1996 Corvette LT4: Recall: Rocker Arm Attaching Pin Not Fully Seated

Model Year: 1996 Corvettes With LT4 Engine
Subject: INADEQUATE RETAINING LOAD HOLDING ROCKER ARM ROLLER PIN IN PLACE
Source: Chevrolet Product Campaign
Number: 96-C-07A

TO: ALL CHEVROLET DEALERS

General Motors has decided that CERTAIN 1996 Chevrolet Corvettes equipped with 5.7L engines (RPO LT4 - VIN Code "5") may have been built with rocker arms that have inadequate retaining load to hold roller attaching pins in the rollers. When there is inadequate retaining load, the pin may back out, with a resultant engine failure likely to occur.

To correct this condition, dealers are to replace the rocker arms.

NOTICE: Previously received rocker arms P/N 12551311 must not be used. The rocker arms previously received should have been returned to GMSPO (reference GMSPO Information Bulletin #96-128). Any vehicles previously repaired with P/N 12551311 rocker arms as a result of the canceled Campaign No. 96-C-07 must have new rocker arms installed.

VEHICLES INVOLVED

Involved are certain 1996 Chevrolet Corvettes equipped with 5.7L (RPO LT4) engines built within the following VIN breakpoints:

Involved vehicles have been identified by Vehicle Identification Number Computer Listings. Computer listings contain the complete Vehicle Identification Number, owner name and address data, and are furnished to involved dealers with the campaign bulletin. Owner name and address data furnished will enable dealers to follow-up with owners involved in this campaign.

These listings may contain owner names and addresses obtained from State Motor Vehicle Registration Records. The use of such motor vehicle registration data for any other purpose is a violation of law in several states. Accordingly, you are urged to limit the use of this listing to the follow-up necessary to complete this campaign. Any dealer not receiving a computer listing with the campaign bulletin has no involved vehicles currently assigned.

PARTS INFORMATION

Notice: -------

A pre-shipment of part numbers 12557779 (Rocker Arms) and 10108625 (Rocker Cover Gaskets) will be sent to involved dealers of record the week of May 6, 1996. Pre-shipment will equal parts for approximately 40% of the number of assigned vehicles to be repaired. Pre-shipment parts will be charged to the dealers open parts account.

Parts are to be obtained from General Motors Service Parts Operations (GMSPO). Please refer to your "Involved Vehicle Listing" prior to ordering requirements. Normal orders should be placed on a DRO = Daily Replenishment Order. An emergency requirement should be ordered on a CSO = Customer Special Order.

Quantity/ Part Number Description Vehicle ----------- ----------- ---------

12557779 Rocker Arm Assembly 16

10108625 Gasket, Rocker Cover 2

OWNER NOTIFICATION

Owners will be notified of this campaign on their vehicles by Chevrolet Motor Division (see copy of owner letter included with this bulletin).

DEALER CAMPAIGN RESPONSIBILITY

All unsold new vehicles in dealers, possession and subject to this campaign must be held and inspected/repaired per the service procedure of this campaign bulletin before owners take possession of these vehicles.

Dealers are to service all vehicles subject to this campaign at no charge to owners, regardless of mileage, age of vehicle, or ownership, from this time forward.

Owners of vehicles recently sold from your new vehicle inventory with no owner information indicated on the dealer listing, are to be contacted by the dealer, and arrangements made to make the required correction according to the instructions contained in this bulletin. This could be done by mailing to such owners a copy of the owners letter accompanying this bulletin. Campaign follow-up cards should not be used for this purpose, since the owner may not as yet have received the notification letter.

In summary, whenever a vehicle subject to this campaign enters your vehicle inventory, or is in your dealership for service in the future, please take the steps necessary to be sure the campaign correction has been made before selling or releasing the vehicle.

SERVICE PROCEDURE

ROCKER COVER REMOVAL

LH SIDE

1. Note setting of all electrical devices and then disconnect battery.

2. Remove fuel rail beauty cover.

3. Remove booster vacuum hose from intake manifold.

4. Remove distributor vent hose from intake manifold.

5. Remove fuel rail cover attaching studs.

6. Remove hoses (2) from A.I.R. check valve.

7. Loosen A.I.R. check valve tube at exhaust manifold and pivot away from rocker cover.

8. Remove air cleaner assembly.

9. Remove accessory drive belt.

10. Remove generator bolts and rear bracket and lay generator aside.

11. Remove rocker cover bolts (4) and cover. Both rocker cover gaskets should replaced with new gasket P/N 10108625.

RH SIDE

1. Remove fuel line beauty cover.

2. Remove PCV fresh air hose.

3. Remove rocker cover bolts (4) and cover.

ROCKER ARM REMOVAL AND REPLACE

1. Rotate engine clock wise to TDC number 1 cylinder firing position. This can be done by watching number 1 cylinder valves as crankshaft balancer hub arrow approaches the 12 o’clock position. If a valve moves as arrow moves to the 12 o’clock position, the engine assembly is in the number 6 cylinder firing position. Crankshaft must then be turned one more revolution to reach number 1 cylinder firing position.

