INFO. ON COMPONENT/SERVICE PROCEDURE CHANGES

REVISION: 08/10/94

THIS BULLETIN IS BEING REVISED TO CORRECT "NEW SPECIFICATION" LISTED FOR THE HARMONIC BALANCER UNDER "FASTENER TORQUE SPECIFICATIONS." **********************************************************************

SUBJECT: INFORMATION ON COMPONENT AND SERVICE PROCEDURE CHANGES

MODELS: 1994-95 CADILLAC CONCOURS, ELDORADO AND SEVILLE WITH 4.6L NORTHSTAR ENGINE (VINS Y, 9 - RPOS LD8, L37)

FOLLOWING IS A LIST OF CHANGES AFFECTING COMPONENTS AND/OR SERVICE PROCEDURES. THESE CHANGES WILL BE REFLECTED IN THE PROCEDURES AND INFORMATION FOUND IN THE 1995 PRELIMINARY SERVICE MANUAL.

CAMSHAFT DRIVE SPROCKETS

ALL CAMSHAFT DRIVE SPROCKETS NOW HAVE A "SHOT-BLASTED" OR DULL/ROUGH FINISH INSTEAD OF THE PREVIOUS SHINY, MACHINED FINISH. THIS CHANGE OCCURRED DURING THE 1994 MODEL YEAR AND WILL CONTINUE UNTIL FURTHER NOTIFICATION. BECAUSE THIS IS A RUNNING CHANGE, SOME ENGINES MAY HAVE BEEN BUILT WITH BOTH THE "SHINY" AND "ROUGH" FINISH SPROCKETS. INTERMIXING THE SPROCKETS DOES NOT AFFECT ENGINE PERFORMANCE OR DURABILITY. IN ADDITION, THE TIMING MARK ON THE INTERMEDIATE SPROCKET WILL BE CHANGED FROM A CIRCLE TO AN ELLIPSE.

OTHER THAN MANUFACTURING PROCESS CHANGES RESULTING IN THE NEW LOOK AND FINISH, THE SPROCKETS ARE NO DIFFERENT FROM THOSE USED IN EARLY 1994.

COOLANT PLUG ELIMINATION FROM ENGINE BLOCK

ENGINE COOLANT DRAIN PLUGS, LOCATED ON EITHER SIDE OF THE ENGINE BLOCK BELOW THE CYLINDER HEADS, ARE ELIMINATED BEGINNING WITH THE 1995 MODEL YEAR.

LOST CORE FLUID INDUCTION SYSTEM (FIS)

A NEW PLASTIC INTAKE MANIFOLD ASSEMBLY WILL BECOME STANDARD ON THE 1995 MODEL YEAR NORTHSTAR ENGINE. THE MANIFOLD HOUSES THE FUEL INJECTORS, FUEL RAIL AND IS MAINLY COMPRISED OF THE INTAKE RUNNERS. THE MANIFOLD ELIMINATES THE MAGNESIUM HOUSING FOUND ON THE 1994 MODEL YEAR ENGINE AND IS HELD IN PLACE WITH 10 BOLTS INSTEAD OF THE 4 BOLTS REQUIRED TO HOLD THE 1994 FIS ASSEMBLY.

PISTON WRIST PIN

A NEW PISTON WRIST PIN WAS INTRODUCED DURING THE 1994 MODEL YEAR. THE WALL THICKNESS OF THE NEW WRIST PIN IS CONSTANT THROUGHOUT THE LENGTH OF THE PIN. THE PREVIOUS DESIGN WRIST PIN HAD A FORMED "STEP." THE STEP IS A RIDGE LOCATED AT THE CENTER OF THE PIN THAT IS APPROXIMATELY 3/8" LONG (SEE FIGURE 1).

