HEI ignition conversion

[Raphael]

Hi people

just to let you know that a GM HEI ignition module works nicely , right in place of the stock ECU.
I just finished a test conversion, the car started immediately, I didn't even have to correct the initial timing. I still need to test drive but as far, the engine idles and revs fine.
Like some Duraspark conversion we saw in the past, it's very easy to connect 4 wires from the module to the stock harness. for ease of test and sharing, I installed the setup inside a stock Bosch enclosure. so i can connect/disconnect at will.
for a clean installation, maybe I will put the device (module + heatsink )on the firewall in place of the stock ballast, with the correct coil allowing to get rid of the resistor of course.
I chose GM module for bulletproof, compact design.

http://stainless.delorean.fr/gallery/3_1347549122.jpg

http://stainless.delorean.fr/gallery/3_1347549664.jpg

[Spittybug]

Nice! Tres bien fait!

Can you post another shot of the wire connections (which HEI contacts to which pins on the connector) so that others can do the same?

[Raphael]

here it is. no secret.:hihi:

http://stainless.delorean.fr/gallery/3_1347551813.jpg

[Raphael]

PIN B - to #15 : +12v ( green wire )
PIN C - to #16 : to coil ( white/slate)
PIN G - to #7 : to pick-up coil ( inner blue wire )
PIN W - to #31d : to pick-up coil ( outer black wire )
Mounting screw - to #31 : ground
Warning ; don't forget to ground the module to frame, AND the black metal frame supporting all ECUs to correct ground.

[Spittybug]

Very nice, thanks for that. Fortunately the stock module is not that expensive and doesn't often go bad, but it's always nice to have an alternative that is mainstream.

[Raphael]

mine was turning bad slowly. it was still working ,but would miss sparks randomly, and crash passed 3000 rpm.
and here in France, we experienced a few ECU going bad, I think the electronics inside are getting old... so I did buy a new stock ECU but couldn't really trust it in the long run.
for a few $$ you add a new function, among other benefits ; self-adjusting dwell time , compared to the Bosch fixed- dwell.

[Jeff K]

mine was turning bad slowly. it was still working ,but would miss sparks randomly, and crash passed 3000 rpm.
and here in France, we experienced a few ECU going bad, I think the electronics inside are getting old... so I did buy a new stock ECU but couldn't really trust it in the long run.
for a few $$ you add a new function, among other benefits ; self-adjusting dwell time , compared to the Bosch fixed- dwell.

Great find! Thanks for sharing.
Jeff

[Bitsyncmaster]

Good work. I would hard solder the wiring. I don't trust insulated terminal crimps anymore.

[Raphael]

everything is soldered :) I just used rubber covers instead of shrink sleeves, over the solders

[nkemp]

Can you show how this gets wired with the correct coil and without the resistors (I always hated how they look)?

Thanks & good sluething,
Nick

[nkemp]

So this thread got me interested and I came across this. Adding to this thread as FYI for those interested.

The Popular Hot Rodding site made the following points:
- Some skip this step but good practice is to coat the bottom of the module with silicone dielectric grease for insulation and a bit of thermal transfer. The module NEEDS to be on a good heat sink.
- Some folks use heat transfer paste (like used on PC CPU's). Trouble is that it could dry up in hot underhood conditions. Depending where you install in the D, this may not be an issue. If mounted in the original spot, engine heat will not be an issue relative to drying the thermal paste. The question is ... does it get hot enough by itself to dry the thermal paste?
- Silicone/dieletric grease will not dry up and works well in hot environments.

[stevedmc]

Can you show how this gets wired with the correct coil and without the resistors (I always hated how they look)?

Steve Rice, Farrar Hudkins, Byrne Heninger, and Bill Robertson among others are running HEI wired like this:

http://sphotos-a.xx.fbcdn.net/hphotos-snc7/s720x720/384059_452072344838021_649006471_n.jpg

The key components are not the ignition module, they are higher coil input voltage, a high ratio winding coil, and much wider plug gaps. Without all of these you will not have HEI, no matter which ignition module you are using.

Steve Rice and Farrar Hudkins are using stock Bosch ignition modules with their HEI. Byrne Heninger and Bill Robertson are using Ford Duraspark ignition modules with their HEI.

