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ray_mcavoy · 04-10-2018, 05:58 PM

The 7-pin modules are used in applications where the ignition timing is controlled by an ECM. The distributors that use the 7-pin modules do not have any mechanical or vacuum advance mechanisms.

The 4-pin modules are used in distributors that do have mechanical (and usually vacuum) advance. The power feed wire (typically a 12ga pink wire) that plugs into the connector on the cap is the same and can be used to power the replacement distributor. Any remaining connectors (except for maybe a tachometer connection) that used to plug into the old distributor will be unused. And you can probably eliminate whatever ECM and wiring was associated with the old distributor.

04-10-2018, 05:58 PM	#2
ray_mcavoy Registered User Join Date: Nov 2009 Location: Sherman, ME Posts: 2,355	Re: HEI ignition module The 7-pin modules are used in applications where the ignition timing is controlled by an ECM. The distributors that use the 7-pin modules do not have any mechanical or vacuum advance mechanisms. The 4-pin modules are used in distributors that do have mechanical (and usually vacuum) advance. The power feed wire (typically a 12ga pink wire) that plugs into the connector on the cap is the same and can be used to power the replacement distributor. Any remaining connectors (except for maybe a tachometer connection) that used to plug into the old distributor will be unused. And you can probably eliminate whatever ECM and wiring was associated with the old distributor.