When i talk about this things...i usually say that black plastic thing with some metal tabs... and the other guy says oh yeah the ignition module...the only thing i can say here they are a damn good piece of electronic,they lasted on our cars for 27 years,bougth one from ecklers last year it lasted for 3000 miles... put again the old GM one...

 

It's not the voltage. I've read, but never seen in person, concern about magnetic coupling issues between the top mounted HEI coil and the pickup coil. Somewhere someone felt/experienced a concern about a drivability issue, and a particular pairing of the ignition coil part number and the pickup coil part number was supposedly more resistant to this coupling issue. As I mentioned, I have no first hand information or engineering data to determine the validity of this issue.

 

Interesting. Thanks for sharing the pics.

 

after years...and years of making things work, and working around things that you wouldn't think would work together but did, I think you folks are over thinking an issue that doesn't exist. kinda like contemplating belly button lint. BTW chevys been using this distributer since the real early 70's , that a pretty good track record, all it does is work

 

Believe it or not, there's actually other guys here on the forum that have been making things work for decades too, partner.

OBTW, good luck telling your boss that he's just overthinking any issue, particularly if that issue is potentially in a million cars a year.

 

if it was in that many cars , you would see more of it , besides just you two. btw , no boss for over 30 years now. hope this helps

 

The details of the GM HEI module input circuit are similar to the technical description of the Nat Semi 1815 chip shown here: http://www.national.com/ds/LM/LM1815.pdf

The application notes contain basic design info.

The back end of the 7-pin HEI didn't change a lot from the original GM 4-pin unit of the late '60's. See the Motorola part sheet for the MC3334:
http://www1.jaycar.com.au/images_uploaded/MC3334R0.PDF


The relationship of the pick-up coil(VR) phase to the 'zero-crossing' HEI trigger are shown there too. Generally if you connect the wrong phase you throw the spark signal off by quite a bit.


The relationship of the 7-pin VR pickup, DRP, and spark timing are shown on the B&G figure here:
http://www.megamanual.com/ms2/heiest.gif
edit - that URL is coming up wrong - try www. megamanual. com /ms2/ heiest.gif without the spaces

There is a VERY modest amateur ignition design discussion here, along with a comparable circuit used by MSD and SGS:
http://www.corvetteforum.net/c4/doctorj/heicoilinfo.htm


This info is used to interface different ECMs, trigger wheels, and the like with the Gen 1 small block FI hardware. FYI, the 7-pin HEI system has much in common with the NORTHSTAR DIS package (given a different trigger wheel and VR pick-ups) which will plug right in to the P4 ECM circuits. As such, knowing how these things are put together helps folks who enjoy modifying C4s for improved performance.

That never struck me as 'over thinking' a better way to do something.

HTH

 

now thats good tech

 

I'm in the market to buy a new Ignition CM. What do you recommend?

 

you're going to hear a few opinions about it , but my opinion is either stock or dui, you're looking for reliability, no matter what fancy words they use or how many ways they explain things , they all do the same thing.

 

I'm rethinking the wisdom of my responding to your posts, when it frequently appears you didn't bother to first read my post before responding to it. I said I've never seen the magnetic coupling issue, and only recently read somebody's comment about it, and have seen no actual engineering evidence of its existence. I don't know how else to make my point clear to you.

Regarding no boss, it doesn't help, and it doesn't hurt. I don't care either way. I'm going to take a wild guess that you are not designing and manufacturing a million parts a year that go into a million different cars. If you were, there's a good likelihood that you would have a boss somewhere.

 

I heard that the pickups have different wire colors that differentiate the different versions. The spare pickup coil I have has green and white wires. I have a vague recollection that some have a yellow wire instead of the white one.

I try to put out accurate information. Please add your knowledge.

 

Excellent , Cliff, Thanks for getting this back on topic and being the professional that you are, many thanks, bob

 

Not trying to beat an old horse, but can you point me to that eye opening personal slur you say I made (and therefore lost esteem, as it were)?

Just trivial history, but in 1983 I was assigned to design a replacement IC for the seven terminal module pictured in the original post, and I did. It worked, and met the specs, but I couldn't achieve a great enough cost reduction in my design (compared to the production IC) to pay for all the required validation testing and documentation updates needed to satisfy the customers at the assembly plants whenever new/updated/redesigned components are put into the production stream, so the project was cancelled. I was disappointed, of course, but cost factors are a way of life in any business, and particularly when the cost reduction is small compared to possible warranty cost risk when introducing new parts in high volume production.

 

Take the bickering to PM's gentlemen. If you don't have anything to add in relation to the OP's post, STAY OUT OF IT.

 

you're absolutly right, I apoligize for my part in this, bob

 

A bit off topic but questions i have.

wiring diagram says bat voltage to pin "p", i Show 12.63.

sould pin "+" have the same voltage while ignition is in run? I show 1.43. i belive module to be bad. Oriliey's computer says it is good.

my spark plug and ohm meter both confirm no spark condition. fyi all other test are ok.

 

The pink wire going to the distributor comes from the ignition switch. That pin is connected to the three pin connector behind the ignition and tach connectors and also to the ignition coil.

The three pin connector has a cable that goes into the front of the distributor. The ignition voltage is the red wire in that cable and it connects to the "+" pin of the ignition module.

You need to have all the connectors plugged into the distributor cap to see the ~12 volts on the "+" pin.

 

Great, you guys are giving out the secrets to the IRON MAN suit!
I took one of these apart back in the late 80s and I still have NOOOOO idea what the heck I'm looking at.. thanx for helping me understand the "how" it works.

 

Thanks, aside from the many issues i am having w/the distributer i was told by orileys that the module was good, then i purchased a new one. and had the same voltage readings. the ground on compasitor and 5 pin side are both good.

the "+" pin just does not show 12.63. hooked a jumper from jumper box to top red connector and coil and fire. damn this thing...new pick up coil, coil, rotor, cap, rotor spring.