Stock GM Hei ?

[Daves72'GMC]

I have a '72 GMC with the 402BB and I want to change my stock distributor to a stock GM Hei and a friend of mine gave me an Hei. People on the board said for me to get a '73 Hei. I took my Hei down to Napa and their Hei was a little different than mine. My hei has plates right under the Cap and no rotor and has a codensor and a black electrical piece with 2- screws and says GM on it. Napa's Hei doesn't have the plates right under the cap and looks to have a rotor on it. The Napa guy gave me a price for the rotor , so his uses a rotor. Is mine a later Hei or a computer controlled hei? Which one do I need? I don't want to use mine because it's very dirty and I don't want to go through the hassle of rebuilding it. Thanks everyone.

[CPNE]

It should have a rotor under the cap. The HEI you need is 4 pins on the module. If you remove the black thing that says GM how many pins on it? FYI, I'm sure there is a better way to tell so before going to that trouble, you may want to wait for a alternate response.

[Blue Beard]

Wish someone would do a complete run down on the HEI.

I've heard so many diffenent views even form parts houses.

[Daves72'GMC]

Mine has prongs at each end of the piece that says GM on it and each prong has 2 prongs, and the piece that says GM on it has 2 srews which hold itin palce.

[CPNE]

Sounds correct. Does it only have 4 leads that plug into the cap?

[Daves72'GMC]

no, mine has only has 2 form the wire to the cap and mine does not have a rotor.

[pound41]

I have seen different amounts of leads at one end or the other on that black thing(control module) based on the year of the distributor. So that is the only real important part as far as replacing things that is what usually fails when its not getting fire

[jhow66]

HEI did not start until late 74 on Cadilliac. There is a # on the side of the housing such as 1103532 that can be looked up to tell what year and car it was used in and the advance rates. The computor controlled HEI will have 2 sets of wires coming out of the base--one with 3 wires and one with 4 wires. This is the one tht you do NOT want. Get the one with 3 wires. If you like get the # and I will look it up for you.

[WRMZ71]

that little thingy that says gm on it you guys were talking about is the ignition module. I believe it is what limits your red line to around 5000 rpm bone stock. Sometimes when these go bad when cold engine will run fine but when heated up it will just die and it won't start again till it cools down. This problem is sometimes caused by the lack of dielectric grease underneath it. The ignition module is an easy fix. Any parts store should be able to test them. I've had em checked at napa's and autozones and advanced autos before. There only about 15 bucks so it's an easy fix. You should have a rotor on there too. But then again I may be wrong. As far as not getting fire the main things are your hot wire going into the distributor, your coil, your ignition module, and then last off your pick up coil. As long as your plugs and wires are ok the next thing i'd do is to check the cap and make sure it isn't burnt anywhere. Then check the rotor this is usually a culprit too, as it will get little burnt black streaks on it. then check the ignition module and if all that stuff checks out your pick up coil is probably bad and it's about 15-20 dollar range too. Problem is you have to tear apart the distributor to put it in. HEI's came out in 75 but they might have come out in late 74 like the other gentlemen said on cadillacs

[BLAZERMAN]

The computer controlled hei will not have a vacuum advance, they all have to have a rotor.

[Daves72'GMC]

Thanks guys, I got the one with the 3 wires and the vacuum advance. Mine didn't have a rotor on it and I see where it goes on now. I'll send it out now to have it recurved.Thanks again. Dave

[Longhorn Man]

A good stock GM module WILL fire over the 4500 - 5000 RPM that so many ppl say. I have had mine to 6500 more times than I can remember and accidently up to 7500 once. (Bout crapped my pants on that one too)
Be very carefull on those $15 parts store modules. They are pretty much all junk and have given the HEI a bad rap. The GM one is 10 times better,a nd will run over 100,000 miles.
I would pull one out of a junk yard for 20 bucks before I would ever run a parts store $15 one.