Upgrade to HEI
In mid-1974 General Motors offered the Delco-Remy High
Energy Ignition (HEI) as an option for their passenger vehicles, and in 1975
the HEI became standard equipment. Today, many muscle car enthusiasts have
abandoned points and upgraded to some form of electronic ignition, and still
many more would like to, with the few exceptions being those competing with 100
point show-cars. And after all, why not convert? The factory has supplied us
(and ultimately, the salvage yards) with a huge number of electronic ignition
systems, not to mention what is available commercially.
The factory HEI, which is what will be discussed, offers: low-maintenance, great availability of parts, and tunable and reliable performance that can fire-up a high-horsepower engine for street stomping or race track consistency. Any performance-seeker can order an HEI from a number of aftermarket sources, and it will do the same thing as a properly-prepared factory unit from the salvage yard, except it will eat a hole in the owner's wallet.
To upgrade from points to an HEI, begin by obtaining a known HEI, or freshen one up that is in good shape (i.e. no cracks, gear not worn out, no slop from shaft) from the salvage yard; replacing the pickup coil, cap, and rotor as a minimum. The 1974-1/2 units used the same advance weights, springs and stops as the points-type distributor. HEI's do have a part # stamped on the base, but without a number crunching book it will not directly reveal the year or anything else about the unit.
It is critical to understand that the HEI requires 12 volts AT ALL TIMES to work at itís best, and points would burn up with 12 volts at all times, so the factory added either a inline ballast resistor or a resistance type wire that reduces the 12 volts from the battery down to around 9.3 volts to the coil. The points-type distributors do use 12 volts when cranking, however, this is accomplished with a 'bypass wire', located between the starter solenoid (R) terminal and the coil (+) terminal, and is 'hot' only in the ignition switch's 'crank' position and "bypasses" the resistor wire to supply the 12 volts. In other words, on some cars, there will be 2 wires for spark juice, one is 'hot' in the ignition switch "crank" position, the other is 'hot' in the ignition switch "run" position. This was common in the pre-1971 cars, which used an inline ballast resistor with an external voltage regulator.
Starting in 1971, GM introduced another engine-compartment clean-up idea, which was the internally regulated alternator. These were nice, and also eliminated the bulky external regulator. This is significant, because these cars usually did not use an inline ballast resistor, but instead used a resistance wire.
Now, determine which type of wiring harness is in your car. A car that has the ignition switch in the steering wheel column and/or no inline ballast resistor (usually '69 and later), take note of the bypass wire that goes from the (+) post on the coil to the "R" post on the starter solenoid, this wire will be discarded. Verify this with a test light, one 'hot' wire for the ignition switch's 'crank' and 'run' position should be found. If the car is an early Indian, with an inline ballast resistor and/or the ignition switch in the dashboard, it will probably have the 2-wire set up discussed earlier. Verify this with a test light by finding 2 different 'hot' wires for ignition switch 'crank' and 'run' positions.
Now that the 'hot' wire(s) have been located, (which is the hard part, by the way, and the #1 reason why this swap goes sour for some) disconnect the battery, unhook the wires and tape them off. Remove the coil and ballast resistor (if equipped). Set the engine at #1 top dead center, (verified by finger-blown-off-the-sparkplug-hole method or both valves closed at #1 while balancer mark is at zero degrees). Remove the cap from the distributor being replaced, and note location the rotor is pointing. Remove the old distributor. After lubricating the HEI distributor gear and installing a new gasket, install it so the rotor is pointing in the same position as the old one. If the distributor just won't go in that last 1/4", grab a ratchet and 15/16" socket and turn the engine over with the balancer bolt and distributor should fall into place. Install the cap, making sure all three leads (black ground wire is easy to forget) are in the cap receptacle. Install the wire clip from the base into the cap. The HEI will only accept an electronic tachometer, install the tach wire to the (Tach) terminal indicated on the cap.
Now, the HEI needs a connection for 12 volts. Install new 12g wire from the (bat) terminal in the cap through the firewall; and splice into the ignition switch's main feed wire, usually pink in color. If this presents a hassle, any ignition-switched source under the dash will do, just donít use a fuse box accessory connection. If the you have no inline ballast resistor and/or the ignition switch is in the steering column (1 'hot' wire, as verified earlier), this will complete the hook-up, and the bypass wire between the old coil (+) and the starter solenoid (R) can be deleted. If the harness has an inline ballast resistor, and/or the ignition is in the dashboard, the bypass wire will have to be used to supply the HEI with 12 volts when ignition switch is in crank position. In this case, provided the bypass wire is in good condition and is 12g or larger, splice the bypass wire with the new 12g ignition wire and discard the ballast resistor.
Install new HEI wires, gap the plugs around .040"-.045", hook up the vacuum advance to a ported (no vacuum at idle) source of vacuum on the carburetor. Connect the battery, ensure the engine starts and shuts off, and go for a point-less ride!