If there is a standard in the world for a stand-alone electronic ignition distributor for GM engines, it has to be the High Energy Ignition or HEI distributor. This large cap distributor first appeared on small block Chevy engines in the middle of 1974 and remained well through the '90s in various other forms. The advantage of the HEI distributor is its longer ignition coil dwell time that can deliver greater ignition current to the spark plugs at high rpm. Add to this its integrated ignition coil in the distributor cap, and the HEI is the go-to distributor for basic GM street engines and an easy replacement for buggy-whip-era points distributors. We will concentrate on the early four-pin-style HEI distributor and a few of the performance parts that can transform an old sparker into an electrifying ignition system. For the budget car crafter, the trick is to start with a good used HEI. When evaluating old HEI distributors, the first place to look is under the rotor. A common HEI malady is for stray voltage to burn through the rotor and to ground through the small mechanical advance weight pivots. The evidence is a rusty-looking iron oxide film on the inside of the rotor and distributor cap. This is clear indication that the posts will be badly worn. This is often followed with a frozen mechanical advance mechanism. If you find a distributor like this, its best to just keep looking for one in better condition. The best rebuild procedure is to completely disassemble the distributor by unbolting the vacuum advance, module, removing the drift pin and gear and yanking the shaft. This way, the distributor body can be thoroughly cleaned, lubed, and reassembled. Mr Gasket sells an inexpensive distributor shim kit that you can use to reduce the overall endplay down to around 0.015 inch. Most stock HEI's have as much as 0.060 inch or more endplay. The excess clearance allows the drive gear to climb the cam gear and retard the ignition timing. Reducing the endplay eliminates this problem. When buying replacement parts, choose a distributor cap with brass inserts. Less expensive caps use aluminum spark plug wire connectors that corrode and increase resistance. This greater resistance is often the cause of cross-sparking inside the distributor cap. Lube the shaft lightly and then reassemble the mechanical advance mechanism. Another way to eliminate those stray HEI sparks from finding a ground path is to use the plastic rotor screws from Performance Distributors. Finally, always connect any HEI to a switched 12-volt source that does not use a resistance circuit. This will allow it to operate at its maximum potential. One way to do this is by using a high-quality relay to offer switched power to the distributor. With these tricks and a few more outlined in the photos, you can build your own high performance HEI distributor without flattening your wallet. Parts List Description PN Source Price MSD cap & rotor 8416 Summit Racing 26.95 MSD HEI module 83647 Summit Racing 95.95 MSD ultimate kit 8501 Summit Racing 202.95 Accel cap & rotor 8123 Summit Racing 20.95 Accel HEI module 35361 Summit Racing 43.95 Accel Ult. module 35373 Summit Racing 145.95 Accel Brute coil 140005 Summit Racing 63.95 Summit module 850100 Summit Racing 39.95 Summit HEI kit 850014 Summit Racing 29.95 DUI module 000222 Summit Racing 49.00 DUI cap & rotor kit 12000BK Summit Racing 29.99 DUI plastic screws 91012111 Speedway Motors 0.99 ea. Pertronix module D2000 Summit Racing 42.95 Pertronix Flame kit D8001 Summit Racing 124.95 Delphi module OS10071 RockAuto 19.48 Airtex dist. cap 5D1058A RockAuto 14.29 Mr. Gasket dist. shim 2820 Summit Racing 7.95 Heat-sink material 15659 Summit Racing 2.99 Heat-sink material 276-1372 Radio Shack 3.49 Rather than spend $150 or more on a trick aftermarket distributor, you can build your own high-perf HEI for a lot less that will perform just as well. Rather than spend $150 or more on a trick aftermarket distributor, you can build your own high-perf HEI for a lot less that will perform just as well. This is what happens if you omit that rubber insulator underneath the coil when replacing a distributor cap. Amazingly, the engine was still running before this cap was replaced. This is what happens if you omit that rubber insulator underneath the coil when replacing For street engines, more spark current can easily be had with a high-performance module. Accel, MSD, Pertronix, Performance Distributors, and many others offer modules that can enhance performance. For best performance, these modules should be paired with a matching coil. For street engines, more spark current can easily be had with a high-performance module. A All HEI modules come with a small vial of heat-sink material that should be spread between the module and the distributor body. A thin covering is all that is needed. This material improves heat conductivity between the module and the distributor body. You can also buy this material separately from Radio Shack. All HEI modules come with a small vial of heat-sink material that should be spread between By Jeff Smith Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!