SMU - SECTION 6A2 - CYLINDER HEAD FLATNESS MEASUREMENT

SUBJECT: SERVICE MANUAL UPDATE - SECTION 6A2 - CYLINDER HEAD FLATNESS MEASUREMENT

MODELS: 1993 CADILLAC ALLANTE 1993 CADILLAC ELDORADO AND SEVILLE WITH 4.6L NORTHSTAR ENGINE (VINS Y AND 9 - RPOS LD8 AND L37)

THIS BULLETIN REVISES THE DIMENSION, FOUND ON PAGE 6A2-39 OF THE 1993 SERVICE MANUALS, FOR THE MINIMUM ALLOWABLE CYLINDER DECK SURFACE HEIGHT AFTER CYLINDER HEAD RESURFACING.

THE DIMENSION BETWEEN THE COMBUSTION CHAMBER GAUGE PAD AND CYLINDER HEAD DECK SURFACE MUST BE 10.5 MM OR GREATER AFTER CYLINDER HEAD DECK RESURFACING. THE SERVICE MANUAL TEXT AND FIGURE 56 BOTH SHOW A DIMENSION OF 8.5 MM; THIS IS INCORRECT.

ALWAYS REMOVE THE MINIMUM AMOUNT OF MATERIAL TO REMOVE SURFACE MARKS AND/OR PROVIDE A FLAT SEALING SURFACE. ALSO, WHEN RESURFACING THE CYLINDER HEAD OF A NORTHSTAR ENGINE, IT IS ACCEPTABLE TO REMOVE A PORTION OF THE INTAKE VALVE SEAT TO ACHIEVE SUFFICIENT SURFACE FLATNESS. HOWEVER, YOU **MUST** NOT GO BEYOND THE 10.5 MM SPECIFICATION WHEN RESURFACING.

PLEASE NOTE THIS INFORMATION IN YOUR 1993 CADILLAC ALLANTE, ELDORADO, AND SEVILLE SERVICE MANUALS.

FIGURES: 1

GENERAL MOTORS BULLETINS ARE INTENDED FOR USE BY PROFESSIONAL TECHNICIANS ONLY. BULLETINS ARE WRITTEN TO INFORM THOSE TECH- NICIANS OF A CONDITION POSSIBLY OCCURRING ON THE VEHICLE, OR TO PROVIDE INFORMATION ASSISTING IN THE PROPER SERVICE OF A VEHICLE. PROPERLY TRAINED TECHNICIANS HAVE THE EQUIPMENT, TOOLS, SAFETY INSTRUCTIONS, AND TRAINING TO DO A JOB PROPERLY AND SAFELY. IF A CONDITION IS DESCRIBED, DO NOT ASSUME THE BULLETIN APPLIES TO ALL VEHICLES. SEE AN AUTHORIZED GM DEALER FOR INFORMATION ON WHETHER A SPECIFIC VEHICLE MAY BENEFIT FROM THE INFORMATION.

COPYRIGHT 1994. GENERAL MOTORS CORPORATION. ALL RIGHTS RESERVED.