Some owners have eliminated the ballast resistors altogether. Wiring the resistors in parallel cuts their resistance in half and increases primary coil voltage to 12-13 volts while the engine is running. Coil input voltage while cranking is same as stock, but the resulting spark is higher due to the higher winding coil and the wider plug gaps.

[Raphael]

yes of course, in addition I already have a MSD Blaster II coil and running wider gap on the plugs, and 8mm wires.
I kept the ballast resistor as long as I used the stock ECU, but now with the GM module, I think I can cut half of the resistor. I would like to get totally rid of it, but not sure if it's safe for the MSD coil. some say it can handle full voltage coupled with a modern ECU, some say no.
reducing voltage on the coil kills most of the benefits of a good coil.

and of course, the GM module MUST be installed on a heatsink with specific compound. ( it comes with the module when you buy it).
the title of this thread says "HEI" because the module itself is commonly referred as a "HEI module" at GM. Technically, a true HEI setup is a hi-voltage ignition using a modern coil like MSD or Pertronix.
the point here , was to offer an alternative to the stock ECU with obsolete electronics. the stock bosch unit works great for a 30+ years old device, but it's becoming oldish.
i like the features of modern electronics like the smart self-adjusting dwell. so your HEI coil gets full saturation at any RPM ;)

[stevedmc]

Byrne Heninger's Bosch ignition module died, thus his upgrade to Ford's version of HEI, so yes indeed: OEM ignition modules do not last forever.

[Raphael]

I just received a reply from MSD Tech support, they confirm that we can get rid of the ballast when using a modern module like the GM HEI.
of course the ballast is still necessary when running the stock ECU.

[stevedmc]

Actually the resistors are there to protect the Bosch coil, not the ignition ECU. A stock coil can not handle more than 8 volts for extended time.

Owners running both resistors in parallel (.25 ohm, 12 volts into the coil) with a stock ECU have no problems.

Byrne Heninger's Bosch ECU died while he was running stock ignition.

[nkemp]

So If I understand this correctly the resistance is there to protect the coil (by reducing the voltage to the coil) and resistance also determines the coil output voltage. For example, the Pertronix coil has built in resistors and depending on the coil as the internal resistance goes down, the voltage goes up. As such, including the resistors in parallel like shown above is reducing the coil output voltage.

The Pertronix coils are:
- 40,000 Volts DC 1.5 or 3.0 Ohm primary resistance (not clear why 2 different resistance values generate the same voltage... but it is all internal so there may be more to the design story)
- 45,000 Volts DC with .32 Ohm primary resistance

The Bosh coil must not have built in resistors which is why the firewall resistors are there. Running the resistors in parallel (reducing the resistance) causes the Bosch coil to throw a higher voltage spark than the series design.

Also, actual resistance used must be a function of the coils voltage design value. For example one coil could be designed for 12 VDC and another 13VDC and if so, the resistance values would be different.

The resistors are not needed for the control module operation.

Did I get that correct?

[stevedmc]

Do not increase primary voltage into a Bosch blue coil or you will burn it up. Only increase voltage into a coil designed for it, such as Pertronix or MSD.

[vwdmc16]

Right, im running full voltage to my MSD blaster II coil with the stock ECU and have had no ignition issues for over a year now.

[nkemp]

Do not increase primary voltage into a Bosch blue coil or you will burn it up. Only increase voltage into a coil designed for it, such as Pertronix or MSD.

Steve you also said
Owners running both resistors in parallel (.25 ohm, 12 volts into the coil) with a stock ECU have no problems.

Doesn't running the resistors in parallel increase the voltage to the Bosch coil?

I'm not trying to cross examine you ... I'm just trying to get a good handle on this and it is a car topic I never really thought about before.

Nick

[stevedmc]

Those owners are using Pertronix or MSD coils, not Bosch blue coils.

If you want HEI, you must change the coil. You can continue to use a stock ignition ECU, but the coil must be upgraded. Increasing voltage into a Bosch blue coil will kill it.

