO NOT use this location for timing with a conventional light.

1. Connect an adapter between No. 1 spark plug wire or use an inductive type pickup. DO NOT puncture wires. Connect timing light according to manufacturer's instructions.
2. Check or adjust ignition timing with engine at normal operating temperature, distributor vacuum line disconnected and plugged. (Scheme 16)

TIMING SPECIFICATIONS

SPARK PLUG SPECIFICATION

SPARK PLUG SPECIFICATIONS

SPARK PLUG PART NUMBER

HIGH TENSION WIRE RESISTANCE

Carefully remove ends of wire from spark plug and distributor. Using an ohmmeter, check resistance while gently twisting wire. If resistance is not to specifications, or fluctuates from infinity to any value, replace cable.

RESISTANCE

IGNITION COIL SPECIFICATIONS

COIL RESISTANCE

COIL OUTPUT

CARBURETOR USAGE

CARBURETOR

FUEL PUMP SPECIFICATIONS

FUEL PUMP SPECIFICATIONS

MIXTURE SCREW PLUG REMOVAL

1. Remove carburetor from engine and drain fuel. Invert carburetor and make 2 parallel cuts in the throttle body on either side of the locator points beneath the idle mixture needle plug (manifold side) with a hacksaw.
2. The cuts should reach down to the steel plug but should not extend more than 1/8" beyond the locator points. The distance between the saw marks depends on the size of the punch to be used.
3. Place a flat punch at a point near the ends of the saw marks in the throttle body. Holding the punch at a 45° angle, drive it into the throttle body until casting breaks away, exposing the steel plug.
4. Holding a center punch vertical, drive it into the steel plug. Holding the punch at a 45° angle, drive out the steel plug.

BEST IDLE PROCEDURE

1. Set parking brake and block drive wheels. Remove air cleaner after engine reaches normal operating temperature. Place transmission in neutral and connect tachometer.
2. As a starting point, turn idle mixture screws in lightly to seat and then back out 2 turns. DO NOT turn screws tightly against seat or damage may result.
3. With engine running, choke open, and transmission in neutral, adjust idle speed to specification. Adjust mixture screws to obtain maximum RPM.
4. Readjust idle speed screw to specification and readjust mixture screws to obtain highest RPM. Turn ignition off, remove gauges and install air cleaner.

AUTOMATIC CHOKE

A hot air heated choke coil is used to provide the choke valve closing force for cold startup and for correct opening timing during warmup.

Checking Hot Air Choke

1. With the parking brake applied, drive wheels blocked, transmission in Park or Neutral, start the engine and allow the engine to warm up, visually checking to be certain the choke valve opens fully.
2. If the choke valve fails to open fully, momentarily touch the choke housing and hot air inlet pipe or hose to determine if sufficient heat is reaching the choke coil. WARNING: The choke housing and hot air inlet pipe or hose are "Hot" to the touch. Use care to prevent burning of hands.
3. If the choke housing and/or heat inlet are cool to the touch, check for loss of vacuum to the housing, restricted heat inlet in the choke housing or choke heat pipe, collapsed or deteriorated heat inlet hose, or restricted passages in the manifold choke heat stove. Replace or correct as necessary.

COLD (FAST) IDLE RPM

1. Place transmission in neutral. Move cam follower onto highest step of fast idle cam. Disconnect and plug vacuum hose to EGR valve, canister purge hose and purge signal hose at canister.
2. Start engine without touching throttle. Turn fast idle speed screw to adjust speed to specification.

Note. For choke information, see AUTOMATIC CHOKE under FUEL SYSTEM.

FAST IDLE SPEED

BASE IDLE RPM

Note. See engine compartment Emission Control Tune-Up Decal to prepare engine for idle speed adjustment.

1. With engine idling, twist idle screw in or out as necessary to obtain specified RPM. See «BASE IDLE (RPM)»(/gmc/vandura/i-1970-1996/remont/adjustments/#tune-up-57l-v8-vin-m) table.

BASE IDLE (RPM)

THROTTLE RETURN CONTROL ADJUSTMENT

1. On engines equipped with throttle return control, connect a hand vacuum pump to control diaphragm. With engine idling, apply sufficient vacuum to extend the plunger fully.
2. Open throttle slightly to allow plunger to fully extend. Screw plunger in or out as necessary to obtain specified RPM. See Throttle Return Control table.

THROTTLE RETURN CONTROL

A/C IDLE SPEED CONTROL SOLENOID (ISS)

Note. Not all models are equipped with an ISS.

1. Prepare vehicle for adjustments according to directions on Emission Label on vehicle. Disconnect solenoid and turn air conditioning off. Set curb idle speed with idle speed screw.
2. Connect solenoid. Disconnect A/C lead at compressor and turn A/C on. Place automatic transmission in "D" and manual transmission in neutral.
3. Open throttle to extend solenoid plunger. Turn solenoid screw to adjust RPM. Reconnect A/C lead.

EMISSION CONTROL

No emission control information is contained in this article. Please see the appropriate article in the EMISSIONS section.

ALTERNATOR SPECIFICATIONS

All models are equipped with Delco alternators with integral voltage regulators.

ALTERNATOR SPECIFICATIONS

ALTERNATOR REGULATOR SPECIFICATIONS

Regulators are Delco nonadjustable, integral with alternator.

REGULATOR SPECIFICATIONS

BATTERY SPECIFICATIONS

BATTERY

STARTER SPECIFICATIONS

All models are equipped with Delco overrunning clutch starters.

STARTER SPECIFICATIONS

BASIC SERVICE INTERVALS

REPLACEMENT INTERVALS

FLUID CAPACITIES

FLUID CAPACITIES

BELT TENSION ADJUSTMENTS

BELT ADJUSTMENT (1)

See also:
• AUTOMATIC CHOKE
• BASE IDLE (RPM)