Guest Blogger-Street Rod 101
How should the lubrication system on a GM small block be primed when starting an engine after a long storage period?
When an engine is in storage for a long period of time, it may be necessary to prime to the lubrication system. This is also true after rebuilding an engine. This is done to make sure there is sufficient lubricating oil on the bearing surfaces when you first start to crank the engine. Over time, when an engine is not run, the amount of oil on the main and connecting rod bearings continues to be reduced. Most of the oil on the surface of the bearings and crankshaft is drained back to the oil pan. It usually takes months of storage to do this, but the longer the storage period, the less oil that remains between the bearings and the crankshaft. If an engine is started without sufficient oil on the bearings, there may be enough friction produced to spin the bearing. If this is the case, it would damage the bearings to the point they need replacement.
To get sufficient oil to the bearings before cranking the engine, the oil pump must be rotated . This is called priming the lubrication system. On this engine, the oil pump is driven by the distributor shaft, which is driven by the camshaft. To do this, technicians often use an oil pump primer shaft. These can be purchased at most automotive parts stores. The shaft is connected to a 3/8 drill. After the existing distributor has been removed, the shaft is placed down through the intake manifold and onto the oil pump drive shaft. As the drill is turned, the oil pump produces pressure and the lubrication system is primed.
Another way to prime the oil system is to make your own primer tool. First, get a used distributor and cut the top off so a 3/8 inch drill chuck can be attached on the top end of the distributor shaft. Then, after the existing distributor has been removed, lower your primer tool into the engine to the same position of the existing distributor. When the drill is attached and turned, the primer tool will turn the oil pump to prime the lubrication system. The photo below shows an example of the primer tool made from an old distributor. The left side attached to the oil pump drive shaft. The drill is placed on the right side. The two extended surfaces on the middle left, help guide oil into the main oil galley and lifters when the pump is turned.
1. Remove all wires from the existing distributor. It may not be necessary
to remove the plug wires.
2. Remove the distributor cap and observe the exact location of the distributor rotor.
In this case, it is pointing directly to the back of the vehicle (or the firewall).
See photo below.
4. To keep the ignition timing the same when your done, mark the exact position
of the distributor in reference to the intake manifold. See the photo below.
There is a mark from the distributor housing to the intake manifold.
Now remove the bolt and bracket holding the distributor in place.
block. As you are pulling it out, note that the distributor cap will rotate slightly
to the left. This is because the gear that drives the distributor shaft is
a helical gear. This means the gear teeth are at an angle which causes the
shaft to rotate slightly as it is pulled out.
6. With a flashlight, look down into the distributor hole and identify the position
of the oil pump drive shaft. It should look like the end of a large flat head screw.
Note this position.
7. Attached the 3/8 inch drill to the primer tool shaft as shown in the photo below.
pump drive shaft slot. When engaged, the primer tool housing should fit flush
to the intake manifold. If not, the primer tool is not engaged with the oil
pump drive shaft slot. The photo below shows the bottom of the primer tool
and the part that must match up with the oil pump drive shaft slot.
for about one minute. This should be enough time to get oil to all of the
bearings and lifters.
10. Remove the primer tool. Using a long screwdriver turn the oil pump drive shaft
to its original position noted in step 6, when the existing distributor was removed.
11. Reinsert the original distributor housing back into the engine. As the
distributor is being inserted, it must match up to the position of the oil pump
drive shaft mentioned in step 6. If not, you may need to take the long screw
driver and reposition the oil pump drive shaft to the correct position. Also,
when fully inserted, the distributor rotor MUST point to its original position,
identified in step 2.
12. Attach the hold down bracket to the distributor and gently snug down the bolt.
Reposition the distributor housing to the exact position as identified in step 4.
13. Tighten down the distributor housing hold down bolt and bracket making sure
the housing is in the correct position. Attach all wires and the vacuum advance
13. Start engine and check to make sure the timing is set to manufacturer’s
specifications. It should be very close if all step were followed correctly.