Three things are necessary for HEI:
1) increased primary voltage
2) suitable coil
3) wider plug gap
If you leave any of those three things out, you will not have HEI.

As Raphael pointed out he already had the three necessary ingredients for HEI. This thread is about an another ingredient he has added: an upgraded ignition module that can change dwell time on the fly. Raphael's ignition module also has newly manufactured components, not 30 year old components. He had HEI already. Now he has taken it to the next level.

[nkemp]

Thanks for clarifying!

[DARCOM]

I have been running a HEI for over 5 years now on my Delorean. i have had no problems

[nkemp]

For those running HEI, how has performance changed?

[nkemp]

I've been searching for more detailed info on the GM HEI module(s) and their operation. As some of you may know, the details are not easy to find (you need to filter out all the vendors) and the sources may not be accurate. Here is some info:

-Well worth reading:
- This is the most detailed info I've found... http://home.comcast.net/~loudgpz/GPZweb/Ignition/Hei4pinGmIgnitionNotes.txt


- http://cyberdave.org/HEICoilInfo.html
- Megasquirt info: http://msextra.com/doc/ms2extra/MS2-Extra_HEI.htm


Supposedly:
- "No matter what coil you use you will not need a ballast resistor. The purpose of a ballast resistor is to add series resistance to limit current through the coil. The HEI actually measure the current and when it reaches a certain point resistance is added using the switching transistor to prevent excessive current draw. So basically it has a built-in self adjusting ballast resistor." ...from <http://www.carbdford.com/tech/HEI/hei.htm>
- "For non-computer controlled carbureted engines, the four-pin unit is used since it uses mechanical timing controls (vacuum and mechanical advance). The seven-pin module can be used on non-computerized engines since it does not contain mechanical timing controls, but some early designs used a seven-pin in a distributor with mechanical and vacuum advance in the distributor body, so the seven-pin module would be backward compatible." From <http://en.wikipedia.org/wiki/H.E.I.>
- "...retarding the ignition timing 10 degrees under boost. There is a 5 pin module similiar to the 4 pin but has a tiny connector when grounded will instantly retard the timing 10 degrees." From: http://www.guy-croft.com/viewtopic.php?f=4&t=2708

[Bitsyncmaster]

Pretty cool ideas built into the unit. One thing I question is the coil current limiting. If that is a linear current type limit than that heat sink would have to dissipate a lot of heat depending on the coil resistance.

[nkemp]

so the seven-pin module would be backward compatible.

Others outside the DeLorean community have used the 7 pin version as a 4 pin application. Supposedly the 7 pin handles higher current than the 4 pin should anyone want it. To use a 7 pin version as a 4 pin, do not connect the extra terminals. Someday when you computerize the ignition you can connect the extra pins.

Reminder: I'm subject to being wrong without notice and as such, your mileage (or lack of mileage) may vary. :)

[nkemp]

One thing I question is the coil current limiting. If that is a linear current type limit than that heat sink would have to dissipate a lot of heat depending on the coil resistance.

I think the issue you raise is relative to the "System" nature of these. You can't look at the coil, HEI module, Ballast resisters, etc in and by themselves. They are all interrelated.

Does this help or add value to the discussion?

"The Mopar system uses the positive temperature coefficient of the ballast resistor to regulate the primary coil current with changes in duty cycle (engine rpm). A simple, relatively reliable system for most daily drivers. The disadvantage with the ballast resistor is the slow response time of the resistor resulting in the field of the coil not being fully charged during sudden acceleration ie, a spark that may not be as hot as is possible with more modern systems. The GM HEI module is typically based upon a Motorola (now Freescale) MC3334 IC or equivalent. The MC3334 regulates coil current using an internal variable voltage reference. This internal variable voltage reference is able to respond much faster to changes in duty cycle resulting in a much hotter spark durring times of sudden acceleration and less destructive heating to the coil during low rpm operation. The MC3334 also imposes a 1 msec off time to ensure complete discharge of the coil field during a spark event. At very high rpms coil current is limited due to the slope of the coil's primary charging ramp time which is determined by VBatt and the primary impedance of the coil itself. Some good OEM coils are the Ford "E" core coils and the remote GM coil which is also an "E" core design. The MSD Blaster line of aftermarket coils are also very good coils. Don't be fooled by claims of HIGH VOLTAGE from the perveyors of coils. The voltage developed by the coil will only be as high as the break-over voltage of the plug firing, typically only a few thousand volts. When shopping for coils it is important to look for a coil with a high Joules rating and match the rpm range to your needs. If the coil manufacturer does not publish the joules rating of the coil, walk away and buy somewhere else. Don't use a race only coil on the street. It will just overheat and fail." from: http://www.rx7club.com/1st-generation-specific-1979-1985-18/tfidfis-894669/page5/

