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This is currently installed in my 72 350. Its a remanufactured engine with a block date code of 74. Can anyone help identify this ignition system from the photos below? Thanks in advance.
Looks like a HEI with a aftermarket vacuum advance can.
Please pardon my ignorance but does the integral coil in the distributor cap reveal that it is HEI? Is there a distinction between HEI and electronic ignition? I see three references to distributors for a '72 - regular with points, electronic and HEI. I'm unsure if mine is old school electronic or true HEI?
The coil in the cap means ONLY one thing.
this is a HEI distributor. This was not offered in 72 by the factory. This was installed later. If your cable drive tach still works this is definitely a aftermarket HEI. A HEI is a electronic ign. But not the type offered in 72.
There are many, many copies of the HEI distributor out there. Probably the most copied ign. system ever.
The aftermarket makes them to fit just about anything from Ford to Toyota but of course the originals are a GM Product.
there are super cheap knock off's and really high quality replacements like the DUI Distributors.
your photos don't show the sides or the insides. So a bit hard to say what you have there.
But it sure isn't factory on a 72!
Perhaps this helps a little. The HEI Distributor came out with the 75 model year. And it's a great Distributor. But later C3's also used electric tach's
The coil in the cap means ONLY one thing.
this is a HEI distributor. This was not offered in 72 by the factory. This was installed later. If your cable drive tach still works this is definitely a aftermarket HEI. A HEI is a electronic ign. But not the type offered in 72.
There are many, many copies of the HEI distributor out there. Probably the most copied ign. system ever.
The aftermarket makes them to fit just about anything from Ford to Toyota but of course the originals are a GM Product.
there are super cheap knock off's and really high quality replacements like the DUI Distributors.
your photos don't show the sides or the insides. So a bit hard to say what you have there.
But it sure isn't factory on a 72!
Thank you for this information. The engine was rebuilt recently to a mild/moderate performance state (intake, heads, rockers, cam, carb) and produces around 350-400HP. The donor engine was from a 74 based on the block codes. My neighbor who I will describe as an "Old school Chevy Guy" commented that it was surprising for them to build a mild performance engine and put an old style Delco ignition back on. I told him that the car was sold to me as having HEI ignition and that opened up this conversation. To your point I've seen dozens of ignitions for sale from $50 to $500 that all look the same. Some descriptions state HEI but some just say electronic and I was unsure if that was the same thing. So here is my takeaway from your information - It is an HEI ignition and therefore should not have points or a conventional mechanical rotor (I believe HEI uses magnetic sensors?) but it could be a very cheap HEI or a better one and only examining it closer for brand / numbers will reveal that.
Thank you for this information. The engine was rebuilt recently to a mild/moderate performance state (intake, heads, rockers, cam, carb) and produces around 350-400HP. The donor engine was from a 74 based on the block codes. My neighbor who I will describe as an "Old school Chevy Guy" commented that it was surprising for them to build a mild performance engine and put an old style Delco ignition back on. I told him that the car was sold to me as having HEI ignition and that opened up this conversation. To your point I've seen dozens of ignitions for sale from $50 to $500 that all look the same. Some descriptions state HEI but some just say electronic and I was unsure if that was the same thing. So here is my takeaway from your information - It is an HEI ignition and therefore should not have points or a conventional mechanical rotor (I believe HEI uses magnetic sensors?) but it could be a very cheap HEI or a better one and only examining it closer for brand / numbers will reveal that.
It will have a rotor and mechanical advance weights.
It looks identical to the aftermarket tach drive HEI that was in my 73 big block.
There were no part numbers or manufacturers name anywhere on it.
When I wanted to replace the cap and rotor, I had nothing to reference for their replacement, so I ran it as it was, trouble free for 7 years until the car came off the road for its restomod.
I installed a new tach drive MSD in the new engine with a 6 AL box.
Last edited by OldCarBum; Aug 8, 2024 at 12:37 PM.
OP, your current distributor is a GM HEI (or at least an aftermarket copy), and if it is working well, leave it alone. There is nothing out there that will provide a significant enough performance/reliability advantage to justify replacing it, in my opinion. The GM design HEI's were just that good.
Now, if you are just wanting to freshen it up with cap/rotor/module/coil, I'd choose parts for a 75-79 Corvette, but truthfully, literally any V8 Chevrolet vehicle from that timeframe will have the same HEI maintenance components.
Plug wires, go with a 75-79 Corvette again, this should be the longer style that routes underneath the exhaust manifolds.
There is such a huge variety of aftermarket and factory HEI support out there, and it's been that way for 40 years.
As an example, I'm running a $50 aftermarket tach drive HEI and $26 under-header plug wires, and they've been fine for thousands of miles.
Oh, and you may want to look at updating it with a spring kit, to fine tune your advance. Search on these forums, there's tons of threads on ignition tuning.
Yup, it could be a cheap one or a really good one. The really good ones are generally well marked as to brand and origin. That said a lot of guys have had good luck with cheap ones. How it curved and how the vacuum advance timing is set up will be the real questions. If the car runs to your expectations and doesn't run hot or ping. Just run it.
checking it's operation would be high on my list but I'm picky.
Yup, it could be a cheap one or a really good one. The really good ones are generally well marked as to brand and origin. That said a lot of guys have had good luck with cheap ones. How it curved and how the vacuum advance timing is set up will be the real questions. If the car runs to your expectations and doesn't run hot or ping. Just run it.
checking it's operation would be high on my list but I'm picky.
