GM HEI: Cheap and Extremely Effective Ignition Upgrade

If it's broken or just needs tweaked

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SchoolDaGeek
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Joined: Fri Aug 26, 2011 8:36 pm

Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby SchoolDaGeek » Tue Jun 18, 2013 10:55 pm

Loudhvx wrote:
To test the igniter and coil, hook everything up except the G terminal. Then just very briefly apply and remove voltage to the G terminal. Removing the voltage will cause the spark. The voltage can be anywhere from 2 volts to 12v. But make sure G is not cnnected to anything else.


I will try and remember this test for tomorrow...
Buy New, Wire Right. BNWR. LOL

SchoolDaGeek
Posts: 147
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Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby SchoolDaGeek » Tue Jun 18, 2013 11:10 pm

MHolmes wrote:Wow pretty good deductive skills, that is is my wiring.


Pretty sick setup, love the breadboard, hope it is a bar-hopper and not your primary ride unless you spray it with that waterproof rubber you see on TV.
Buy New, Wire Right. BNWR. LOL

SchoolDaGeek
Posts: 147
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Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby SchoolDaGeek » Tue Jun 18, 2013 11:27 pm

Even though resistors are not polar, it would make sense to get them right, here are the basic resistors that can be used on 530 Ohm reluctors.

Image

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Buy New, Wire Right. BNWR. LOL

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Volker_P
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Location: southern Germany

Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby Volker_P » Wed Jun 19, 2013 1:46 am

SchoolDaGeek wrote:
Volker_P wrote: As far as I remember the ignition switch contains springs and balls. Nevertheless a good idea to clean off there after 30 years. Especially if you have a suspiciously high charging voltage that even rises if you switch the headlight on or your ignitors just did melt.


I remembered this conversation from way back when Matthew/Masika was telling me about his melted ignitors, that is why I have to go down and go through the harness for him, I really don't have any other explanation for his troubles, I did find one original resistor I was using and it was the proper 3900Ohms (3.9k), orange white red, but on that bike as I have mentioned prior, it had so many carb and rotor isssues that after I had my brother rebuild the carbs and pay handsomely, and buy a new customrewind.com rotor for another $100, I did not need to upgrade the ignition at all...


So just to be sure: The '79 bike of Masika which is eating ignitors in the other thread never had to do with these resistors? The resistors were only used for your '81 Custom mods, right?
Cosky's great (free) online manual: http://cosky0.tripod.com

forum links to common technical issues

SchoolDaGeek
Posts: 147
Joined: Fri Aug 26, 2011 8:36 pm

Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby SchoolDaGeek » Wed Jun 19, 2013 7:27 am

You are correct, sir.

Masika's bike ran fine from the beginning, I only replaced the rotor, and the voltage returned to normal during charging, after I got it home and replaced it.

The first two spark units blew under charging load, the last unit blew with the R/R disconnected completely.

The only discrepancy was that the 30amp fuse did blow by me dropping a tool into the battery box or when I was re-connecting the starter solenoid, I cannot remember which it was, but the bike was not in operation/running when it happened.
Buy New, Wire Right. BNWR. LOL

ScottBowl
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Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby ScottBowl » Sun May 25, 2014 8:35 pm

Hello everyone,

I have been trying to make this swap using The dodge voltage regulator and two of the 4-prong standard bridge rectifiers.

The schematics I have to go by are either

A) the old diagram with two rectifiers and ford voltage regulator

B) the new diagram with dodge voltage regulator and one 3-phase rectifier

I was under the impression that the 3-phase rectifier was interchangable with 2 of the standard rectifiers, but I'm having a really hard time understanding what to connect where...

Could anyone please help me?

I may end up just ordering a 3-phase rectifier but it probably won't make it here for a couple weeks, and I don't think I can return the rectifiers I've bought already.

thanks!

dr4
Posts: 11
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Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby dr4 » Sat Oct 18, 2014 4:56 pm

Hello everyone,

Many thanks to everyone for all the input about the HEI ignition upgrade. I was able to successfully build the system and did a 55-mile test drive today. The bike runs incredibly better and smoother. Unfortunately I'm still getting in the 30's on gas mileage which is about where I was before the upgrade, but that's another thread!