[Ron]

Does this help or add value to the discussion?

"...The voltage developed by the coil will only be as high as the break-over voltage of the plug firing, typically only a few thousand volts...."

Elvis we were right! (no troll intended)

[dustybarn]

Pretty cool ideas built into the unit. One thing I question is the coil current limiting. If that is a linear current type limit than that heat sink would have to dissipate a lot of heat depending on the coil resistance.

Absolutely true. I don't think you'd want to use a coil with tooooo low a primary resistance.

[Bitsyncmaster]

Absolutely true. I don't think you'd want to use a coil with tooooo low a primary resistance.

I looked at the data sheet on the MC3334 part. It looks like the part was designed to use our 800 ohm pickup coil which is good. But I don't like the idea of replacing our coil resistors with the heat generating coil driver in the the part. I don't want 50 watts of heat in the cubby hole behind the drivers seat. Much better having that heat back in the engine compartment. You could probably find the correct coil to limit that heat.

That part is hard to find here in the USA.

[Raphael]

After some hours of road test I can attest :
- the GM module doesn't generate high temperatures. the little heatsink that I use (see pics in the first message) is just warm after hours of driving. you can hold it in your hand, and the ambiant temperature of the compartment behind the seat is normal.
- I removed the ballast in order to supply a MSD Blaster coil with full 12v and it won't overheat either. I performed several safety tests , stopping often to check temperatures of both coil and module. everything was normal.

[Bitsyncmaster]

After some hours of road test I can attest :
- the GM module doesn't generate high temperatures. the little heatsink that I use (see pics in the first message) is just warm after hours of driving. you can hold it in your hand, and the ambiant temperature of the compartment behind the seat is normal.
- I removed the ballast in order to supply a MSD Blaster coil with full 12v and it won't overheat either. I performed several safety tests , stopping often to check temperatures of both coil and module. everything was normal.

Good info. What is your primary coil resistance?

[Raphael]

Blaster's primary resistance is 0.7 Ohms.
I had doubts too, that the setup would withstand full voltage so I ran it with the stock ballast at first. Then I received infos from MSD's tech line stating that the coil would work fine combined with a GM module.
It was worth a try , at least. And in the end, it works pretty good without excessive heat.
So I think I get a good combination.
Pertronix coils have a primary resistance of 1.5 Ohms for those who want to be safe ( same total resistance of stock blue coil + ballast )

[nkemp]

It doesn't sound like a problem but if it were, we could mount the module on a heat sink in the engine compartment... possibly where the resistors currently reside. Correct me if I'm wrong but the GM module is weather proof. I believe GM actually did this on some models.

[Raphael]

yes of course, my first idea was to mount it in place of the ballast. the only modification would be to add just one wire between the setup and the coil.
Then I installed everything in a stock Bosch ECU for conveniency during tests ; so I could plug and unplug at will for comparison and in case it would turn bad lol
but now I think the actual setup will stay for good.

[Raphael]

GM actually put the module on a heatsink on the firewall of 90's GM trucks. that's this particular heatsink I used here ( AD Delco # 10474610 ).

[nkemp]

Then I installed everything in a stock Bosch ECU for conveniency during tests ; so I could plug and unplug at will for comparison and in case it would turn bad lol
.

I like the idea of being able to go back to stock should one ever want to (although I can't really think of a good reason). It would be nice if we could track down that connector or another module that used that connector and was available for dirt.

When I was investigating this module, I read that some use trailer light connectors to plug into the original wiring. An interesting idea and a heavy duty inexpensive connector. It could be wired in parallel to our connector (just make sure to unplug the Bosch unit.

