Retrofitting breaker point ignition


It seems I have some kind of “EMP aura” around me, since (particulary car) electronics tend to die over time when I’m in the neighbourhood. That’s why I like old cars. Or have the wife driving the newer ones.


My '73 Chevy C-20 454 was equipped with an electronic distributor by the former owner. This morning it went wrong. Luckily only half a mile from home the engine stalled. No spark, despite 12 volt at the distributor. There you go with a tri-fuel powered car…

Knowing for sure that the electronics would fail one day, I already gathered a used breaker point distributor, new spark plug wires, a coil and had these parts stocked up. Still, two questions remain:

  1. Which position is best for the ignition coil? The electronic one has it integrated in the distributor cap, so I can’t see where it was before.
  2. I’m not sure whether the resistance wire between coil and ignition switch is still present. How can I recognize this wire and on which end is it mounted? If it isn’t there anymore, can I use a common HD resistor and what rating?

I know; electronic ignition gives the best spark. But I prefer a poor spart above no spark…



Good to hear from you, and glad the truck is still going. (well until today!) Curious to hear how it’s doing after a year on the road.

It is the nature of electronics to fail, but automotive stuff is fairly reliable. I guess it’s no match for your electric personality! :slight_smile:

I don’t think it matters where you mount the coil. I’ve seen them sideways and vertical. Somewhere on the firewall should be fine, just make sure all the wiring reaches. A quick image search didn’t show the factory placement, but you may find it in a shop manual. But again, I don’t think it matters.

Sorry I don’t know about your second question, I’ll let a real engine guy answer that.

Good Morning Dutch John
Mount the ignition coil somewhere on the intake manifold as determined by the length of the coil wire. Coil body needs a reasonably good direct to the engine ground path. Mount either horizontal or tower post up.
The manual sent to you will give the color of the IG switch to coil wire. Attached to the coil. Then key on voltage checked against this coil load at the coil primary terminal will tell you if this is a voltage dropping resistance wire or a standard wire. Standard wire with full battery voltage and yes you will want the external inline running dropping resistor added. For full voltage cranking to start to the coil down on the starter mounted solenoid switch is a small “R” for relay marked terminal opposite the currently attached “S” or “IG” terminal. Wire will have to ran from here to the coil “Batt” terminal. The key ignition switch in cranking position will open circut the coil feed line and the coil is then supposed to be fed full cranking battery voltage up from the activated starter soleniod. Do make sure that this circut IS feeding starter switched full cranking voltage. Later starter solenoids for electronic ignition do not have this extra R terminal. Those that do can have a worn/damaged internal brass finger that soleniod activated connects to the bridging disc with then battery voltage. Symptom of loss of this circut is will NOT start while cranking but fires up on key released from cranking to spring back to run position.

Maybe either your “magnetic” personality or reluctance for IC chip dependencies, eh? My mother would kill all quartz electric watches and stop windup watches! She could only wear push to read LED watches.

Steve Unruh

DJ Hello
If you must replace your HEI distributor with a points style, Steve U’s info is correct. I feel that changing the HEI out for a points style distributor will not be in your best interest in the long run. Spark plugs will become more of an issue, they will only last half as long at best. The big problem with the HEI were the wires from the pickup coil to the the solid state module. check these wires for breaks.

Best of luck

The only problem I’ve ever had from an HEI is one module go bad. Very reliable and one of the best things to come from gm in the 70’s.

Don’t know how familiar you are with Chevys but if the points distributor you got was used check the cam lobes for wear, mechanical advance bushings for wear, and that the vacuum advance is free and working. Stay with the best point you can get. Standard brand “Blue Streak” has worked well for me.

Not going to try and talk you out of swapping but I think your going the wrong direction. If you decide to stick with HEI I’ll send you a module. Think I may be able to come up with the wiring also.


DJ, I’d stick with the HEI. I think they were 50,000 volts versus 12,000 volts. That was quite an improvement over point ignition. Check the pickup coil connections before you jump to any conclusions. I have one out in the shed and can look at it in the next day or so. I can’t recall if the vacuum advance made the wires flex on the pickup coil or not. Last car I had was a 79 chevy with that system and I junked that around 1989 but I still have a spare distributor in the shed under a pile of junk … Mike L

GM points distributor -------- extremely bad plan.

DJ, Can you easily buy replacement parts in your country ?? I think the stuff is still hanging on the walls in some of the stores around here. Let me know what you might need if you can’t get it there. It will probably take a couple of weeks to pick it up and also get it to you but I’m game. On the phone I’m usually at USA of course 608-623-3000 … Mike

“I know; electronic ignition gives the best spark. But I prefer a poor spark above no spark…”

I’m with DJ on this one.

Mine failed a couple weeks back, and it came home a towbar… While I watched many older engines purring away on their old style ignition and induction systems.
I will be gathering the necessary parts to convert to points in the event of another failure. Electronics are awesome when they work… and an absolute Pain in the butt when they fail in a farmers field 70 KM from home.
My 2 cents

Thanks for the many replies. The HEI shines like new but is very dead, despite it will not have done 10,000 miles. With the breaker point distributor I got the truck running again and very well, indeed, but with a few items.

With the connection from the starter motor removed and contact on, I have 11.5 volt on the battery side of the coil (12.5 volt when points are open). The original service manual says this voltage should be 5 - 5.5 volt, otherwise I’ll burn the points. So the resistor wire is not present. Primairy part of the coil has 1.5 ohm, as it should be. Would adding a universal 1.5 ohm resistor between coil and main switch do the job?

The wire coming from the starter motor gives already 12 volt when contact is on. Probably the starter coil is not equipped with the proper switch. The starter coil has been replaced few years ago. I presume adding a relay, commanded by starting power will be sufficient to add the extra wanted voltage on the batt-side of the ignition coil?

What’s the feeding voltage of a HEI? The full battery voltage?


Yes HEI uses full Battery voltage. With out the resistor on the points type dist. the coil will over heat and
can blow up. I have seen others use a second coil in series to drop the voltage, so your 1.5 ohm resistor
should work fine.

Be sure to check markings on the coil. The coils can be purchased “for use with external resistor” or if no markings ---- use full 12v. Will have internal resistor.

DJ, Dodge vehicles put the ballast resistor right on the firewall but I don’t know what the value is. I have a few around here somewhere. They stopped using resistor wire way way back in the 60’s. You can probably use some old toaster (nichrome) wire to make whatever you need … Here’s a picture of my current fuel pump setup
Old oven nichrome wire to get the voltage to the fuel pump down to 4 volts.
Stay well, Mike L

hi all, Im new so just looking at these older texts. Over the years I have used the mopar resisters alot on old 6volt systems, to change them to 12 volts,and yes they will work on non resister coils.

It took me a long time to accept it but i’m all for hei now days.Only problem I ever had was modual and once a broken or shorted {don’t remember} wire from the pick up coil from the movement of the vacume advance That being said I do have my old standbys stashed away. Just because