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The HEI system works best with the e-core coils because e-core transformer coils operate at higher efficiencies due to less leakage inductance and can nearly double the effective spark energy of canister coils.  See HEI Coil- E-core vs canister:

An E-core coil has an improved magnetic circuit path. The canister coil magnetic path is a rod, so it is like a bar magnet. The E-core wraps around and has a small air gap, so there is less leakage inductance. The E is shape of core, the windings go on the center bar, that is slightly shorter than ends. An I bar closes the ends, the air gap is in the center. The windings, often on a bobbin, are shorter, and fewer turns, less resistance, so less copper losses. So the E-core is more efficient, a higher percentage of energy gets to plug.

Once the coil has become saturated, additional current flow in fixed dwell ignition systems only generates unnecessary heat but provides no gain in additional spark energy. 

HEI e-Core Coil

Since we're not likely using the large cap HEI distributors that have the coil mounted in the distributor cap, we need to get a remote-mount e-core coil. Although pre-1986 junkyard HEI parts would also work, there are effectively 3 e-core options to choose from:

  • AC Delco D577 - 1996-2007 GM with the 3-pin plug & HV internal pin
  • AC Delco D503A - 1986-1995 GM with the 4-pin plug & HV external stud
  • Motorcraft DG470 - 1983- 1997 Ford and Mazda electronic ignition


HEI e-Core Pigtail

The old canister coils use ring connectors to connect to the coil.  The best way to connect to the new e-core coil is with its matching pigtail.



HEI e-Core Coil Wire

If you're using an e-core coil, the coil wire could potentially be reused from a junkyard system but spark plug wires can be too old to be reused.  It would be better to source a new coil wire or modify your existing coil wire with the correct e-core coil terminal and boot.


HEI e-Core Coil Bracket

If you're using an e-core coil, you need to mount the coil somewhere and the most obvious place would be in the old canister coil's location.  We have a bracket that allows the coil to be oriented upwards or sideways.  You can order this from our e-store by visiting HEI E-Core Coil Bracket or clicking on the bracket photo below.




AC Delco D577 System

AC Delco D577 Coil 3-pin Pigtail Coil Wire
(Internal Pin)
Reuse the coil terminal and boot from your parts car.


AC Delco D503A System

AC Delco Coil D503A Coil 2-pin Pigtail Set Coil Wire
Standard Motor Products S562 (Gray)
Standard Motor Products S563 (Black)
Standard Motor Products PN 814CA


Motorcraft DG470 System

Motorcraft DG470 Coil 2-pin Pigtail Coil Wire
Standard Motor Products PN S539
Standard Motor Products PN 814CA