Well, speaking of that I am actually trying to track down an ignition problem now. I have 12V at the "BAT" terminal on the distributor and good fuel flow but no start. My next step is to see if I have a spark. If no spark I'm assuming the HEI / coil might be dead and need replacing anyway. By the way, I'm from Perth. I see you are in Qld.
Yup I'm over here in Queensland. I have about 1 3/4 spare HEI distributors. As in I got a lot of bits.
no spark? You do have 12V. Plus to the batt terminal on the RH front of the distributor?
remove cap and make certain the rotor is turning when you crank the engine. Check the wiring from the pickup winding to the module. Check the carbon button inside, center of the cap. If everything looks great. Yes the coil can be tested. If the coil checks out replace the module. The aftermarket modules are known to fail.
Yup I'm over here in Queensland. I have about 1 3/4 spare HEI distributors. As in I got a lot of bits.
no spark? You do have 12V. Plus to the batt terminal on the RH front of the distributor?
remove cap and make certain the rotor is turning when you crank the engine. Check the wiring from the pickup winding to the module. Check the carbon button inside, center of the cap. If everything looks great. Yes the coil can be tested. If the coil checks out replace the module. The aftermarket modules are known to fail.
Thanks for this info. I used a cheap spark plug tester inline between the distributor and #1 lead and see flicker when cranking but no start. Plenty of fuel. Is there such a thing as weak spark?
Actually, there is a such a thing. But this being the issue with a HEI is highly unlikely. Stop being lazy with your cheap spark tester. Start pulling spark plugs. Are they fouled? Connect plug to wire and ground to engine. How's the spark look?
or use a inductive pickup timing light. Does it flash when cranking the engine?
Actually, there is a such a thing. But this being the issue with a HEI is highly unlikely. Stop being lazy with your cheap spark tester. Start pulling spark plugs. Are they fouled? Connect plug to wire and ground to engine. How's the spark look?
or use a inductive pickup timing light. Does it flash when cranking the engine?
Several plugs I checked look good but I can not discern a spark while cranking. I should also have mentioned that the light from the spark plug tester was a dim orange not blue/white. Plug leads look new. I'm really leaning towards thinking its a bad coil or another fault with the HEI. Its definitely a no brand HEI and the plastic cap looks older. I'm thinking I'm just going to buy a new MSD or other known brand, swap it over and see what happens. Worse case I end up with two distributors.
Before you start spending more money, check one thing first.
Is the 12vdc wire going to the distributor, the resistor wire (usually referred to as the pink wire)?
If so the resistor wire will drop the voltage to about 10.5-11 volts to the distributor during ignition cranking.
This was done to protect the oem points/condensor while cranking the engine.
HEI and any electronic ignition needs a full 12vdc while cranking.
Using the resistor wire may work for a while on some engines, but they get old and the additional resistance in the wire will prevent the engine from having enough voltage to the system to allow it to generate a good spark.
There are several threads regarding this common issue here on the forum, but you really need to run a dedicated 12vdc wire from the fuse block.
Check the voltage at the distributor during cranking and let us know what you find.
Last edited by OldCarBum; Aug 8, 2024 at 01:03 PM.
Before you start spending more money, check one thing first.
Is the 12vdc wire going to the distributor, the resistor wire (usually referred to as the pink wire)?
If so the resistor wire will drop the voltage to about 10.5-11 volts to the distributor during ignition cranking.
This was done to protect the oem points/condensor while cranking the engine.
HEI and any electronic ignition needs a full 12vdc while cranking.
Using the resistor wire may work for a while on some engines, but they get old and the additional resistance in the wire will prevent the engine from having enough voltage to the system to allow it to generate a good spark.
There are several threads regarding this common issue here on the forum, but you really need to run a dedicated 12vdc wire from the fuse block.
Check the voltage at the distributor during cranking and let us know what you find.
Before you start spending more money, check one thing first.
Is the 12vdc wire going to the distributor, the resistor wire (usually referred to as the pink wire)?
If so the resistor wire will drop the voltage to about 10.5-11 volts to the distributor during ignition cranking.
This was done to protect the oem points/condensor while cranking the engine.
HEI and any electronic ignition needs a full 12vdc while cranking.
Using the resistor wire may work for a while on some engines, but they get old and the additional resistance in the wire will prevent the engine from having enough voltage to the system to allow it to generate a good spark.
There are several threads regarding this common issue here on the forum, but you really need to run a dedicated 12vdc wire from the fuse block.
Check the voltage at the distributor during cranking and let us know what you find.
Hi, Thanks for your ongoing help. Here is my voltage data:
- Fully charged battery with no terminals connected: 12.99V
- Battery with terminals connected and everything off: 12.99V
- Ignition pin in fuse panel with ignition on: 12.7V
- Distributor BAT terminal with ignition on: 12.58V
- Distributor BAT terminal while cranking: 9.96V
- Inline plug tester while cranking: no glow at all now
So.... looks like the resistor wire is still in place?? I do have a wire coming off the IGN terminal in the fuse panel but it is light gauge (16 AWG) and runs up behind the speedo somewhere. It is not the same wire that runs to BAT which is 12 or 14 AWG.
Can anyone identify this ignition system?
