How to wire mid-1970s through mid-1980s ignition system with a GM ignition module

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Jul 9, 2009 | 12:42 PM

GMdude

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How to wire mid-1970s through mid-1980s ignition system with a GM ignition module

GM HEI module creates a hotter spark and doesn't use a ballast resistor. this is the way I do it:

Get a standard Chrysler electronic ignition distributor (wrecking yard, auto show, etc.). Get a good quality HEI module such as NAPA Echlin TP-45, ACDelco D-1906, or Standard-Bluestreak LX-301. Fetch a piece of aluminum 1/4" thick by about 2" by about 3-1/2" Drill two holes in it to match the HEI module's mounting holes Heat sink compound comes with every new HEI module. Squirt some onto your mount plate, put the HEI module on the plate, and secure the plate and module to the inner fender. Strictly speaking, this aluminum mounting plate is optional. It helps assure temperature and mount stability of the module. the mod can be done by just bolting the module to the inner fender with acceptable results, but in the long term, the aluminum is probably worth the trouble.
Remove ballast resistor. Discard or keep in glove compartment to rescue fellow Mopar owner. Take the two connectors that used to connect to the resistor, and connect them to each other instead

All you have to do is make sure you use the correct-size female spade terminals (three of the four terminals on the module are one size, the fourth is 3/16".)
Holding the HEI module with its convex side down or toward you, the upper left is terminal B, battery; lower left is C, trigger; and the two on the right are for the distributor pickup coil. Which pickup coil wire goes to which module terminal is determined by trial and error: If engine is difficult to start or runs poorly after installation, you swap these two wires.
So, two wires from an ordinary Mopar electronic distributor go to two RH terminals, upper left B gets connected to coil (+) primary so that it gets +12V from ignition switch (no ballast resistor in between!), and C goes to coil (-) primary. The only other thing that needs to be assured is a proper module ground, but it's very difficult not to have this!

7. Add a relay:

If the ignition module (any ignition module) is starved for power, it'll work unreliably and it'll die prematurely. The module needs to see full line voltage, and the wiring in most of our cars isn't up to that task after all these years. So, when setting up your module wiring, it's best to install a relay that'll provide full line voltage to the module via the coil + terminal. Use a good brand of relay (Bosch/Tyco, Omron, and Hella are three good picks). You need an ordinary 4-prong normally-open ("SPST") relay. The prongs will be labelled #30, #85, #86, and #87.
#30 is your power input. Connect this via a 14ga wire to a good, solid source of line voltage. Good options for where to pick up this power feed include the battery positive terminal, alternator B+ terminal, large terminal on the starter relay, large terminal on the starter. Put a fuseholder in this wire as close as possible to your power takeoff point. You'll want a 15A fuse, and you'll want to carry spares.
#85 is your trigger ground. Run a 16ga wire from this one to any decent ground.
#86 is your trigger feed. This one needs a 16ga wire that's live when (and only when) the ignition is switched on.
#87 is your power output. Connect this via a 14ga wire to the coil + and then from there to the module's power terminal.

8. Assure is a proper module ground. It's rather difficult not to have this just by installing the module, but I like to run a ground wire to one of the module mounting bolts just to be sure.
9. Use either a standalone late-model spool-type coil (GM or Mopar) or spend the $35 on an MSD Blaster, which fits the stock can-type coil bracket. At the very least use a coil such as the Standard-BlueStreak #UC16 or NAPA Echlin #IC27. It's best, though, to use a coil intended for use with a high energy ignition system. If you'd like to mount the module off by itself somewhere, then a good coil option is the stock external-mount GM HEI coil used on 1975-84 GM cars (mostly with 4-cylinder engines). The coil is a Standard/BlueStreak DR35.

One tidy option is to use the combination HEI coil/module/mounting bracket. This way you take advantage of GM's own work, and just bolt this combination module/coil/heat sink unit to the inner fender. This assembly is used in just about all gasoline-fired GM pickups and RWD SUVs from 1996 to at least 2000. It includes a sturdy mounting bracket, heat sink for the module, E-core ignition coil...all in one. Wherever you are, you can probably pull these out of wrecking yards all day long for very little money, and you can grab the watertight connectors for the coil and module while you're there. However, this coil has a male (spark plug type) secondary terminal rather than the female type on our original coils, so you'd need to get an appropriate coil-to-distributor-cap cable.
11. Open plug gaps from 0.035" to 0.045" (improved starting, idling, driveability, mileage) i'm going to try even wider

12. The price of the electronic ignition's performance is paying more careful attention to the condition of your distributor cap, rotor and spark plug wires. You can also change them out. The trick piece in this department is a NAPA Echlin long-tip rotor # MO-3000, which has a brass contact 0.060” longer than stock. This means less arcing inside the distributor, which means less burn wear on the cap and rotor contacts and less ignition noise in your radio. Be careful about Echlin or Accel distributor caps, though; many of them are ground off-centre and can cause carnage when the rotor—especially the longer special one—hits one of the improperly-ground, too-big cap contacts. The safer alternative is a Standard-Bluestreak CH-410X. Get Magnecor wires and you won't have to think about your spark plug cables again for a very long time.
13. Drive and enjoy.

this works very well and the cost is about $35.00 ..

Jul 9, 2009 | 02:38 PM

scotts74birds

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From: Michigan: The First Line of Defense From The Canadians!

Interesting, might it be easier to snip the module harness from a junkyard car? = pennies

Jul 9, 2009 | 03:23 PM

GMdude

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it's really not as hard as it sounds .. the gm mod was like 20 bucks .. the relay was like 5 bucks and then just rolls of wire and spade connectors.. really if you don't want to you don't have to use the relay ... i like to use one so that i know that i have good connections and wire ... you can just use the wire that goes from the resistor to the coil .. off the top of my head ..thinking it the brown one ??? only thing you have to watch is the wiring from the dizzy to the gm mod ..if car no start .. switch the two wires .... if i knew how to post pics in here i would show you my set up .. it's not that neat.. could be better .. but it works

Jul 9, 2009 | 03:26 PM

GMdude

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and yes mr bird .. sniping a harness from a parts yard is a good idea ,, i just didn't want to make that trip .. .. how much could one be from the parts store ,,, few dollars ..