Lower Intake Manifold Replacement

Lower Intake Manifold Replacement

Removal Procedure

Important: This engine uses a sequential multiport fuel injection system. Injector wiring harness connectors must be connected to their appropriate fuel injector or exhaust emissions and engine performance may be seriously affected.







1. Remove the upper intake manifold. Refer to Upper Intake Manifold Replacement (Service and Repair).
2. Remove the valve rocker arm covers. Refer to Valve Rocker Arm Cover Replacement - Left Side (Valve Rocker Arm Cover Replacement - Left Side) and Valve Rocker Arm Cover Replacement - Right Side (Valve Rocker Arm Cover Replacement - Right Side).
3. Remove the coolant crossover pipe. Refer to Engine Coolant Crossover Pipe Replacement (LZ4) (Service and Repair).
4. Disconnect the fuel injector wiring harness electrical connector from the engine coolant temperature (ECT) sensor.




5. Disconnect the engine wiring harness electrical connector (2) from the fuel injector inline electrical connector.




6. Disconnect the fuel injector wiring harness electrical connector from the camshaft position (CMP) sensor.




7. Remove the fuel injector wiring harness connector bracket bolt from the intake manifold.




8. Remove the fuel rail bolts and rail (1).




9. Remove the lower intake manifold bolts.
10. Remove the lower intake manifold.




11. Loosen the rocker arm bolts.

Important: Place the valve train components in a rack in order to ensure that the components are installed in the same location from which they were removed.


12. Remove the rocker arms.
13. Remove the push rods.

* The intake push rods measure 147.51 mm (5.81 in).
* The exhaust push rods measure 154.87 mm (6.1 in).





14. Remove the lower intake manifold gaskets and seals.
15. Clean the lower intake manifold gasket and seal surfaces on the cylinder heads and the engine block.
16. Clean the gasket and seal surfaces on the lower intake manifold with degreaser.
17. Remove all the loose room temperature vulcanizing (RTV) sealer.



Installation Procedure

Important: All gasket-mating surfaces need to be free of oil and foreign material. Use cleaner to clean the surfaces. Refer to Sealers, Adhesives, and Lubricants (Specifications).








Important: RTV sealer is NOT to be placed under the lower intake manifold gaskets.


1. Install the lower intake manifold gaskets and seals.




2. Coat the ends of the push rods using prelube GM P/N 12345501 (Canadian P/N 992704) or equivalent.
3. Install push rods in their original location.

* The intake pushrods are identified with yellow stripes.
* The exhaust pushrods are identified with green stripes.

4. Coat the rocker arm friction surfaces using prelube GM P/N 12345501 (Canadian P/N 992704) or equivalent.

Important: Shims (P/N 88894006) may be required under the valve rocker arm pedestals if reconditioning has been performed on the cylinder head or its components.


5. Install the rocker arms in their original locations.

Notice: Refer to Fastener Notice (Fastener Notice).

6. Install the rocker arm bolts.

Tighten the bolts to 34 N.m (25 lb ft).





7. With the NEW gaskets and seals in place, apply a small drop, 8-10 mm (0.31-0.39 in) of RTV sealer to the 4 corners of the intake manifold to block joints (1). Refer to Sealers, Adhesives, and Lubricants (Specifications).
8. Install the lower intake manifold.





Notice: Maximum gasket performance is achieved when using new fasteners, which contain a thread-locking patch. If the fasteners are not replaced, a thread locking chemical must be applied to the fastener threads. Failure to replace the fasteners or apply a thread-locking chemical MAY reduce gasket sealing capability.


Notice: Failure to tighten vertical bolts before the diagonal bolts may cause an oil leak.

9. Apply sealer to the lower intake manifold bolt threads. Refer to Sealers, Adhesives, and Lubricants (Specifications).

Notice: Refer to Fastener Notice (Fastener Notice).

10. Install the lower intake manifold bolts.
11. Tighten the lower intake manifold bolts in the sequence shown.

1. Tighten the bolts (1, 2, 3, 4) in sequence to 16 N.m (12 lb ft).
2. Tighten the bolts (5, 6, 7, 8) in sequence to 25 N.m (18 lb ft).






12. Inspect the fuel rail, fuel injectors for damage and replace as necessary.
13. Lubricate and install NEW injector lower O-rings seals onto the injectors. Lubricate the NEW O-rings seals with GM P/N 12345616 (Canadian P/N 993182).
14. Install the injector nozzles into the lower intake manifold injector bores.
15. Press on the injector rail using the palms of both hands until the injectors are fully seated.
16. Install the fuel injector rail bolts.

Tighten the bolts to 14 N.m (10 lb ft).





17. Position the fuel injector wiring harness electrical connector bracket to the intake manifold and install the bolt.

Tighten the bolt to 14 N.m (10 lb ft).





18. Connect the fuel injector wiring harness electrical connector to the CMP sensor.




19. Connect the engine wiring harness electrical connector (2) to the fuel injector inline electrical connector.




20. Connect the fuel injector wiring harness electrical connector to the ECT sensor.
21. Install the coolant crossover pipe. Refer to Engine Coolant Crossover Pipe Replacement (LZ4) (Service and Repair).
22. Install the valve rocker arm covers. Refer to Valve Rocker Arm Cover Replacement - Left Side (Valve Rocker Arm Cover Replacement - Left Side) and Valve Rocker Arm Cover Replacement - Right Side (Valve Rocker Arm Cover Replacement - Right Side).
23. Install the upper intake manifold. Refer to Upper Intake Manifold Replacement (Service and Repair).