INFORMATION ON ELIMINATION OF VALVE SPRING SHIMMING. Cadillac Concours 1994

For 1990-2009 cars

# INFORMATION ON ELIMINATION OF VALVE SPRING SHIMMING

#### SUBJECT: INFORMATION ON ELIMINATION OF VALVE SPRING SHIMMING PROCEDURE

#### MODELS: 1993 CADILLAC ALLANTE 1993-95 CADILLAC ELDORADO AND SEVILLE 1994-95 CADILLAC DEVILLE CONCOURS WITH 4.6L NORTHSTAR ENGINE (VINS Y, D - RPOS LD8, L37)

1995 OLDSMOBILE AURORA WITH 4.0L ENGINE (VIN C - RPO L47)

WHENEVER SERVICING THE CYLINDER HEADS OF A 4.6L NORTHSTAR OR 4.0L AURORA ENGINE DO NOT USE SHIMS TO INCREASE VALVE SPRING LOAD AS STATED IN SECTION 6A2-ENGINE MECHANICAL OF THE APPROPRIATE SERVICE MANUAL.

THE TOLERANCES OF THE VALVE SPRINGS AT MAXIMUM CAMSHAFT LIFT DO NOT ALLOW ENOUGH CLEARANCE FOR THE ADDITIONAL HEIGHT OF A SHIM. THE ADDITION OF A SHIM WILL FORCE THE SPRING TO "BOTTOM-OUT" BEFORE THE CAMSHAFT IS AT PEAK LIFT AND CAUSE SERIOUS CYLINDER HEAD AND/OR VALVE TRAIN DAMAGE.

IF LOW VALVE SPRING LOAD IS FOUND DURING CYLINDER HEAD SERVICE, REPLACE THE VALVE SPRING. CURRENTLY, THE 1993-95 ENGINE MECHANICAL SECTIONS OF THE OLDSMOBILE AURORA AND CADILLAC ALLANTE, DEVILLE CONCOURS, SEVILLE AND ELDORADO SERVICE MANUALS CONTAIN THE VALVE SPRING SHIMMING PROCEDURE. THIS INFORMATION SHOULD BE OMITTED.

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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 1995. GENERAL MOTORS CORPORATION. ALL RIGHTS RESERVED.