I used the diagram straight off the first page of this topic. I found two 4-prong DR100-matched aftermarket modules for $22 on ebay (used), two new aftermarket C849 coils for $26, a set of spark plug wires at Autozone for $17, and about $15 worth of connectors, heat sink compound from Radio Shack, etc.

I did not use the starter circuit with the resistors and diodes for a couple of reasons. This bike has always started well, and I wanted to see if the spark plug gap I used would be a factor in cold starts first. So far no problem at all starting.

I set the pulser to rotor gap at 0.6 mm (.024 in.), and spark plug gap to .060" (D8EA's). I practiced cutting on some old spark plugs to see if I could side-gap them, and wasn't happy with the results, so I left the electrodes as is. Seems to fire just fine.

I cut a heat sink out of 1/8" aluminum, at irregular angles to fit the space from the edge of the battery to just under the frame on the air filter side, as long as I could fit. I'm estimating there's about 15 square inches available for the two modules. I mounted one on top toward the gas tank, and the other on the underside of the heat sink toward the back fender, and it just tucks into the space. I left the stock connectors as is, so if needed the original CDI boxes can be plugged back in without any problem.

There is still a miss and surge under load above about 5500 rpm, but now I know the ignition is not the problem. I'm down to 2 or 3 possibilities there--bad fuel bowl levels, carb slides sticking or weak springs, or possibly cam chain tensioner (broken bolt).

All in all, I would consider the ignition upgrade a success. Many thanks especially to pinhead, loudhvx, and others for making your many hours of experience available to the rest of us.

dr4

dr4
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Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby dr4 » Sat Nov 15, 2014 9:33 pm

Just wanted to update my previous post for the record.

After the upgrade to the GM HEI ignition, I started out getting 44 mpg, then 42, then 40 etc. My last tank was 36 mpg.

Today I pulled the plugs. There was a burn line on the underside of the ground electrode, so I knew what I was dealing with. The spark was following the shortest path to the near edge of the center electrode, which had already begun to carbon up.

I went ahead and got the dremel tool out, did a true side-gap of .060", and got 46.3 mpg on a 62-mile run, mostly 45-55 mph.

The bike still starts fine, even though it's been in the low 30's, so I don't feel the need to add the starting circuit.

All in all, I am very pleased with this upgrade. By the way, I've got two CDI units and 2 stock coils for sale if anybody needs them. You can pm me if interested.

Once again, thanks to all who contributed their experience to this thread.

Loudhvx
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Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby Loudhvx » Tue Dec 30, 2014 10:40 pm

Glad it worked!

Thanks for posting the details, especially on not needing the start booster. It's strange on how some bikes need it and some don't.

Opening the spark gap does improve performance, but puts stress on the entire system. As you could tell, it forced the spark away from the intended location on the plug electrode. It also stresses the coils, igniters, and wires. But as long as those things are new, clean, and dry, it should be ok. Luckily those parts are now cheap and easy to get at most auto parts stores if something should blow up :) .

Trevdawg
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Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby Trevdawg » Sun Mar 05, 2017 1:49 am

All photos are gone and no links work.
What am I to do?!?!


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Hotrodhalfton73
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Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby Hotrodhalfton73 » Fri Jun 09, 2017 9:06 am

I like the hei conversion it sounds like a cool idea but i have read up on it on a bunch of sites and i understand the concept but it seems every time there's directions and diagrams they allways just seem vauge and leave me with questions...im 44 now not new building cars and bikes been to automotive school and built bikes frim ground up all custom fabrication not bolt ons and done beautiful hidden wireing on the bikes all harley tho...that all have simple ignitions. But I am pretty green when comes to electronics, and this conversion seems intimidating... Which is better 4 or 7 pin modules, are people using 7 because there more readily available​ at bone yards so can get them on cheap. Because quality performance ones in jegs/summit are fairly cheap(and im broke all time too)...its great to do things on a shoe string but damn spend alittle money to use real nice components, But when comes to the conversion a idiot proof diagram with lables and explaination leaving nothing left to question. I would love to do this vs struggling to pony up the $500 on a plug n play dyna ign. Or buy pricy oem parts just have a infierior ingnition. Any suggestions. What does not help is the one in the picture on the story looks kike a rats nest...making it seem even more intimidating. Thanks hotrodhalfton

BrokenSpoke
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Joined: Thu Jul 27, 2017 3:51 pm

Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby BrokenSpoke » Sun Aug 06, 2017 1:16 am

I really appreciate the R&D Lou D put into these conversions. I just finished on a 1980 CB650, using a pair of 'Blue' performance 4-pin modules I found on ebay for $26 total and $2 in resistors & diodes from Digikey for a bias supply. Stock ignition coils, measuring at 2.4 ohms each. First time starting, nothing happened! Found I had conveniently left off re-connecting the coil wires after measuring them. Tried cranking with plugs 3 & 4 lying out on top of the head and got spark. Tried starting again, carbs 3 & 4 started dumping fuel out the overflows. Old bike issues...

