NEW HEAD BOLT TORQUING PROCEDURE

NEW HEAD BOLT TORQUING PROCEDURE

VEHICLES AFFECTED: 1988 S/T WITH 2.5L (VIN CODE E) OR 2.8L (VIN CODE R) ENGINES

On 1988 S/T trucks with the 2.5L and 2.8L engines, the head bolt torquing has been changed to the Dynamic Torque (torque bolt to specified torque and then rotate bolts a specified distance) method.

If it becomes necessary to remove and reinstall the cylinder head on 1988 S/T models equipped with these engines, the following procedures must be followed to ensure correct bolt installation.

Service Procedures

2.5L L4 ENGINES

1. Install cylinder head using a new gasket.

2. Clean all bolts

3. Coat threaded portion of bolts 1, 2, 3, 4, 5, 6, 7, 8 and 10 with engine oil. Apply sealant, P/N 992545 or equivalent threaded portion of bolt Number 9.

4. Install all bolts and torque in sequence (See Figure No. 1 to 25 Nm (18 lb ft).

5. Retorque bolts 1, 2, 3, 4, 5, 6, 7, 8 and 10 to 35 Nm (27 lb ft). Retorque bolt 9 to 25 Nm (18 lb ft).

6. Draw a line across the head of each bolt with a marking crayon to mark the position of each bolt, see Figure 1.

7. Following the same sequence, tighten all bolts an additional 90 degrees (1/4 turn).

2.8L V6 ENGINE

1. Install cylinder head using a new gasket.

2. Clean all bolts.

3. Apply sealer, P/N 992545, or equivalent to the threaded portion of bolts.

4. Install bolts and torque in sequence (See Figure No. 2) to 55 Nm (40 lb ft).

5. Draw a line across the head of each bolt with a marking crayon to mark the position of each bolt, see Figure 2.

6. Using the same sequence, tighten bolts an additional 90 degrees (1/4 turn).

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.