2. In this #1 firing position the following rocker arms should be replaced with new rocker arms P/N 12557779:

Exhaust 1,3,4,8 Intake 1,2,5,7

3. Loosen rocker arm nut and lift rocker arms from stud.

4. Install new rocker arms P/N 12557779. Be sure push rod is properly seated in the lifter and rocker arm.

5. Install nuts and torque to 25 Nm (18 lb. ft.).

6. Rotate engine clock wise one more revolution until hub arrow is again at 12 o’clock position. This is a number 6 cylinder firing position.

7. In this #6 firing position the following rocker arms should be replaced with new rocker arms P/N 12557779:

Exhaust 2,5,6,7 Intake 3,4,6,8

8. Repeat steps 3 through 6.

9. After rocker arm installation be sure that the roller tip of the rocker arm is squarely seated on top of valve stem. (Refer to 1996 Corvette Preliminary Service Manual Section 6AlB-l3, Figure 14).

ROCKER COVER INSTALLATION

RH SIDE

1. Install rocker cover and bolts (4). Torque bolts to 12 Nm (106 lb. in). New rocker cover gaskets P/N 10108625 should be used.

2. Install PCV fresh air hose.

3. Install fuel line beauty cover.

LH SIDE

1. Install rocker cover and bolts (4). Torque bolts to 12 Nm (106 lb. in). New rocker cover gaskets P/N 10108625 should be used.

2. Install generator, generator bolts, and rear bracket. Torque front generator bolts and bolt with nut to 50 Nm (3 7 lb. f t) Torque rear bolts and bracket bolt to 47 Nm (35 lb. ft).

3. Tighten A.I.R. check valve tube at exhaust manifold and torque to 55 Nm (41 lb. ft).

4. Install hoses (2) from A.I.R. check valve.

5. Install booster vacuum hose to intake manifold.

6. Install distributor vent hose to intake manifold.

7. Install fuel rail cover attaching studs. Torque studs to 12 Nm (106 lb. in.).

8. Install fuel rail beauty cover.

9. Install accessory drive belt.

10. Install air cleaner assembly.

11. Connect battery and reset all electrical devices as noted in Step 1.

12. Install Campaign Identification Label.

CAMPAIGN IDENTIFICATION LABEL

Each vehicle corrected in accordance with the instructions outlined in this Product Campaign Bulletin will require a "Campaign Identification Label". Each label provides a space to include the campaign number and the five (5) digit dealer code of the dealer performing the campaign service. This information may be inserted with a typewriter or a ball point pen.

Each "Campaign Identification Label" is to be located on the radiator core support in an area which will be visible when the vehicle is brought in for periodic servicing by the owner. When installing the new Campaign Identification Label, be sure to install the clear protective covering. Additional Campaign Identification Labels can be obtained from VISPAC Incorporated by calling 1-800-269-5100 (Monday-Friday, 8:00 a.m. to 4:30 p.m. EST). Ask for Item Number S-1015 when ordering.

Apply "Campaign Identification Label" only on a clean, dry surface.

CLAIM INFORMATION

Submit a Product Campaign Claim with the information indicated below:

PART FAILED PARTS LABOR LABOR REPAIR PERFORMED COUNT PART NO. ALLOW CC-FC OP HOURS ---------------- ----- ------- ------ ----- ----- ------

Rocker Arm 18 12557779 ** MA-96 V9790 1.1* Replacement

* For Campaign Administrative Allowance, add 0.1 hours to the "Labor Hours".

** The "Parts Allowance" should be the sum total of the current GMSPO Dealer Net price plus 40’6 for the rocker arms and rocker cover gaskets needed to complete the repair.

Refer to the General Motors Corporation Claims Processing Manual for details on Product Campaign Claim Submission.

May, 1996

Dear Chevrolet Corvette Customer:

This notice is sent to inform you that Chevrolet Motor Division is conducting a recall campaign that includes your vehicle.

REASON FOR THIS RECALL

General Motors has determined that certain 1996 Chevrolet Corvettes equipped with 5.7L (RPO LT4) engines may have been built with rocker arms that have inadequate retaining load to hold roller attaching pins in the rollers. When there is inadequate retaining load, the pin may back but, with a resultant engine failure likely to occur.

WHAT WE WILL DO

To correct this condition, dealers are to install new rocker arms in your engine. This service will be performed for you at no charge.

WHAT YOU SHOULD DO

Please contact your Chevrolet dealer as soon as possible to arrange a service date and so the dealer may order the necessary parts for the repair. Instructions for performing this service have been sent to your dealer and parts are available. Please contact your dealer to arrange a service date as soon as possible. You may ask your dealer if you wish to know how much time will be needed to schedule and process your vehicle.

The enclosed owner reply card identifies your vehicle. Presentation of this card to your dealer will assist in making the necessary correction in the shortest possible time. If you have sold or traded your vehicle, please let us know by completing the postage paid reply card and returning it to us.

We are sorry to cause you this inconvenience; however, we have taken this action in the interest of your continued satisfaction with our products.

Chevrolet Motor Division GENERAL MOTORS CORPORATION