POWDERED METAL CONNECTING RODS

THE CONNECTING RODS ARE NOW COMPOSED OF FORGED POWDERED METAL RATHER THAN FORGED STEEL. DURING THE MANUFACTURING PROCESS, THE CONNECTING RODS ARE ACTUALLY CAST AS ONE PIECE AND THE CAPS ARE SEPARATED FROM THE REST OF THE ROD ON A SCRIBED PARTING LINE. THESE RODS CAN BE IDENTIFIED BY THE USE OF BOLTS VERSUS A STUD AND NUT COMBINATION TO HOLD THE CAP ON THE CRANKSHAFT (SEE FIGURE 2).

THE POWDERED METAL CONNECTING RODS SHOULD **NEVER** BE USED IN CONJUNCTION WITH THE PREVIOUS DESIGN FORGED STEEL CONNECTING RODS BECAUSE OF MASS DIFFERENCES BETWEEN THE TWO DESIGNS.

WATER PUMP

A NEW WATER PUMP, WHICH HAS LARGER VANES, WILL BE INCORPORATED IN THE 1995 NORTHSTAR ENGINE. ALSO, A NEW SPECIAL SERVICE TOOL, NUMBER J 38816-A, FOR THE REVISED WATER PUMP WILL BE AVAILABLE SOON.

REVISED OIL FILTER ADAPTER MOUNTING BOLT

A NEW OIL FILTER ADAPTER MOUNTING BOLT WAS INTRODUCED DURING THE 1994 MODEL YEAR AND IS USED IN ALL 1995 MODEL YEAR ENGINES. THE NEW BOLT HAS A CAPTURED CONICAL-SPRING TYPE WASHER AND SHOULD BE USED IN PLACE OF THE PREVIOUS STYLE FASTENER, REGARDLESS OF MODEL YEAR, WHEN SERVICING THE OIL FILTER ADAPTER. IN ADDITION, THE TORQUE SPECIFICATION FOR THE BOLT IS NOW 16 N.M (12 LBS. FT.) VERSUS THE PREVIOUS DESIGN SPEC OF 25 N.M (18 LBS. FT.). ORDER THE NEW FASTENERS UNDER PART NUMBER 3546520.

REVISED OIL PUMP ASSEMBLY

BEGINNING WITH THE START OF PRODUCTION FOR THE 1995 MODEL YEAR, A NEW, LOWER CAPACITY OIL PUMP WILL BE USED ON 4.6L ENGINES. THE PUMP CAN BE IDENTIFIED BY A CHANGE IN DRIVE SPACER DESIGN. THE REVISED VERSION HAS SMALLER OUTSIDE DIAMETER AND TWO MACHINED FLATS TO DRIVE THE PUMP, WHILE THE PREVIOUS VERSION HAS A LARGER OUTSIDE DIAMETER AND ONE MACHINED FLAT FOR PUMP DRIVE (SEE FIGURE 3).

THE NEW LOWER CAPACITY PUMP **CAN BE** USED IN ENGINES ORIGINALLY EQUIPPED WITH THE HIGHER CAPACITY PUMP, HOWEVER, YOU **MUST** USE THE NEW DESIGN DRIVE SPACER ALONG WITH THE NEW LOWER CAPACITY PUMP.

FASTENER TORQUE SPECIFICATIONS

THE TORQUE SPECIFICATION FOR THE OIL FILTER ADAPTER AND THE HARMONIC BALANCER FASTENERS HAS BEEN REVISED. THE REVISED SPECIFICATIONS FOR THESE FASTENERS ARE AS FOLLOWS:

FASTENER NEW SPECIFICATION OLD SPECIFICATION -------- ----------------- ----------------- HARMONIC BALANCER 60 N.M (44 LBS. FT.) + 145 N.M (105 LBS. FT.) + 120 DEGREES 120 DEGREES

OIL FILTER ADAPTER 16 N.M (12 LBS. FT.) 25 N.M (18 LBS. FT.)

FIGURES: 3

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.

COPYRIGHT 1994. GENERAL MOTORS CORPORATION. ALL RIGHTS RESERVED.