For 1990-2009 cars

# NEW CYLINDER HEAD GASKET/BOLTS TIGHTENING PROC: SMU

REVISION: 08/15/94

THIS BULLETIN IS REVISED TO ADD CUTLASS SUPREME AND GRAND PRIX TO THE LISTING OF MODELS.

THIS BULLETIN IS REVISED TO EXPAND MODEL YEAR APPLICATION AND INCLUDE W CAR APPLICATIONS. PREVIOUS DIVISIONAL PUBLICATION NUMBERS WERE:

CHEVROLET 93-51-6A BUICK 93-6-5 OLDSMOBILE 93-U-14 PONTIAC 93-6-15

THIS BULLETIN SUPPLEMENTS THE CLEANING PROCEDURE FOR THE SPECIAL POLICIES:

CANADA 3S04A CHEVROLET 91-525-6A BUICK 91-POL-2A OLDSMOBILE 91-T-244A PONTIAC 91-SM-4B * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

#### SUBJECT: SERVICE MANUAL UPDATE - SECTION 6A7 - NEW CYLINDER HEAD TIGHTENING AND FLATNESS SPECIFICATIONS AND CLEANING PROCEDURE

#### MODELS: 1988-94 BUICK SKYLARK 1992-94 CHEVROLET BERETTA 1987-91 OLDSMOBILE CUTLASS CALAIS 1990-91 OLDSMOBILE CUTLASS SUPREME 1992-94 OLDSMOBILE ACHIEVA 1988-94 PONTIAC GRAND AM 1990-91 PONTIAC GRAND PRIX WITH 2.3L ENGINE (VINS A, D AND 3 - RPOS LG0, LD2 AND L40)

THERE ARE NEW CYLINDER HEAD FASTENER TIGHTENING SPECIFICATIONS FOR THE 1992-93 QUAD ENGINES. CYLINDER HEAD FLATNESS SPECIFICATIONS AND CLEANING PROCEDURES FOR 1987-94 QUAD ENGINES ARE ALSO INCLUDED. PLEASE ADD THIS PROCEDURE TO SECTION 6A7 IN THE APPLICABLE SERVICE MANUAL.

THE CYLINDER HEAD TIGHTENING SPECIFICATIONS AND PROCEDURES ARE THE SAME FOR ALL 1987-94 QUAD ENGINES. THIS BULLETIN SUPPLEMENTS THE CLEANING PROCEDURE FOR THE SPECIAL POLICIES LISTED ABOVE.

1. REMOVE CYLINDER HEAD ASSEMBLY, REFER TO SECTION 6A7 IN THE APPLICABLE SERVICE MANUAL.

2. DISASSEMBLE, CLEAN AND INSPECT THE TENSIONER ASSEMBLY. BE SURE TO PAY SPECIAL ATTENTION TO THE OIL FEED AND DRAIN HOLES. MAKE SURE THE OIL HOLES ARE FREE OF DIRT SO THEY WILL ALLOW PROPER OIL FLOW. IF THERE IS VARNISH IN THE TENSIONER BORE OR ON THE PLUNGER THAT MAY CAUSE THE PLUNGER TO STICK IN THE BORE, **LIGHTLY** POLISH THE PLUNGER OR BORE WITH SCOTCH BRITE OR EQUIVALENT. CLEAN ALL PARTS BEFORE ASSEMBLY. DO NOT USE ANY OTHER METHOD OR TECHNIQUE TO CLEAN THE PLUNGER OR BORE. SMOOTH SURFACES WILL ENSURE THE PLUNGER WILL NOT STICK IN THE BORE. IF THE PLUNGER STILL DOES NOT OPERATE SMOOTHLY, REPLACE THE PARTS. STORE THE TENSIONER ASSEMBLY UNTIL IT IS NEEDED FOR ASSEMBLY IN A LOCATION (E.G., THE PARTS CLEANER) WHERE DIRT WILL NOT GET INTO THE OIL HOLES. **DO NOT USE ANY CLEANING MATERIAL OR METHOD THAT WILL REMOVE METAL FROM THE PLUNGER OR BORE.**

3. INSPECT THE CYLINDER HEAD BOLTS FOR DAMAGED THREADS OR FOR DAMAGED HEADS CAUSED BY IMPROPER USE OF TOOLS. REPLACE HEAD BOLTS IF NECESSARY.

#### NOTICE: DO NOT USE ABRASIVE PADS TO CLEAN THE CYLINDER HEAD OR BLOCK SURFACES. AN ABRASIVE PAD MAY DAMAGE THE CYLINDER HEAD OR BLOCK. ABRASIVE PADS SHOULD NOT BE USED FOR THE FOLLOWING REASONS:

* ABRASIVE PADS WILL PRODUCE A FINE GRIT THAT THE OIL FILTER WILL NOT BE ABLE TO REMOVE FROM THE OIL. THIS GRIT IS ABRASIVE AND HAS BEEN KNOWN TO CAUSE INTERNAL ENGINE DAMAGE. ABRASIVE PADS CAN EASILY REMOVE ENOUGH MATERIAL TO ROUND CYLINDER HEAD SURFACES. THIS HAS BEEN KNOWN TO AFFECT THE GASKET'S ABILITY TO SEAL, ESPECIALLY IN THE NARROW SEAL AREAS BETWEEN THE COMBUSTION CHAMBERS AND COOLANT JACKETS. THE CYLINDER HEAD GASKET IS LIKELY TO LEAK IF THESE EDGES ARE ROUNDED.

