HEI or not ?

[Boog]

I have long thought all GM's had HEI ignition since 1974 until now.
When looking up ignition modules at O'Reillys and Rock Auto there are GM genuine HEI and W/O HEI ignition modules available. The images and info are the same so what gives?
Also an AC Delco module listed for my 91 looks nothing like the others.
Who is GM genuine if not AC Delco?

https://www.rockauto.com/en/catalog/...ule+(icm),7172

[Boog]

Also look at the low cost of oxygen sensors at Rock Auto compared to the parts stores. This can't be right?

https://www.rockauto.com/en/catalog/...2)+sensor,5132

[Just call me Sean]

I don't know what the non HEI one would be used for. GM genuine is just a brand name. That other one is the electronic spark control (ESC).

[special-K]

Listing is either wrong or there are industrial applications (or some other thing) I don't know about. Not sure if AC Delco only offer GM designs.

I went to NAPA a couple years ago for an HEI coil and they didn't have anything listed for OEM. I was stunned and amazed. It has been since '95, but stop supplying such a widespread common replacement part when you are in the business of selling replacement parts? I had the guy dig deeper, but he still came up blank. He said "I can order you an Accel or MSD". As I turned to walk out I said, "So can I"

[Just call me Sean]

AutoZone has similar listings. One labeled as non-HEI and the others don't specify.

[Boog]

Well I know better than ask one of those young counter jockeys. I may yank the module out and get the part number off it and see if I can match it up.

Did either of you check out those cheap Rock Auto 02 sensors? Compared to O'Reillys and others RA is dirt cheap on those. If that's real?

[Just call me Sean]

Rock Auto is known to be cheap. I buy from stores I can walk into whenever possible.

[special-K]

Originally Posted by Just call me Sean

Rock Auto is known to be cheap. I buy from stores I can walk into whenever possible.

So do I, but I don't like my NAPA store anymore since the old manager (and a couple good countermen) left. I used to rant about that place and give people hell for buying online. I have begun buying from the underdog Car Quest store in the old movie theater on Main St, even though they are for all intents and purposes Advance Auto, which is up the hill in the shopping center. The smaller the business the more I like to patronize.

That said, I do buy a lot from Rock Auto these days because they often have the better parts than the big box boys. NAPA has gone downhill, IMO. They are just the earlier version of big box. Back when you had the option of independant parts stores, I never set foot in NAPA. As things changed, they became my default store. Rock Auto offers AC Delco whenever possible as well as Timken bearings, for instance. And at reasonable prices. Their listings have also always been correct. The blower motor resistor I recently bought is a Genuine GM part

[speedygonzales]

Originally Posted by Boog

I have long thought all GM's had HEI ignition since 1974 until now.
When looking up ignition modules at O'Reillys and Rock Auto there are GM genuine HEI and W/O HEI ignition modules available. The images and info are the same so what gives?
Also an AC Delco module listed for my 91 looks nothing like the others.
Who is GM genuine if not AC Delco?

If your distributor had the coil on top of the cap, it would be HEI but since it does NOT, it's non-HEI. So obviously your coil is located elsewhere.

Your ICM would look like this


I'm not sure about yours, but most modules require heat sink compound

GM parts are made by AC delco and a few other names are sold as well from the same sources.

I would stay away from some sources of O2's. Bosch being one of them. My truck never worked with Bosch.

[Boog]

Yes the coil integrated larger diameter dist cap was the identifier for an HEI (high energy ignition) system from the beginning but somewhere around the early 90's GM separated the coil and cap again but still retained the hall effect, coil pickup design. It has been my assumption that this system is still HEI since it is of the electronic ignition design. I also assumed GM removed the coil from the cap in order to use a smaller diameter dist for under hood space concerns.
The product listings @ RockAuto and O'Reillys is the confusing part.
The images of those ICM's are the same and the product specs are the same but one says HEI and the other says non HEI. As far as I know there was only one ignition system used on these 88-98 trucks. And all those listed say they do fit a '91 Chevy truck. I'm just looking for some clarification on these parts. Thanks

[Just call me Sean]

Yes HEI doesn't have to have the coil in the cap. That was just the first design.