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Old 09-13-2017, 01:42 PM   #26
RichardJ
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Re: HEI issues?

from above
>>If the resistance wire from the ignition switch to the distributor is still being used then he won't have 12v. Likely nearer 7v which causes undue heat in the module.<<

Absolutely and completely false.

To begin, you should be starting with 14Volts, not 12v, assuming you have a working alternator.
That dreaded ballast or ignition resistor wire measures 1.6 Ohms. (1.8 ohms on the inline six)
If you would insert an Ammeter in the B+ wire feeding YOUR HEI, if it is an original GM HEI, you will measure 1-2 AMPS. GM actually list it as 2 Amps in some spec sheets and sometimes 1.5 Amps.

OHm's Law states; Voltage = Current x Resistance

This will give you Voltage drop across the Resistance Wire. I.E. the voltage you are fearfull of losing from the 14Volt supply voltage.

The dreaded 1.6 ohms X GM's 2 Amps = 3.2 Volts dropped across the resistance wire. MAX

14 Volts - 3.2 Volts = 10.8 Volts at the HEI BAT terminal.

In reality the stock HEI with stock coil will draw less than 2 Amps and through an original resistance wire you will still have between 11 and 12 volts at the HEI Bat terminal.

It is also true that the stock HEI when supplied with anything from 8-16 Volts will still supply adequate secondary voltage from idle to 6,000 rpm.

A points ignition and a HEI ignition are both called Induction Ignition systems.

You need to understand that the 10V or 12V or even 14V flowing through the ignition coil does not generate the secondary voltage that fires the spark plug.
12volts flowing through a primary winding of the ignition coil generates a magnetic field around the primary and secondary windings.
It isn't the 12Volt generated magnetic field that causes current to flow through the secondary winding to the plugs.

IT"S WHEN YOU REMOVE THE 12 VOLTS.

When the points open and the 12 volts stops pushing current through the coil, The magnetic field COLLAPSES. When the magnetic field collapses. it generates as much as 300 Volts across the primary winding. This voltage is called Back EMF.
Coil advertisements often include information such as a winding ratio of 100:1

300 primary volts X 100 = 30,000 secondary volts, potentially. When the 20k-30k is being generated in the secondary winding, you do not have 12 volts on the primary winding, you have 200-300 Volts.

That arcing you see across the points on a points ignition isn't the 12 volts, it's the 200-300 volts looking for a place to go. Most of it goes into the condenser and later discharged when the points close again.

The points ignition can't maintain dwell time as rpm increases. The magnetic field doesn't have enough time to be fully saturated and the 300 volt number drops.

The point closed is the Dwell time and is mechanically linked to the points open time by the shape of the lobe.
That's where the HEI comes in. It can control dwell time at higher rpm.

If you don't understand any of that above, you should stop expounding the crap about having to have a FULL 12VOLTS for the HEI.
If you're going racing that's a different story. You should know that there are circletrack racers out there that run a racing HEI without an alternator. Starting a race with 12.5 battery voltage, they still have plenty of high rpm ignition, 40 laps later when the Bat may have dropped below 10 volts.

For the street, I can tell you I installed a coil-in-cap HEI in my truck more that 25 years ago. 10 years ago when I installed the AC, I switched it to an external coil HEI. The original Resistor Wire is still in place. I read 11 Volts at the distributor. The truck gets 15-16 mpg on the highway and it can run 70-75 mph for a couple hours at a time and never skip a beat.
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Old 09-13-2017, 02:06 PM   #27
GASoline71
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Re: HEI issues?

Quote:
Originally Posted by zachste View Post
Just for clarification's sake, we are talking about the ICM correct? Like this https://www.summitracing.com/parts/sum-850100/overview/

That's the one!


Quote:
Originally Posted by RichardJ View Post
If you don't understand any of that above, you should stop expounding the crap about having to have a FULL 12VOLTS for the HEI.
If you're going racing that's a different story. You should know that there are circletrack racers out there that run a racing HEI without an alternator. Starting a race with 12.5 battery voltage, they still have plenty of high rpm ignition, 40 laps later when the Bat may have dropped below 10 volts.

For the street, I can tell you I installed a coil-in-cap HEI in my truck more that 25 years ago. 10 years ago when I installed the AC, I switched it to an external coil HEI. The original Resistor Wire is still in place. I read 11 Volts at the distributor. The truck gets 15-16 mpg on the highway and it can run 70-75 mph for a couple hours at a time and never skip a beat.
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Old 09-13-2017, 02:47 PM   #28
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Re: HEI issues?

