Ignition System - HEI-Est (TBI Models): Description

The Delco-Remy High Energy Ignition (HEI) system with Electronic Spark Timing (EST) is controlled by the Computer Command Control (CCC) system. It is designed to provide optimum performance through electronic control of spark timing, air/fuel ratios and idle speed.

The system consists of an Electronic Control Module (ECM), HEI-EST distributor, external ignition coil, and wiring harness. The distributor does not use vacuum or centrifugal advance. See Fig 1 and Fig 2 .

The distributor contains a 7-terminal HEI-EST electronic module, timer core, pole piece, pick-up coil, and a radio noise suppression capacitor.

Fig 1: HEI-EST Distributor With Sealed Connector

Courtesy of GENERAL MOTORS CORP.

The distributor is integrated to the EST system by a 4-wire connector, leading to the Electronic Control Module (ECM). The ECM receives voltage signals from various sensors. A typical system is provided signals from oxygen, engine coolant temperature, throttle position, barometric pressure and manifold absolute pressure sensors.

CAUTION: Few components are interchangeable between HEI-EST and HEI distributors. Always verify correct part is used. Timer core and pole piece have one tooth per cylinder. Similar appearance does not mean correct design or operation.

Fig 2: HEI-EST Distributor Without Sealed Connector

Courtesy of GENERAL MOTORS CORP.