Advanced the ignition timing and finally it's running! But smoking like crazy, must be all that fuel

Put bike back together, reset timing to where I had marked it. Proceeded to ride around the yard. Now normally if I had tried shifting to 2nd gear around the place, I'd be stalling the bike and going too fast to avoid hitting the garbage cans without pulling the clutch. Today I putted around in 2nd like I was still in 1st and able to roll-on throttle without hesitation. Very nice!

Grabbed the helmet and hit the road. Now the shifter has always been a bit finicky. Any sort of weirdness and it downshifts. That happened about 5 or 7 times. I'm guessing that the ignition is suffering from too much crosstalk. I had not changed the pickup gap, but I did note that a 0.6mm feeler gauge would not fit, it might be the pickups are too close and the voltage levels are just high enough to get the crosstalk acting up. Riding at low RPM's was very smooth and no sudden hiccups into 4th

Parts and sketch based off of Lou D's work:
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Sorting out which wire on pickups is the positive:
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Mapped out the stock connectors that I had chopped off the old modules:
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Map of connectors is viewed from module's point of view. Both connectors have the same pinout, but on one connector the pickup wires are blue while on the other they are yellow. I think this pinout might be the same for all years of the CB650. So if you don't have a 'scope, cross your fingers & try it like I had it

Roughing out a mounting bracket:
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Instead of the silicone grease, I decided to try some of my magic CPU thermal paste. And riveted the 4-pin modules into place because I am that confident about this whole magic business:
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Built the bias supply as a discrete module:
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No tape or heatshrink, just lots of hotglue:
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The more astutely keen-eyed will note I am also doing something else to the bike:
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I took apart the advance, because it squeaked when I turned it by hand. Cleaned, then coated all moving surfaces with silicone damping compound in order to get a less jittery timing

So some more fine-tuning for tomorrow. But so far I am very impressed! Bike went from having a nervous attitude pushing into corners, to getting into and then out of slides halfway through fast corners. Not sure if the top speed improved any, the speedo only goes up to 85. But it sure does seem to get there a whole lot quicker. And smooth!

BrokenSpoke
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Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby BrokenSpoke » Sun Aug 06, 2017 3:56 pm

Just for clarity, I redid the pinout in Deltacad and took a screenshot of that. Assuming you cut off the stock pigtail from the old ignition modules, keeping as much wire as you can. Then this pinout is drawn while holding those wire leads, looking at the rear of the connector. Pinout is identical on both connectors. To make sure there are no mistakes, I would make all connections on one connector to one 4-pin module. There's always a chance of getting the wrong combination of pickup & ignition coil on a module
Image

If you test for battery voltage on the harness side of the module connectors, or at the end of the cut wires while plugged in, you will get battery positive on both the Black & Yellow positions - unless you unplug the coils from the harness. Then you will only get power at the Black

BrokenSpoke
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Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby BrokenSpoke » Sun Aug 06, 2017 4:00 pm

My reference source, used as found without any serious problems
http://geocities.ws/loudgpz/CBheiMod.html

BrokenSpoke
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Joined: Thu Jul 27, 2017 3:51 pm

Re: GM HEI: Cheap and Extremely Effective Ignition Upgrade

Postby BrokenSpoke » Sun Aug 06, 2017 5:15 pm

Just now tried opening up the pickup gap. Using a flat feeler gauge, so it's probably not very exact. But I will continue using that gauge set for further reference. Used the 0.6mm, set until I got a fairly consistent drag across the flats. Downshifting issue is gone, but now there's a dead spot up in the higher RPM's

I suppose, going by how the rumors have it that it's easier to light off a rich mixture & harder to do the same on a lean mix - that possibly I have a lean condition? And maybe also the dwell timing is very low at that point due to increasing the pickup clearance?

Ponderous, time for a beer!


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