You will need: all the tools necessary to remove the timing belt and engine oil pan, as well as 10, 12, and 14 mm wrenches.
1. Disconnect the wire from the negative terminal of the battery.
2. Drain the oil from the engine oil pan.
3. Remove the timing belt and tension roller.
Warning: After removing the timing belt, do not rotate the camshaft or crankshaft, as the pistons may damage the valves.
4. Remove the camshaft timing pulleys.
5. Remove the timing belt support roller mounting bolt...
6. ...and remove the roller together with its mounting bolt.
7. Remove the two bolts securing the upper rear timing cover.
8. Turn the left one inside out.
9. ...and the right bolts of the lower fastening of the rear cover of the timing drive.
10. Remove the crankshaft toothed pulley.
11. Remove the rear timing cover.
12. After pressing the lock, disconnect the wiring harness connector from the low oil pressure warning light sensor.
13. Remove the engine oil pan (see "Replacing the oil pan seal").
14. Unscrew the two bolts securing the oil receiver to the oil pump and the bolt securing the oil receiver tube to the cylinder block...
Note: Shown with engine removed for clarity.
15. ...and remove the oil receiver.
16. The oil receiver flange is sealed with a rubber ring. A ring that is too compressed, hardened or torn must be replaced, otherwise the oil pump supply may be sharply reduced due to a leaky connection.
Helpful Hint: Every time you remove the oil pan, be sure to wash its mesh with gasoline or kerosene to remove varnish deposits from the oil.
17. Remove the seven bolts securing the oil pump to the engine cylinder block...
18. ...and, prying the pump with two screwdrivers, remove it from the mounting bushings in the cylinder block.
19. If the pump housing gasket remains on the cylinder block, separate it with a sharp tool and remove it.
Helpful Hints: Replace the gasket with a new one each time the oil pump is removed. Install only the original factory-made gasket, as a gasket of a different thickness will cause the pump to malfunction. Also replace the front crankshaft oil seal each time the pump is removed
20. Clean the mating surfaces of the cylinder block and pump housing from any remaining old gasket.
21. Before installation, fill the oil pump cavity with grease to ensure that oil is sucked in from the oil pan when the engine is first started.
22. Install the pump in the reverse order of removal and tighten its mounting bolts evenly crosswise to a torque of 7 N·m (0.7 kgf·m).
23. Install all previously removed parts and fill the engine with oil.
Helpful Hint: When installing a new or reconditioned oil pump, we recommend replacing the oil filter.
The article is reprinted from the website ChevyMan