Pontiac HEI System - High Energy Inspection - Low Buck Tech

Pirated from another project, it's painfully obvious what a lack of lower bushing lubrication can do to a mainshaft. Combine this scoring with the severely worn lower bushing, and the result is an unusable HEI. Though spray-welding or hard-chroming might salvage a mainshaft and a new lower bushing could be installed into the housing, the expense of both repairs may not offset the cost of purchasing another unit if numbers-matching isn't a concern.

If after removing the gear, the mainshaft doesn't want to slide out easily, don't force it! Damage to the shaft or bushings could result. Instead, place the unit in a vice and spray a liberal amount of carburetor cleaner (or equivalent) down the lubrication veins, allowing time for it to penetrate the varnish. It may take several applications of cleaner and several minutes of gentle twisting to fully extract. Once the mainshaft is out, be sure that the veins are free from build-up.

The C-clip retaining the pick-up coil assembly fits in a groove machined into the outer diameter of the upper bushing. Remove the pick-up coil to access the upper bushing's grease well.

Test the resistance of the pick-up coil to determine its condition. Factory specs allow for an ohm reading between 500 and 1,500, but we've found the best results when using new and used units that measure between 780 and 820. Closely inspect the condition of the wires where they enter the assembly-they can break internally without much external indication.

Some HEIs have a felt washer on top of the grease well seal. Use a sharp awl to rotate and remove the plastic seal under it that covers the grease well. GM filled it with a lubricant that's solid at lower temperatures and liquefies at higher temperatures, allowing it to permeate the upper bushing and lubricate the mainshaft. What little is left of it today oftentimes offers no benefit. Thoroughly clean the entire housing and fill the well with silicone-based, low-temperature wheel-bearing grease. A drop of engine oil on the felt washer (if so equipped) during reassembly is all that's needed. Its purpose is to lubricate the pick-up coil as it rotates with the vacuum advance.

Before inserting the mainshaft and timer core into the housing, polish the shaft with 600- to 800-grit sandpaper to remove any burrs. Then, fill the groove in the mainshaft with bearing grease and lightly coat the mainshaft with engine oil. Once the unit is back together, lubricate the pivot points of the centrifugal advance to ensure linear operation, and treat the housing to a new Felpro gasket (No. 11497).

You don't need a distributor-testing machine to accurately calibrate your HEI's centrifugal and vacuum advance curves for maximum performance. Bob Davis of D&D Manufacturing in Memphis, Tennessee offers complete mail-order HEI curve kits, like the one shown here. Simply provide him with your combination's specifics and about $50, and in return you'll receive a high-quality kit calibrated to match your engine's needs.

On April 9, 1974, Pontiac sent Sales Information Bulletin No. 74-12 to its dealer's sales staffs announcing that HEI would become the standard ignition system on all 400 and 455ci engines (except the SD-455) on May 1. A similar bulletin containing additional detail was sent to service departments.