Quote:
Originally Posted by RichardJ View Post
from above
>>If the resistance wire from the ignition switch to the distributor is still being used then he won't have 12v. Likely nearer 7v which causes undue heat in the module.<<

Absolutely and completely false.

To begin, you should be starting with 14Volts, not 12v, assuming you have a working alternator.
That dreaded ballast or ignition resistor wire measures 1.6 Ohms. (1.8 ohms on the inline six)
If you would insert an Ammeter in the B+ wire feeding YOUR HEI, if it is an original GM HEI, you will measure 1-2 AMPS. GM actually list it as 2 Amps in some spec sheets and sometimes 1.5 Amps.

OHm's Law states; Voltage = Current x Resistance

This will give you Voltage drop across the Resistance Wire. I.E. the voltage you are fearfull of losing from the 14Volt supply voltage.

The dreaded 1.6 ohms X GM's 2 Amps = 3.2 Volts dropped across the resistance wire. MAX

14 Volts - 3.2 Volts = 10.8 Volts at the HEI BAT terminal.

In reality the stock HEI with stock coil will draw less than 2 Amps and through an original resistance wire you will still have between 11 and 12 volts at the HEI Bat terminal.

It is also true that the stock HEI when supplied with anything from 8-16 Volts will still supply adequate secondary voltage from idle to 6,000 rpm.

A points ignition and a HEI ignition are both called Induction Ignition systems.

You need to understand that the 10V or 12V or even 14V flowing through the ignition coil does not generate the secondary voltage that fires the spark plug.
12volts flowing through a primary winding of the ignition coil generates a magnetic field around the primary and secondary windings.
It isn't the 12Volt generated magnetic field that causes current to flow through the secondary winding to the plugs.

IT"S WHEN YOU REMOVE THE 12 VOLTS.

When the points open and the 12 volts stops pushing current through the coil, The magnetic field COLLAPSES. When the magnetic field collapses. it generates as much as 300 Volts across the primary winding. This voltage is called Back EMF.
Coil advertisements often include information such as a winding ratio of 100:1

300 primary volts X 100 = 30,000 secondary volts, potentially. When the 20k-30k is being generated in the secondary winding, you do not have 12 volts on the primary winding, you have 200-300 Volts.

That arcing you see across the points on a points ignition isn't the 12 volts, it's the 200-300 volts looking for a place to go. Most of it goes into the condenser and later discharged when the points close again.

The points ignition can't maintain dwell time as rpm increases. The magnetic field doesn't have enough time to be fully saturated and the 300 volt number drops.

The point closed is the Dwell time and is mechanically linked to the points open time by the shape of the lobe.
That's where the HEI comes in. It can control dwell time at higher rpm.

If you don't understand any of that above, you should stop expounding the crap about having to have a FULL 12VOLTS for the HEI.
If you're going racing that's a different story. You should know that there are circletrack racers out there that run a racing HEI without an alternator. Starting a race with 12.5 battery voltage, they still have plenty of high rpm ignition, 40 laps later when the Bat may have dropped below 10 volts.

For the street, I can tell you I installed a coil-in-cap HEI in my truck more that 25 years ago. 10 years ago when I installed the AC, I switched it to an external coil HEI. The original Resistor Wire is still in place. I read 11 Volts at the distributor. The truck gets 15-16 mpg on the highway and it can run 70-75 mph for a couple hours at a time and never skip a beat.
Well stated Richard. I doubt that too many beside you and I understand the technical aspects, or will be able to convince many others.

The level of exasperation you exhibit equals my own when it comes to posters who forget to give details even as simple as the year of their trucks.

Points to add.
You are correct about the 12 volts not generating the 20K to 30K volts on the induction side of the coil. I believe the boost comes from the discharge through the condenser (points), or the ignition module (HEI) what say you?

You didn't address the module heat caused by low voltage but I think this is in error and the heat is caused by the engine temperature transferred through the distributor so an insulator is used. Resistance also produces heat so it may need to transfer to the distributor so either theory is possible.

It has been stated that using the external voltage regulator, which generates voltage spikes, is often the module killer in HEI ignitions since the modules do not like voltage spikes. Most digital equipment follows that rule.

Your last paragraph bears out the original post where he states that his engine ran fine until it died and again after he got it restarted.


