1. Preparation:
* Gather Tools: You'll need a socket set (including a wrench to match your distributor hold-down bolt), a distributor wrench (if the distributor has a clamp), a timing light, a timing pointer (if your engine doesn't already have one), possibly a breaker bar, pliers, and possibly some dielectric grease.
* Disconnect Battery: This is crucial to prevent electrical shorts and damage. Disconnect the negative (-) terminal first.
* Remove Old Distributor:
* Loosen the distributor hold-down clamp.
* Note the distributor's position relative to the engine block. Take a picture or make a mark if you are unsure. This is extremely important for proper timing.
* Carefully remove the distributor. It may be slightly stiff.
* Disconnect the wires from the old distributor. Take a picture or label them carefully to ensure correct reconnection. The wires are usually for the ignition coil, and the pickup coil which is sometimes combined.
2. Installing the HEI Distributor:
* Install the HEI Distributor: Carefully align the distributor with the engine block, matching its position to the old distributor's location (this is where your mark or photo becomes vital!). The distributor shaft should align with the oil pump drive. Some distributors may have a small alignment notch.
* Install and tighten the hold-down clamp: Secure the distributor firmly in place, following the appropriate torque specifications if possible. You might need the breaker bar.
* Reconnect Wires: Carefully reconnect the wires to their respective terminals on the HEI distributor. Reference your picture or labels if necessary.
* Connect the Coil (If necessary): HEI distributors have the ignition coil built in. Older engines may require connecting the coil.
3. Setting the Initial Timing:
* Install Timing Light: Connect the timing light according to the manufacturer's instructions. You'll usually attach one clip to the battery's positive (+) terminal, and the other to the ignition coil's positive (+) terminal.
* Connect the timing light pickup: Aim the timing light's pickup at the timing pointer and crank pulley.
* Start the Engine: Slowly crank the engine over and observe the timing mark on the harmonic balancer (crank pulley) through the timing light's strobe.
* Adjust the Distributor: The timing mark on the harmonic balancer should align with the 0° mark on the timing pointer (or the manufacturer's recommended timing setting, typically found in your vehicle's repair manual or stamped on a tag on the engine). If it's not aligned, carefully rotate the distributor slightly to adjust the timing. This often requires using a distributor wrench for smaller adjustments. ONLY adjust the distributor slightly. Don't force it.
* Repeat steps for final timing: Once close, double check that the distributor clamp is tight. Reconnect the negative (-) battery cable and restart the engine to recheck the timing.
4. Post-Installation Check:
* Test Drive: Take the vehicle for a test drive to ensure proper engine operation. Listen for any unusual sounds. Check for strong acceleration. If the engine runs poorly, the distributor may need to be slightly readjusted. If that does not fix the issue, recheck all connections.
* Rev Limiter (If Applicable): Some HEI distributors have built-in rev limiters. Verify that the engine does not exceed the manufacturer's recommended RPM.
Important Considerations:
* Distributor Type: HEI distributors come in different variations. Ensure you purchase the correct one for your specific application (e.g., small block Chevy 350). Many distributors specify a particular model year range.
* Engine Year: Older models may have different timing settings. Consult a workshop manual for specific timing requirements for your year and model.
* Vacuum Advance: Some HEI distributors incorporate a vacuum advance mechanism. Ensure this is correctly connected and functioning.
* Professional Help: If you're uncomfortable performing this task yourself, consult a qualified mechanic. Incorrect installation can lead to engine damage.
This guide provides general instructions. Always consult a repair manual specific to your vehicle's year and model for detailed instructions and torque specifications. Remember safety first—always disconnect the battery before working on the ignition system.
