Electronic Ignition Systems
The Delco-Remy division of General Motors was responsible for a number of innovative electronic designs, and one of those was a breakerless ignition system. Used by Pontiac in the '60s and marketed as its Transistorized Ignition system, it was fairly complex and used an electronic module to trigger coil firing instead of conventional breaker points. While very reliable in operation, the system ultimately gave way to the Unitized Ignition system released towards the end of the '71 model year.
As we learned in "Unitized Ignition, Anyone?" (HPP, Mar., '04), the Unitized Ignition system was completely self-contained and required only a single 12-volt power lead for normal operation. While not necessarily offering any additional spark intensity, Unitized was touted in sales literature as requiring no periodic maintenance, improving wet-weather performance, and providing consistent spark output at all engine speeds. Unitized seemed to be a popular option and was available on most 400 and 455 4-barrel applications through midyear 1974.
On April 4, 1974, however, Pontiac issued to its dealers' service department Technical Service Bulletin 74-I-30, informing them that in early May, a new High Energy Ignition system would replace both the conventional and/or Unitized systems as the standard ignition on nearly all 400 and 455ci engines.
The bulletin went on to say that HEI offered extended spark plug life, and that its increased spark intensity was beneficial when igniting lean mixtures and those diluted by EGR. It revealed a plethora of revised engine codes for the affected applications, as well as a detailed troubleshooting chart and servicing procedures. It also boasted that the HEI contained just nine electrical connections-eight of which are for spark plug wires
Pontiac used HEI exclusively on all its V-8 engines from 1975 forward, and the design remained unchanged throughout much of that time. It was, however, revised slightly when Computer Command Control (CCC) was introduced during the '80 model year. In these instances, the mechanical and vacuum advance components were replaced by electronics that controlled spark advance entirely. As the number of Pontiac V-8 engines with CCC increased in 1981, the division no longer used a conventional HEI.
Don't let the looks of this...
Don't let the looks of this HEI scare you! We found it in a '76 LeMans at our local salvage yard. Upon removing it from the engine and giving it a quick physical inspection, we determined that it was worth purchasing. The complete unit, including cap and coil, was ours for $30. After complete disassembly, thorough degreasing and replacing the centrifugal and vacuum advance components, the unit operates flawlessly.
To quickly gauge the condition...
To quickly gauge the condition of the mainshaft and lower bushing before leaving the salvage yard or handing over money at a swap meet, simply grab the housing with one hand and the driven gear with the other, and apply lateral force. Then spin the gear to another position and test again. There shouldn't be any side-to-side clearance in any direction. The gear should also rotate easily-binding might suggest varnish build-up on the mainshaft, possibly hiding the distributor's real condition.
Remove the roll pin securing...
Remove the roll pin securing the driven gear onto the main shaft for complete disassembly. The shim is used to limit endplay (we routinely set ours to around 0.020-inch). More is acceptable, but significantly less could prevent proper lubrication of the lower bushing, or possibly bind the centrifugal advance or oil pump as the aluminum housing expands. Also, be sure to align the machined "dot" on its side with the rotor tip when reinstalling the gear. According to vintage Delco literature, its purpose is to properly phase the distributor during installation into an engine.
Selecting An HEI
Finding a used Pontiac HEI isn't a difficult task. What can be difficult, however, is locating one in good, reusable condition. While replacements for electronic components are usually just a trip to the local parts store away, other commonly worn or damaged pieces, like the internal bushings and mainshaft, are very difficult to replace.
Of the two bushings that support the mainshaft, the lower bushing is most commonly worn. While the upper bushing is surrounded by a grease-filled well, the lower bushing relies on engine oil mist migrating upward from the camshaft area for lubrication. Sludge deposits commonly found in engines lacking routine oil maintenance can clog the distributor housing's internal passageways, limiting lubrication. This can lead to scoring of the mainshaft and severe elongation of the bushing during normal engine operation. See the enclosed photos and captions to learn more about how to choose a rebuildable HEI.