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Username Post: Question for Ignition Man        (Topic#357983)
Ray P W 
Contributor
Posts: 442

Reg: 09-30-15
09-08-19 08:18 PM - Post#2775102    

Do 4-pin module GM HEI distributors require a ground strap like the Standard Motor Products P.N. DR31A?

I ask because both the distributor I've been running for the last 15 years in my street rod roadster and the spare distributor I carry at all times both lack that ground strap. Maybe that's why my coil got toasted this weekend after about 15 years and 24,000 miles.

Also, what's a good source for the carbon rod and spring that goes between the coil and rotor. When I opened the distributor by the side of the road to see why the ignition died I found most of that rod had broken off.

Fortunately, parts cannibalized off the spare distributor got me going again.

Thanks!

Ray W



 


IgnitionMan 
Valued Contributor
Posts: 3645

Reg: 04-15-05
09-09-19 10:49 AM - Post#2775151    
    In response to Ray P W

The two hold down screw holes act as ground for the modules, direct to the distributor body, as does the module metal bottom plate.

When I did a remote module mounting, I always add a separate ground wire from one of the module screws to the engine.

Another important factor is the battery ground cable, negative on the battery to the engine, it is the best "buss bar" we have to ground from.

Low resistance carbon "brush" post is available from many sources, Summit, Jegs, MSD, E-Bay, and should be used on every large coil in cap HEI, from what I feel works best. They are not expensive, and test with normal multi-meter functions. Most are 1.0 ohms or so.

We had resistor plug caps on motorcycles, and the resistors would always go bad, so, we unscrewed the guts and replaced the resistors with properly cut sections of aluminum dowel, put them back together, worked best, but, car HEI is different.

EDIT: More info on grounding.

If you look at the coil mounting in the large HEI, the coil itself has a ground wire coming out of it that fits to one of its hold down screws in the cap. This grounds the coil to the metal coil mounting yoke.

Then, on the other side of the coil mount, there is a steel fitted electrical post, from the bottom of the yoke down to the center terminal hole in the 3 pin connector. This connector goes frm the cap, down to the module area inside the distributor, and this center terminal/wire grounds the coil in the cap to distributor body, and eventually, battery ground.

If the in cap coils are not grounded to the distributor body, no spark will occur.

Conversely, if the in cap coil is replaced with a remote mounted off cap coil, no ground path/wire to it is required.



 
aghaga 
"4th Year" Silver Supporting Member
Posts: 2219
aghaga
Age: 65
Loc: Altavista, Va.
Reg: 07-05-08
09-09-19 12:38 PM - Post#2775157    
    In response to IgnitionMan

As a footnote I got a low resistance carbon post from NAPA, don't remember the number though.




 
Ray P W 
Contributor
Posts: 442

Reg: 09-30-15
09-09-19 01:27 PM - Post#2775161    
    In response to aghaga

Thank you so much Ignition Man and aghaga. On both of the HEI distributors I have there is no connector from the coil yoke to the center terminal hole in the 3-pin connector that connects to the 3 wires going from the cap down to the distributor body. That makes me wonder how the coil was firing. Perhaps it was grounding (sort of) by some other route although I can't imagine what that other route could have been. Oh well. Anyway, I found that connector today on Amazon and placed an order.

Aghaga, I will try NAPA for the carbon post. Here it is:

https://www.napaonline.com/en/p/ECHRR196

Ironically this ignition failure occurred on a local 200 mile street rod "Reliability Run". I was told by the other participants that my roadster did not "fail" because I got it going again with a quick road side repair rather than hooked to a tow truck.

Thanks again guys.

Ray W





Edited by Ray P W on 09-09-19 01:30 PM. Reason for edit: No reason given.

 
IgnitionMan 
Valued Contributor
Posts: 3645

Reg: 04-15-05
09-10-19 08:41 AM - Post#2775241    
    In response to aghaga

On the NAPA brush, did anyone actually ohm the resistance value?



 
65_Impala 
Very Senior Member
Posts: 4247

Reg: 12-29-02
09-10-19 11:05 AM - Post#2775259    
    In response to Ray P W

There was no connection to the middle terminal of the wiring harness inside the cap? I have seen coils with a terminal directly on the black wire instead of a ring that goes to a coil mounting bolt.

If you search you can easily find lots of people who had their HEI work without that grounding strap. But, they typically also suffered from misfire or premature part failures. How well or how long it works without the strap seems to be a total crap shoot.



 
aghaga 
"4th Year" Silver Supporting Member
Posts: 2219
aghaga
Age: 65
Loc: Altavista, Va.
Reg: 07-05-08
09-10-19 11:21 AM - Post#2775260    
    In response to IgnitionMan

I ohm check the one I bought. Don't remember the number but it was about 1/2 of all the others that I had. I do not remember the part number but I recall it being classified as a low resistance.



 
Ray P W 
Contributor
Posts: 442

Reg: 09-30-15
09-10-19 12:06 PM - Post#2775263    
    In response to aghaga

"If you search you can easily find lots of people who had their HEI work without that grounding strap. But, they typically also suffered from misfire or premature part failures. How well or how long it works without the strap seems to be a total crap shoot."

Yes. Just this morning I saw on a Corvette forum a thread where a guy with no grounding strap was having repeated HEI component failures. Other forum members pointed out to him that strap is necessary. So he searched around his shop and found that the grounding strap was once on his distributor but had fallen out when he had the distributor apart in the past.

In my case, I'm a newcomer to GM HEI ignitions and both the distributors I started with in doing my project were lacking the strap. So I simply had no idea they even exist until the last couple of days. I feel really lucky that in the 15 years and 24,000 miles that I've been driving this street rod the ignition didn't fail until last Saturday. I found a safe spot to pull over, it was daytime so I didn't have to fumble around by flashlight light, I had the necessary parts and tools to make a roadside repair and my wife didn't complain at all.