[stevedmc]

Byrne Heninger and Bill Robertson used dead Bosch modules to make plug in adapters for their Ford Duraspark modules:

http://sphotos-a.xx.fbcdn.net/hphotos-prn1/532240_357107371001186_1693325183_n.jpg

[nkemp]

The trouble is coming up with the failed modules or knowing what to pull at the junk yard.

[stevedmc]

1980's Volvo ignition modules are under the hood, by the passenger wheel well.

[nkemp]

I did some snooping and it looks like Bosch has/had a solid state plug compatible replacement for our original ignition module 0-227-100-019 and it was called IG-B014. They mounted it on the same heat exchange that our module uses probably for backwards compatibility. Trouble is that when I Google the replacement, the part does not show up and when it does it is over the pond. Could it be that is was used under a different number?

The most useful information I found is the list of other cars that used that replacement module and as such was pin compatible. The cars easily found in the US are (note there was some discrepancy relative to years used):

DE LOREAN 1982-81 DMC 12
PEUGEOT1980-77 604
VOLVO 1982-80 GLE
VOLVO 1979-76 260, 264, 265 Series (75 - 85)
VOLVO 1986-83 760 (82-88 )



13416

[Ron]

Coil input voltage while cranking is same as stock...Stock wiring bypasses one resistor while cranking, so power passes through one resistor. Your schematic shows power passing through two resistors, in parallel, all the time, so the voltage would actually be higher.


...but the resulting spark is higher due to the higher winding coil and the wider plug gaps.The voltage is higher because of the above and because of the wider gaps, not the coil. Induction coils don't throw/push/force/etc sparks. As the article nkemp quoted in post 28 indicates, a coil will supply what the spark plug wants, and that is it. (Similar to putting one million batteries in parallel with a horn...It will not blow any louder than with one battery, just honk a million times more, if you keep hitting the button...) The stock coil is capable of handling .050" gaps, and more. [So why MSD...in short, the "M" is for "Multi", "S" is for "Spark"...deloreans are single spark. Same goes with capacitive discharge systems...a whole different ballgame.]


A stock coil can not handle more than 8 volts for extended time.
Owners running both resistors in parallel (.25 ohm, 12 volts into the coil) with a stock ECU have no problems.Huh? 8V is max but 12V has no problems???


Three things are necessary for HEI:
1) increased primary voltage
2) suitable coil
3) wider plug gap
If you leave any of those three things out, you will not have HEI.
None of these are needed on a stock deloren (and if you choose #2 wisely, you don't need #1) ...if it has a problem, check your grounds :tongue_stick:

[Raphael]

None of these are needed on a stock deloren (and if you choose #2 wisely, you don't need #1) ...if it has a problem, check your grounds :tongue_stick:
yes , to make it simple :
- to get better combustion, you need a better spark.
- to get a better spark, you need to increase plug gap.
- to increase plug gap, you need a better coil
- if the new coil works that way, keep it simple , you're done with the modifications.
- if ever it's not enough, remove the ballast to increase primary voltage. but it's not necessary.
- a new and modern ignition module is the cherry on the cake.

[Bitsyncmaster]

I have to agree that using two resistors is a dumb idea but I guess they did it just to match the coil to our system. Every other old car will use just one resistor that is dropping the current to the coil with the engine running. Then that one resistor is bypassed during starting the engine. That is done to compensate for the voltage drop when the starter is engaged (about 10 to 11 volts on battery).

So if our DeLorean had a one ohm coil, it would have only used the normal one resistor. There is also considerable resistance added in our long harness connections. Remember you need to account the resistance for both sides of the coil. The + side (resistors and wire) and the - side (wire and transistor on voltage of about 1 one volt).

[Ron]

yes , to make it simple :
- to get better combustion, you need a better spark.
- to get a better spark, you need to increase plug gap.
- to increase plug gap, you need a better coil
- if the new coil works that way, keep it simple , you're done with the modifications.
- if ever it's not enough, remove the ballast to increase primary voltage. but it's not necessary.
- a new and modern ignition module is the cherry on the cake.


