HEI Conversion question

Yeah I'm running an HEI special at my house! :laugh:

Attached is a picture of the 4 boxes that the HEI units came from. When my friend picked up two more today, he had one of the same black ones, and just picked up that gray one which is the "select" which costs more, I don't know why. Beefier maybe? I don't know haha

With nothing connected, resistance between W and G were 9.85 k ohm

For resistance on W and ground, and G to ground, I had to have the ground wire hooked up to the battery to get a reading. Is this correct?

Ok, I'm at work right now, so it make take a little while before I can get a sketch up... but I think It may be simpler than I thought.
This is really just a best guess based on the tests you did, so it's about a 60% to 75% chance it will work.

So try the original circuit again, but this time leave off the diodes and resistor.
Connect the blue pickup wire directly to the ground of the 1-4 module.
Connect the red pickup wire directly to the ground of the 2-3 module.

Black pickup wire still goes to G on the 1-4 module.
Yellow pickup wire still goes to G on the 2-3 module.

As with anytime Dyna coils are used, make sure there is at least a 1/16" gap between the screw head and the standoff of the coil. Vibration can sometimes cause the screw head to short against the standoff.

If I get called away, I'll try to post here first to see where things stand.

freebyrd24 wrote: Yeah I'm running an HEI special at my house! :laugh:


For resistance on W and ground, and G to ground, I had to have the ground wire hooked up to the battery to get a reading. Is this correct?

Yes, if you are still making readings from the battery's negative post.
The photo showed the modules disconnected from the battery, so in that case, the black meter lead could go to the bolt you are using for ground.

I'll try to locate my CBE4P. I think it's here at work somewhere.

Thank you for taking the time while you are at work, I really appreciate all of this help and troubleshooting! Hopefully it will help out in the future on this mod.

So real quick, you want me to hook this back up to the bike? So I am taking out the resistors and diodes, and running the blue and red wires from the pick ups right to ground. Do I need to ground it to its specific module? I thought the modules were grounded together anyway?

freebyrd24 wrote: Thank you for taking the time while you are at work, I really appreciate all of this help and troubleshooting! Hopefully it will help out in the future on this mod.

So real quick, you want me to hook this back up to the bike? So I am taking out the resistors and diodes, and running the blue and red wires from the pick ups right to ground. Do I need to ground it to its specific module? I thought the modules were grounded together anyway?

Correct on all accounts. However, the pickup signal will be sensitive to the high current noise in the ground connections, so it may be better to use the actual ground terminal on the respective module. In fact there may be enough noise etc. that it may cause problems. Fot that, I will probably develop a better method of getting the pickups to ground. Perhaps I will use a scheme incorporating W.

I would like a circuit that works for all possible brands of modules, so the one you make now may be temporary anyway. If a replacement module is purchased in the field, it would be good if they were all universally useable.

I didn't find the CBE4P. I have a Duralast DR100 and I think a non-marked Wells DR100. They both measure 1.3v on W and G as expected, when using a 9v battery to power the module. This may be a quick easy test... using a 9v battery to determine the module type.

I have spark!!! I put it on the bike as you described and I have spark! I can make a crude drawing for you later on what I did if you would like to see. Now I need to see if the beast will run! Lou, you are the best!

I'm glad we are at least making progress. I'm headed to Oreilly's if I can break away from work.

In the meantime I found a couple of really old factory GM igniters. I bought them a few years ago on ebay, but never tested them. They are pretty dirty, but seem to work.

Guess what, they work differently from the Wells and the BWD version. So now there are three types to check for.

Ughh. That's a lot of testing and writing to do.

Am I all set to go ahead and try to fire the bike? Or is there something more we need to do to make it better?

I think it can fire up, but to be on the safe side you might want to try grounding the W terminal. If it still fires up with W grounded, then I would keep it like that for now. If it does not fire, then leave W disconnected.

I won't know which way is preferred until I get one on a scope.

Well, don't ground that W terminal. That creates a lot of noise.

I just tested a BWD CBE4P. It is totally unlike any other 4 pin HEI module. It is no longer based on the MC3334. No wonder it was behaving so oddly.

It is a far smarter module. It controls dwell very intelligently. At lower RPMs, the dwell will be threshold based, but as the RPMs go up it tries to maintain about 5 msec of dwell. To do this, it reduces the rest time, but holds the dwell time steady. As RPMs increase, the rest period drops to about 0.6 msec, at which point the dwell time once again starts to reduce as RPMs go up. This is to ensure there is adequate time for the coil to discharge.

So..... connect the red and blue pickup wires to their respective module's W terminal.

That should do it.

Make sure to check the timing with a strobe. Since the thresholds are not constant, there can be a little altering of the firing timing, so you want to make sure the advance doesn't accidentally go too-advanced. It will be slight, if any, but you want to be safe.