I've already got a couple of those straps ordered on Amazon (one for the distributor on the engine and one for the spare) and they'll be here tomorrow.

Thanks so much for your interest and help guys.

Ray W



 
IgnitionMan 
Valued Contributor
Posts: 3645

Reg: 04-15-05
09-10-19 07:43 PM - Post#2775296    
    In response to Ray P W

I've never seen one that did work without the ground bar and wire. Does the coil have the small ground wire coming out of the coil to the yoke bolt?

I don't get into the after market HEI "performance" coils, as I have found that all of them are worse than a good quality stock coil, and with them, it is only a matter of time before trouble sets in.

Summit and Jeg's usually show parts from all sorts of angles, I'll go take a look at some of them.

Also, to run that small ground wire back through the negative (TACH) wire would not work, it would compromise the coil and stop the spark output. TACH is the coil trigger, grounding it, or the coil to it, stops spark.



 
Ray P W 
Contributor
Posts: 442

Reg: 09-30-15
09-11-19 07:32 AM - Post#2775332    
    In response to IgnitionMan


"I've never seen one that did work without the ground bar and wire. Does the coil have the small ground wire coming out of the coil to the yoke bolt?

Ignition Man,

I have 2 of these distributors. Both of them have a short black wire exiting the coil with a terminal that one of the yoke mounting screws goes through. That grounds the coil to the yoke. But there is no conductor on either of the distributors that connects the yoke to the ground wire coming from the distributor base.

I didn't give this any thought until a couple of days ago when my engine quit because I toasted the brush between the coil and rotor. I sent photos of these parts to the email address I have for you from years ago when we were talking about your water well. Did you get that email?

Ray W





 
IgnitionMan 
Valued Contributor
Posts: 3645

Reg: 04-15-05
09-11-19 09:30 AM - Post#2775339    
    In response to Ray P W

No, sir, I did not. direct contact for me is info.davessmallbodyheis@gmail.com

It has been a common problem with many replacement large HEI rotors that they arc through their plastics, directly to the center shaft, right through the rotor.

When this occurs, the coil is over worked to begin the failure process, with possible multiple module failures until the coil failing is found.

Also, arcing can take the carbon brush out, not as common, but it does occur.

Interesting about the lack of a grounding buss bar. I wonder what would happen adding a ground path, if a jury rigged ground wire from one of the coil hold down bolts, out the cap, to an alligator clip to the distributor body/vacuum advance would work? Would it make a difference, or not??



 
Ray P W 
Contributor
Posts: 442

Reg: 09-30-15
09-11-19 12:14 PM - Post#2775347    
    In response to IgnitionMan

"No, sir, I did not. direct contact for me is info.davessmallbodyheis@gmail.com"

Dave, I just sent the photos to your email address.

"It has been a common problem with many replacement large HEI rotors that they arc through their plastics, directly to the center shaft, right through the rotor."

One of the photos is of the arcing pattern on the inside of the cap.

"When this occurs, the coil is over worked to begin the failure process, with possible multiple module failures until the coil failing is found."

Until this failure last Saturday the module, and all the other distributor components, have been working for about 15 years and 24,000 miles if that fact sheds any light on what triggered the failure.

"Also, arcing can take the carbon brush out, not as common, but it does occur."

There is also a photo of the brush. It looks like it got VERY hot.

"Interesting about the lack of a grounding buss bar. I wonder what would happen adding a ground path, if a jury rigged ground wire from one of the coil hold down bolts, out the cap, to an alligator clip to the distributor body/vacuum advance would work? Would it make a difference, or not??"

The grounding straps I bought are coming in today's mail and I'll install one then run the roadster and see what happens. I'm a geologist, not an electrical engineer, but now that I look at this situation it's a mystery to me how it worked without the coil ground.

Thank you again so much for helping me.

Ray W



 
IgnitionMan 
Valued Contributor
Posts: 3645

Reg: 04-15-05
09-11-19 03:52 PM - Post#2775356    
    In response to Ray P W

As I said in the email, just posting here, the carbon brush can be installed incorrectly.

There is a metal ring on the brush, and a spring on one end. The brush goes into the cap first, with the spring twords the ignition coil, then, the spring protrudes through the insulator.

The insulator holds the brush down. If the brush is installed ABOVE the insulator, there will be a large gap between the brush and commutator on the rotor, and serious coil, and parts melting problems will occur.



 
Ray P W 
Contributor
Posts: 442

Reg: 09-30-15
09-13-19 03:12 PM - Post#2775472    
    In response to IgnitionMan

Ignition Man,

Happy Friday the 13th. I sent this question to your email and also here in case others may have the same question and can benefit from your answer.

Because the button melt down toasted my distributor cap I bought a new Napa/Echlin cap and it came to me with a new button, round insulator and what appears to be a tiny tube of silicone grease. I was very glad to find a made in USA cap in this era of low quality junk from China.

The grease container has first aid instructions but no instructions on where to apply the grease. Can you please tell me where to apply the grease? The amount looks very small, like just enough for the brush but I want to do this properly.



 
IgnitionMan 
Valued Contributor
Posts: 3645

Reg: 04-15-05
09-13-19 07:12 PM - Post#2775481    
    In response to Ray P W

Don't get the grease in your eyes.

To set the button and insulator up, in the bare cap, set the bushing, spring end up.

Then, lube both sides of the insulator with the grease.

Set insulator over the spring, spring through insulator, insulator against cap.

Install ground buss bar and coil, done.



 


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