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I've been getting around to this conversion for over 5 years and decided to finally do it in 2018 after getting my Quadrajet working well in 2017.  After collecting the HEI pieces from the junkyard, I had to get a few more in order to get started.  To ensure the HEI module put out the hottest spark, I included a couple of relays (run & start) to provide 12V power from the battery.

  • 3 relays & sockets (from Dan Stern Lighting)
  • aluminum bar (for mounting the relays and HEI module
  • rebuilt mechanical fuel pump

After having checked my spark plugs, I see that the G & W terminals on the HEI module are easily bent because of where I mounted the module.  I think it would be wise to use a proper pigtail (like from the SMP LX309) to better support and protect those terminals.  I might need to put a solid cover over the HEI module to protect it while I'm doing any ignition maintenance or just be a lot more careful.

I completed the HEI installation on June 22 and it ran perfectly.  After having tested out various APT (Adjustable Part Throttle) settings of my Quadrajet, I found that I could go from 3¾ turns-out of the APT (pre-HEI) to 0 turns (ie, full metering rod travel).  It doesn't seem to have a lean surge and I can't go any leaner on part-throttle without going up one metering rod size.

While the 1962 to 1974 OEM Champion N14Y slant six spark plugs (gapped to 0.035") work fine, the HEI system's higher voltage allows for wider gaps (0.040"-.045").  I wouldn't go much wider with 7mm spark plug wires as the additional voltage requirement of a larger gap puts unnecessary strain on the ignition system.  GM used a larger distributor cap and 0.045" gap with their HEI engines. The extended tip NGK PN 3459 (ZFR5N) V-Power spark plugs put the spark in a more central location the slant six combustion chamber.

Champion RN14YC NGK PN 3459 (ZFR5N)









If you need to add any circuits from the engine compartment (tachometer, oil pressure, etc) to the passenger compartment, you need to use Packard 56 terminals in the Mopar bulkhead connectors.

Installation Issues

The only issue that I encountered with the HEI Upgrade had nothing to with the HEI system.  Since I had included relays to power my HEI system, I decided to also switch back to using a mechanical fuel pump after having used a Carter P4070 electric fuel pump since 1988.  I had hoped that I could connect the 2 pumps in series and only use the electric pump during starting to ensure that I would not have any vapor lock issues.  However, the P4070 has too much flow restriction when not running and I've had to make some changes to the fuel system.  See Vapor Lock for more information.

Dan Stern's recommended wiring for this system is to connect the start and run circuits and then use that combined signal to operate a battery-supplied relay.  To only operate the fuel pump at start, I needed to keep the Ignition Run and Ignition Start circuits separate.  This required the use of 3 relays:  HEI - Run, HEI - Start, and Fuel Pump - Start.  If you don't have any vapor lock problems and don't need an electric pump, you could get by with a single relay.

Since I no longer have a ballast resistor mounted on my firewall, as a long-term electrical upgrade, I think it would be better add a small fuse block (like the Blue Sea Systems 5045) to power the HEI system and the rest of the car from the alternator.  This would allow me to later upgrade the alternator without having to upgrade the vehicle's wiring harness and the ammeter wouldn't show the HEI and fuel pump loads as battery charging.