I basically agree with that...Of coarse this only applies if the given spark is not sufficient for ones goals, and there are thresholds to consider. When meeting environmental requirements, second guessing the engineers is usually a mistake. If ones goal is performance, they should consider that Pertronics, even amidst the sales hype, says, "Every engine responds differently to spark plug setting. In most cases increasing the factory recommended gap by .005 improves the engine performance." (link (http://www.pertronix.com/support/tips/default.aspx#a2)) Given the factory spec of .024"-.028", ~.032" is as wide as one could expect to get without adversely affecting the characteristics of the burn. Considering that the .005" is adding ~20% to spec, .050" (the suggested gap floating around in the threads here), 5 times that, or an increase of ~100% spec, raises all kinds of red flags for me.
Today's engines with .050" (and wider) gaps are part of the total design as (?) said earlier (compressions, chamber shape, flame fronts, burns, fuels, etc, etc, etc are different). It seems that some do not understand this, and, that a lot of people stand steadfast on the idea...IMO, because they saw a marked improvement in their performance when installing a "hot" coil and widening the gaps...but don't consider that, as often said in their posts, the wires are new, all connections were cleaned, timing was set, new cap, new rotor, etc (any one of which could be why) -- "What works" is usually a good idea, but not always the best idea, and often the source of old wives' tales...

That being said, I can see someone changing the ignition to gain reliability (and the cherry on top;-), or even carbing it if they don't understand K-Jet (although I'd go the other direction), cutting the dash for a decent sound system, or whatever, especially if it makes the enjoy their D. But I don't see devaluing my D for what little is offered, even if things worked the way some seem think they do -- Not that I'm a purist by any means, I simply like my D as it is...well...I am in the market for a 5 speed :biggrin:

[nkemp]

Does the ballast resistor "protect" the coil during the spark, between sparks or both?

I read that the GM module dynamically limits current to the coil (likely the 50W heat dissipation potential mentioned above) and thus when using the GM module, no ballast resistor is required. Does this imply that the protection is there during the spark?

Yeah .. I know ... this thread has been "resting" for a while but the question seems to fit the topic.

Nick

[Bitsyncmaster]

It limits the current flowing through the coil when it's saturating the magnetic field. When the current stops the collapsing field creates the high voltage spark. With the smart GM IC, I don't think you would need a resistor but not all GM ECUs use that IC.

[nkemp]

Thanks Dave. I hoped you'd see the question.

Here is more info worth posting herein:

"...If the DC resistance of the ignition-coil primary is so high that a current of 5.5 amps is never reached, the current limit feature does not get used. A 3-ohm ignition coil won't use the current limiter in typical applications. A 2.4-ohm coil probably will use the current limiter a little bit. ... "

I was pondering why the OP Raphael didn't see much heat. It may be partially explained by the coil resistance and the supposed fact that the internal regulation does not come into play if the coil resistance is high enough.

This and a lot more info about this module is available at: http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=9&ved=0CFgQFjAI&url=http%3A%2F%2Fwww.classiczcars.com%2Fforums%2Fa ttachments%2Felectrical-s30%2F40801d1298168167-ignition-problem-hei-notes.doc&ei=VX35UeqMHqKVygG4v4GoDw&usg=AFQjCNFArkwB0jWAwvYsbBE8wKQnYLBCug&bvm=bv.49967636,d.aWc&cad=rjt

[Bitsyncmaster]

Thanks Dave. I hoped you'd see the question.

Here is more info worth posting herein:

"...If the DC resistance of the ignition-coil primary is so high that a current of 5.5 amps is never reached, the current limit feature does not get used. A 3-ohm ignition coil won't use the current limiter in typical applications. A 2.4-ohm coil probably will use the current limiter a little bit. ... "

I was pondering why the OP Raphael didn't see much heat. It may be partially explained by the coil resistance and the supposed fact that the internal regulation does not come into play if the coil resistance is high enough.