* ABRASIVE PADS CAN ALSO REMOVE ENOUGH METAL TO AFFECT CYLINDER HEAD FLATNESS. IT TAKES ABOUT 15 SECONDS TO REMOVE 0.203 MM (0.008") OF METAL FROM THE CYLINDER HEAD WITH AN ABRASIVE PAD. IF CYLINDER HEAD FLATNESS IS OUT OF SPECIFICATION, THE GASKET WILL NOT BE ABLE TO SEAL AND THE GASKET WILL LEAK.

4. THOROUGHLY CLEAN THE CYLINDER HEAD AND BLOCK SURFACES.

A. CAREFULLY REMOVE ALL GASKET MATERIAL. USE A RAZOR BLADE TYPE SCRAPER, REFER TO FIGURE 1.

* USE A **NEW** RAZOR BLADE FOR EACH CYLINDER HEAD. HOLD THE BLADE AS PARALLEL TO THE GASKET SURFACE AS POSSIBLE. THIS WILL ENSURE THAT THE RAZOR BLADE DOES NOT GOUGE OR SCRATCH THE GASKET SURFACES.

* BE CAREFUL NOT TO GOUGE OR SCRATCH THE GASKET SURFACES.

* DO NOT GOUGE OR SCRAPE THE COMBUSTION CHAMBER SURFACES.

**THE ABOVE PROCEDURE IS THE BEST METHOD FOR REMOVING GASKET MATERIAL FROM THE CYLINDER HEAD GASKET SURFACES. THE PREVIOUSLY PUBLISHED PROCEDURE USING CHEMICAL GASKET REMOVERS AND A WOOD OR PLASTIC SCRAPER IS ACCEPTABLE TOO.**

**DO NOT USE ANY OTHER METHOD OR TECHNIQUE TO REMOVE GASKET MATERIAL.**

#### IMPORTANT: THE APPEARANCE OF THE GASKET SURFACE IS NOT IMPORTANT - THE FEEL IS. THERE WILL BE INDENTATIONS FROM THE GASKET LEFT IN THE CYLINDER HEAD AFTER ALL THE GASKET MATERIAL IS REMOVED. THESE SMALL INDENTATIONS WILL BE FILLED IN BY THE NEW GASKET.

B. CHECK CYLINDER HEAD FOR FLATNESS. REFER TO SERVICE MANUAL SECTION 6A7 FOR CYLINDER HEAD CHECKING PROCEDURE. USE THE FOLLOWING SPECIFICATIONS.

SPECIFICATION RESURFACE REUSE ------------- --------- ----- LESS THAN 0.076 MM (0.003") NO YES 0.076 - 0.25 MM (0.003 - 0.010") YES YES OVER 0.025 MM (0.010) NO DISCARD

5. INSPECT THE CYLINDER HEAD SURFACE FOR CORROSION OR CRACKS. THE COMBUSTION SEAL AREA WILL LEAVE A "SHADOW" MARK ON THE CYLINDER HEAD (SHADED AREA - FIGURE 1). IF CORROSION IS EVIDENT OUTSIDE OF THE OUTSIDE DIAMETER (OD) OF THE COMBUSTION SEAL AREA (SHADED AREA - FIGURE 2), THE CYLINDER HEAD MAY BE REUSED.

IF ANY CORROSION EXTENDS INTO THIS SHADED AREA AND/OR IF CRACKS ARE FOUND, THE CYLINDER HEAD SHOULD BE REPLACED.

#### IMPORTANT: DO NOT USE A TAP TO CLEAN THE HEAD BOLT HOLES.

6. CLEAN EACH HEAD BOLT SEAT BOSS ON THE CYLINDER HEAD. CLEAN THE BOLT HOLES IN THE CYLINDER BLOCK, REFER TO FIGURE 3. USE A NYLON BRISTLE BRUSH TO CLEAN THE BOLT HOLE THREADS, REFER TO FIGURE 4. MAKE SURE THAT ALL PUDDLES OF OIL AND COOLANT HAVE BEEN REMOVED FROM BOLT HOLES OTHERWISE THE TIGHTENING SEQUENCE WILL NOT OBTAIN THE PROPER CLAMP LOAD BECAUSE OF HYDROSTATIC LOCK. **IF THE BOLT HOLES ARE NOT CLEANED, THE HEAD GASKET MAY LEAK.**

7. APPLY CLEAN ENGINE OIL SPARINGLY TO THE THREADS AND THE BOTTOM SIDE OF THE FLANGE OF THE BOLT (FIGURES 5 AND 6).

#### NOTICE: THE FOLLOWING TIGHTENING PROCEDURE MUST BE USED TO ENSURE GASKET LIFE. FAILURE TO FOLLOW THIS PROCEDURE EXACTLY MAY RESULT IN CYLINDER HEAD GASKET LEAKAGE.

8. INSTALL AND TIGHTEN CYLINDER HEAD BOLTS TO THE N.M (LB. FT.) SPECIFICATION IN SEQUENCE. REFER TO FIGURE 7.

9. AFTER COMPLETING STEP A ON ALL TEN BOLTS, TIGHTEN THE CYLINDER HEAD BOLTS (USING J 36660) THE ADDITIONAL DEGREES INDICATED IN FIGURE 7 IN SEQUENCE.

10. ASSEMBLE THE REST OF THE ENGINE, REFER TO SECTION 6A7 IN THE APPLICABLE SERVICE MANUAL.

FIGURES: 07

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.

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