After overhaul, the engine must be tested before it is installed in the vehicle. If a suitable test stand is not available, the following procedure can be used after the engine is installed in the vehicle.

1. Lubricate the oil filter rubber seal with clean engine oil.
2. Install the oil filter.
3. Fill the crankcase with the proper quantity and grade of oil.
4. Fill the coolant system with the proper coolant. Refer to Engine Cooling.

•	Whenever the cooling system is serviced or drained for service procedures, two cooling system sealing pellets, GM P/N 3634621 or equivalent, can be added to the cooling system.

•	Cooling system sealing pellets must be crushed prior to installation. The cooling system sealing pellets can be added to the radiator or the pressurized coolant reservoir.

•	Do not place the cooling system sealing pellets into a non-pressurized coolant recovery reservoir. On these systems, the pellets must be added to the radiator.

•	The sealant pellets may leave a film on the sides of the pressurized and non-pressurized coolant recovery reservoirs. This film is normal.

5. Bar the engine over several times. Feel for any evidence that any of the parts are binding.
6. Start and idle the engine. Listen for unusual noises.
7. Operate the engine at about 1,000 RPM until the engine is at operating temperature.
8. Listen for improperly adjusted valves or sticking valves, and other unusual noises.
9. Check for oil and coolant leaks while the engine is running.
10. Adjust timing. Refer to Engine Controls.