How to Change an HEI Distributor

HEI stands for High Energy Ignition, and it is a certain type of distributor used on automotive vehicles. HEI distributors, rather than having points which open and close to send spark through the cap and wires, use an electromagnetic signal inside the distributor to send a voltage pulse to fire the cylinders. Changing an HEI distributor can be accomplished easily if the repair person follows a few simple steps, which requires aligning the new distributor shaft in the exact position the old one was removed.

Instructions

1

Place the vehicle in park or neutral, depending upon the transmission type. Set the emergency brake. Raise the hood and use a socket and wrench to remove the negative battery cable. Refer to you owner's service manual for the location of your number 1 cylinder on your engine. For example, on Chevy engines, the number 1 cylinder is located on the right bank at the front of the engine as you look at the engine from the radiator side. Gently remove the number 1 plug wire from the spark plug with spark plug wire pliers.

2

Locate the harmonic balancer (crankshaft pulley) at the front bottom part of the engine. Clean the outside edges of the harmonic balancer and the small metal timing tab with a rag. You will need to see the timing notch on the balancer and the TDC (top dead center) or "0" timing mark on the tab. Use a flashlight to get a clear view of the notch and tab. Check your service manual to identify it.

3

Use a socket to remove the number 1 spark plug. Place a thin screwdriver in the spark plug hole, shank first. Connect a large socket and breaker bar to the center nut on the harmonic balancer. Turn the breaker bar until you see the screwdriver raise up from the number one spark plug hole and top out. See if the notch on the harmonic balancer has aligned (or is close) with the TDC or "0" mark on the timing tab. This means the piston is at TDC.

4

Follow the number 1 spark plug wire up to the distributor cap and note where it connects to the cap nipple. Take a scratch awl and mark a line on the distributor body case directly below the nipple -- this will show you the proper cap orientation. Use a screwdriver to remove the distributor cap, or pop the spring clips that hold the cap to the distributor body. Push the cap aside but do not remove the wires. Look at the position of the rotor contact; it should be pointing at the number one spark plug position, which is the mark you scratched on the distributor body.

5

Turn the harmonic balancer with the breaker bar if the rotor faces the other side of the distributor. Turn the balancer 180 degrees to point the rotor at the number 1 spark plug position. The screwdriver should rise again while you do this. Now you have the proper TDC. Release the pressure snaps that hold the HEI wiring jack to the side of the distributor, and pull it away. Use a socket, extension and wrench to loosen and remove the distributor base clamp bolt.

6

Take the distributor body in one hand and the rotor in the other hand and pull the distributor straight up and out of the engine. Twist the rotor slightly to aid in removal, if you need to. Place the new distributor down into the mounting hole, using one hand to maneuver the distributor body and the other hand to turn the rotor contact so it lines up with the small scratch mark you made on the distributor body case. Push the distributor down until it seats flush with the engine. Turn the rotor slightly back and forth to get the distributor gear to engage the camshaft gear.

7

Have an assistant turn the harmonic balancer with the breaker bar slightly back and forth, if the distributor does not seat fully into the engine. The distributor gear many mesh, but you need to align the oil pump slot and key on the bottom of the distributor shaft for it to completely seat. Once the distributor drops down all the way, check to see if the rotor contact aligns with the scratch mark. It should align. Replace the distributor base clamp bolt and tighten it with the extension, socket and wrench.

8

Snap the HEI wiring jack back into its socket. Place the distributor cap back onto the distributor and secure the hold-down screws with a screwdriver, or snap the clips into position. Remove the screwdriver from the number 1 spark plug hole and replace the spark plug. Tighten the spark plug with a socket and wrench. Push the spark plug wire onto the spark plug. Use a socket and wrench to reconnect the negative battery cable.