I'm open for discussion.
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Old 09-13-2017, 07:45 PM   #29
'68OrangeSunshine
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Re: HEI issues?

Quote:
Originally Posted by zachste View Post
You're saying the blue is the power wire? I thought it was power wire in back, tach in the front. After pulling it out from the connector, tried putting it back in and crimping. It actually fired right up, like a dummy I tried the multi meter while running and it died as soon as I grounded it. Started back up, but tried to rev it a tiny bit and it cut out and died. Started back up though. I seem to be causing more problems for myself here. Wiring tends to be out of my wheel house. Unless it's just a bad connection on the batt side.
Good catch. OK you got me, I was just shooting from memory, I should've double checked. Looking at RichardJ's post #22, the correct orientation is shown.

But intermittent on the Tach line shouldn't have affected ignition. That's what threw me off.
By ''wheel house'' do you mean the engine bay, at the bulkhead terminal block? Or the cab. [Kind of a salty nautical handle for a truck cab if it is. lol]

I'm referring to pulling a tap off the inside-cab fuse block. Just easier to get to.

Yes, a female terminal taps into a recessed positive terminal in the fuse block.

Without getting obsessively technical-- the 20 ga. Orange/White/Purple wire coming out of the bulkhead connector on the drivers side firewall, feeds nominal 12 VDC at start, then, being a resistance wire, increases resistance as it heats up and cuts down to 9 - 7 VDC, to keep from burning up the points. HEI modules fed voltages under 12 VDC heat up and fail. At the other end of the resistance wire it splits into two 20 ga Yellow lines, one to the Coil positive terminal and the other to the starter. No longer needed in the HEI system.
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Last edited by '68OrangeSunshine; 09-13-2017 at 08:03 PM.
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Old 09-13-2017, 08:23 PM   #30
zachste
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Re: HEI issues?

Quote:
Originally Posted by '68OrangeSunshine View Post
Good catch. OK you got me, I was just shooting from memory, I should've double checked.
But intermittent on the Tach line shouldn't have affected ignition. That's what threw me off.
By ''wheel house'' do you mean the engine bay, at the bulkhead terminal block?
I'm referring to pulling a tap off the inside-cab fuse block. Just easier to get to.
By out of my wheel house I meant out of my comfort zone doing electrical stuff. More comfortable doing suspension, body/paint work, those kinds of things.

So I checked, that black Batt power wire already runs to the fuse block.

Would pushing that multi meter almost through that power wire possibly cause new issues? The truck started again, but sounds like it's trying to suck too much air when you tap the throttle, to the point if you press it too hard it will stall out. Seems to idle alright for a bit though. I have a video but have to get it uploaded since the photobucket BS.
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Old 09-13-2017, 08:30 PM   #31
zachste
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Re: HEI issues?

https://flic.kr/p/YGxnqR
Here's a link to the video couldn't get it to embed.
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Old 09-13-2017, 09:01 PM   #32
Myoldtruck
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Re: HEI issues?

I did the Hei conversion on my 350 a few months ago. I used the old resistor wire as a 12v + trigger for a 30amp relay on the fire wall. I ran a dedicated 12gauge wire from a spare fuse box I installed in the cab to power up the contact side of the relay, then over to the Hei.
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Old 09-13-2017, 09:19 PM   #33
zachste
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Re: HEI issues?

Another longer version. It didn't start doing this until last night/today. So that's why I feel like this may be something I caused possibly?
https://flic.kr/p/XsABzr
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Old 09-14-2017, 01:44 AM   #34
toolboxchev
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Re: HEI issues?

The way that engine backfires and chuckles along seeing the carb fumes coming back out makes me think the timing is Way Off.

But to check it you have to get it idling. Do you know how to set your timing working it backwards? Or all in by 3000 rpm?
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Old 09-14-2017, 09:03 AM   #35
zachste
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Re: HEI issues?

Quote:
Originally Posted by toolboxchev View Post
The way that engine backfires and chuckles along seeing the carb fumes coming back out makes me think the timing is Way Off.

But to check it you have to get it idling. Do you know how to set your timing working it backwards? Or all in by 3000 rpm?
Which would make me curious how the timing could be so far out. I don't know how to set the timing working it backwards. At this point I think it's going to my buddy's shop to get sorted, as I just simply don't have time to keep chasing this. As hard as it is to "diagnose" on the forums, thanks for all the tips so far guys!

Last edited by zachste; 09-14-2017 at 09:42 AM.
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