Installing a Chevy distributor is easy, right? Just line up the rotor, position the housing, and drop it back into theengine. If you've just read that and thought, "Not really," you're not alone. As straightforward as a Chevy V-8 often is to work on, the factory engineers must have taken the day off when it came time to design a distributor for simple installation. The difficulty stems from the fact that the bottom of the distributor gear must precisely engage with the oil pump's drive to allow the distributor to sit flush with the intake manifold. Frequently, though, the oil pump's driveshaft rotates out of engagement position during distributor removal. Add to this the possibility that the engine may have been accidentally bumped over with the distributor removed from the engine. Now there may be two problems: The distributor will not go back in and the engine's timing may be way off.
The cure for this, which involves rotating the oil-pump drive just enough to allow the distributor to be reinstalled and cranking the engine back into position (if needed), often takes some creativity and some patience. Fortunately, none of this is a big problem. With a few easy steps you can have your distributor back in and your engine timed in almost as much time as it takes to throw a few wrenches and yell some expletives. You'll need a few simple tools to do this, but in a short order your engine can be running properly-just don't forget to make sure all your plug wires are properly positioned on the distributor cap. So follow along as we take a trip to go back in time.
Before removing or loosening...
Before removing or loosening the distributor it's a good idea to mark the position of the housing. This will make it easier to reposition the distributor close to the original timing setting during reinstallation.
After removing the distributor...
After removing the distributor cap, crank the engine until the timing mark rests at an easy-to-note position. This is typically straight ahead or rearward. Also pay particular attention to the location of the vacuum advance unit and mark its direction with a small piece of masking tape and marker on the passenger-side valve cover. Next, remove the distributor clamp, then rotate and pull the distributor up and out.
To reinstall the distributor,...
To reinstall the distributor, the top of the oil-pump driveshaft slot (located at the bottom of the distributor hole inside of the engine) must line up with and accept the tang at the bottom of the distributor. This shot (taken inside the engine) shows the top of the oil-pump driveshaft. If this shaft turns during removal, if the engine is cranked over with the distributor out, or if the engine is being started for the first time, this oil-pump drive will need to be rotated into proper position.
The bottom of the distributor...
The bottom of the distributor gear has an inner tang that must mesh with the slot in the top of the oil-pump drive. Additionally, the distributor's lower gear must simultaneously engage with the gear at the rear of the camshaft.
If you simply want to clock...
If you simply want to clock the oil-pump drive, you can use a large screwdriver to move the drive. Be sure not to use a small screwdriver, because it will never reach inside the engine and you may accidentally drop it into the intake manifold.