How to Wire an HEI Distributor Cap

by Teeter Allen Morrison
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General Motors developed the High Energy Ignition, also known as the HEI system. The HEI uses a pointless distributor. It was first equipped on some GM cars and trucks beginning in the early seventies, and became standard equipment by the mid-seventies. The HEI distributor eliminated the constant servicing of the old points and condensers found in the earlier standard style distributors. The spark on the HEI system has much greater intensity that older ignition systems. The high intensity spark produces a clean burn in the cylinders and reduces exhaust emissions.

Step 1

Connect the primary wires to the HEI distributor, via a plug that snaps into the distributor cap. There are two wires in the plug: the hot wire and the tachometer wire. If you are updating from an old distributor, splice the old distributor hot wire to the hot wire of the HEI primary plug. Splice the tachometer gauge wire if so equipped, into the tachometer wire on the HEI primary plug.

Step 2

Insert the spark plug wires in the proper order on the distributor cap. The proper order depends on the specific vehicle. The firing order is found in a service manual that matches your specific make, model and year. Sometimes it's stamped on the intake manifold.

Step 3

Locate the distributor's rotor button under the cap and determine its direction. Unplug the primary wire plug from the HEI distributor. Use a flat blade screwdriver to turn the two distributor hold-down screws 180 degrees, and pull the distributor cap away from the distributor. Crank the engine just a little bit to see which direction the rotor button rotates. For instance, a Chevy small block goes clockwise.

Step 4

Consult a service manual to determine where the number one plug wire tower is on the distributor cap. The alternative is to loosen the spark plug on the number one spark plug. Engage the starter until you to hear compression. Continue rotating the engine until the zero mark on the harmonic balancer aligns with the timing tab. The rotor button will now be pointing at number one spark plug tower. Begin with cylinder one, and proceed in the direction the rotor turns, the next tower will be cylinder eight.

Step 5

Insert the number eight spark plug wire next and route it to the corresponding cylinder. For this example we use a Chevy small block firing order, which is: 1, 8, 4, 3, 6, 5, 7 and 2, rotating clockwise. The wires must connect to the corresponding cylinder numbers which are: left bank cylinders (viewing from the driver's seat) 1, 3, 5 and 7; right bank 2, 4, 6 and 8. Low numbers begin in the front of the engine.

Step 6

Plug the distributor primary wire back into the HEI distributor cap and start the engine.

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