This and a lot more info about this module is available at: http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=9&ved=0CFgQFjAI&url=http%3A%2F%2Fwww.classiczcars.com%2Fforums%2Fa ttachments%2Felectrical-s30%2F40801d1298168167-ignition-problem-hei-notes.doc&ei=VX35UeqMHqKVygG4v4GoDw&usg=AFQjCNFArkwB0jWAwvYsbBE8wKQnYLBCug&bvm=bv.49967636,d.aWc&cad=rjt

I remember reading up on that IC when the EFI guys were having problem with their ECUs. It was a pretty nice IC that was designed for our pickup coil and that current control. I think our coil runs about 6 amps. You have to measure the current with the engine off so you don't get the averave coil current but the true current when powered. There is quite a lot of resistance in the harness also that drops the voltage.

[Raphael]

On the practical side, I've been using this setup for one year now, without ballast, and everything is working perfect

[DeloreanJoshQ]

Raphael, what difference in performance have you noticed?
Dave M, can you make and sell these?

[Bitsyncmaster]

Dave M, can you make and sell these?

I thought about a new ignition ECU but start up costs exceed any payback with the number of units that will sell.

[Raphael]

I found a noticeable improvement on idle, low-end torque and overall driving agreement. But don't expect big horsepower gain, it's just that the ignition works at full potential now. I can open plug gap for a good spark and combustion. perfect combustion by watching AFR signals and plug color.
and you can build one easily, GM modules are dirt cheap, you just need a heat sink and a soldering iron. it's plug-and-play, no advance settings required.

ps. don't forget to add a good ground wire from the ECU support plate to the main harness ground, this trick improves greatly the performance of the ignition ECU, and it's noticeable when driving. believe me, try this one ;)

[dustybarn]

I switched to a 4-pin GM HEI module when I de-MSD'd my car (I had intermittent spark triggering and didn't want to mess with trying to troubleshoot it). I didn't have a stock Bosch module, and the GM one was free. I followed the "Lou Dudzik HEI Notes" file referenced in an earlier post and it seems to work well.

It is important to observe the correct pickup polarity. The HEI module expects to see a rising voltage, then triggers on a downgoing zero crossing (as modified by the RPM-sensitive DC offset explained in the notes). I hooked up the distributor pickup to an oscilloscope and spun the distributor by hand to make sure I had the polarity right.

I did run a separate ground wire for the module which goes through the bulkhead and attaches to one of the valve cover bolts.

I have an aluminum heat sink on the back of mine, but depending on the coil resistance it may not be necessary. I'm using a yellow Accel can coil and the module barely gets warm. I suspect I could have probably screwed it directly to the ECM tray without difficulty. Remember that these modules were designed to be mounted inside the distributor, a much harsher thermal environment than under the parcel shelf.

The talk of ballast resistors made me laugh - I once had a Plymouth Volare with a slant-six. The wise owner always carried a spare ballast resistor (in this case a big ceramic block with 4 terminals) in the glove box because they would fail without warning. The telltale sign was that the engine would crank and start just fine, but immediately stall as soon as you let off the key.

[nkemp]

One more thing to contemplate ...

I've read that HEI ignitions can draw up to 25Amps current at start. It may not draw this for long but it is a significant draw. Given the OEM wiring that we often tap into, the quality of some of our old connections, consideration should be given to upgrading the current carrying capacity. Namely going to 10 or 12 gauge wire for both supply and ground. At idle the current draw is not that bad and as the RPM's increase the current draw can decrease based on dwell time. So the issue is start-up current draw. DeLoreans seem to have too many fires... let's not add to the opportunities.

[Bitsyncmaster]

One more thing to contemplate ...

I've read that HEI ignitions can draw up to 25Amps current at start. It may not draw this for long but it is a significant draw. Given the OEM wiring that we often tap into, the quality of some of our old connections, consideration should be given to upgrading the current carrying capacity. Namely going to 10 or 12 gauge wire for both supply and ground. At idle the current draw is not that bad and as the RPM's increase the current draw can decrease based on dwell time. So the issue is start-up current draw. DeLoreans seem to have too many fires... let's not add to the opportunities.

I would think if that start current is true, it would be very quick to drop to normal. A quick start up current would not require heavy wire upgrade since the time is so short. Would be interesting to read the current timing on an O-scope. By the way, an incandescent bulb draws many times the rated current when you first turn them on and they do not need wiring to handle that large surge current.