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djdavis75
Tribal Scout

USA
17 Posts

Posted - 29 Jan 2012 :  11:27:05 PM  Show Profile  Reply with Quote
My dad had sold his 1968 Firebird and then bought it back several years later. The other owner had replaced the original ignition with a HEI. After a recent engine rebuild we replaced the failing HEI with a MSD Ready To Run distributor using the same factory wiring to power it.

Since the ignition upgrade we've been having trouble with the car idling with the headlights on. So today I decided to check the voltage at the coil and it was about 12.4 volts with the key on, engine off. With the engine idling, it dropped to 11.8 volts. Once the headlights were turned on, it dropped below 10 volts, and the car began to die as usual. I checked the voltage at the battery with it idling and it had 14.2 volts. So we're getting over 2 volts drop at the coil. So I assume the factory wire we're using is a resistor wire.

So I've read many posts and articles about converting from the factory points ignition to a modern electronic one. I'm a little confused. Some people say just bypass the factory wire at the firewall, some say hook to the fuse box, some say run straight off the ignition switch.

My question is, what's the best, most reliable, and safest way on a 1968 Firebird to get full power to the new ignition system.

Any help would be greatly appreciated.


1968 Firebird
400 Stroker (461 CI)
10.0:1 Compression
Performer RPM Heads
Comp Cams Magnum 280H
Performer RPM Intake
Performer 750 CFM (1407)
MSD Pro Billet Read-To-Run/Blaster 2 Coil
Doug's Headers


Edited by - djdavis75 on 29 Jan 2012 11:38:04 PM

mike mcarthur
Pony that Jumps

USA
2475 Posts

Posted - 30 Jan 2012 :  08:04:59 AM  Show Profile  Visit mike mcarthur's Homepage  Reply with Quote
The headlights coming on should not affect the voltage to the coil if you are showing 14 at the battery. If you check the voltage at the lights you will likely read the same thing low voltage. I think you have some ground issues somewhere. Check, clean and make sure all grounds are good. There are a bunch of them.

It's the stuff you learn after you know it all that's important
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Blued and Painted
Chief PONTIAC

USA
3404 Posts

Posted - 30 Jan 2012 :  10:52:38 AM  Show Profile  Reply with Quote
I once tried to run a HEI on the same circut with an electric w/pump and fuel pump. Even with heavy guage wire the vehical (old blue) would bearly run. So i ran a dedicated switched circut and hade no more problems. HEI's do like the full 14v. AND what Mike sayed about body and fraim grounds. The body will not ground through the engine mounts. Alternators dont put out much at idle but still should not drop below 12v. The battery should carry you through the low output time. Bad batteries can cause many problems. Good luck with the Old Bird.


Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.
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djdavis75
Tribal Scout

USA
17 Posts

Posted - 30 Jan 2012 :  11:18:24 AM  Show Profile  Reply with Quote
I never checked the battery voltage with the lights on. With lights off, at idle, battery was around 14.2 volts, coil voltage was about 11.8 volts. I checked everything with a digital volt meter. I checked the the battery from hot to negative post. I checked the coil with the red lead on the coil + terminal and the black lead directly to the batteries negative post.

The entire MSD setup is grounded via the supplied wire to the intake manifold. The large ground cable from the battery is connected to the passenger side head. The small ground from the battery is connected to the passenger side fender I believe.

1968 Firebird
400 Stroker (461 CI)
10.0:1 Compression
Performer RPM Heads
Comp Cams Magnum 280H
Performer RPM Intake
Performer 750 CFM (1407)
MSD Pro Billet Read-To-Run/Blaster 2 Coil
Doug's Headers

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Blued and Painted
Chief PONTIAC

USA
3404 Posts

Posted - 30 Jan 2012 :  11:32:41 AM  Show Profile  Reply with Quote
I must have missed the MSD part. Calling all SBC I mean MSD Guys.


Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.
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dgray
Cochise

845 Posts

Posted - 30 Jan 2012 :  3:19:47 PM  Show Profile  Reply with Quote
I was having trouble on my '66 until I upgraded to a 100 amp alternator. My original was only rated 60 amp on a good day and the voltage would drop to 11.8 -12.1 at idle which is not enough to keep everything happy. The old points ignition runs at about 9 volts but even Pertronic needs a full 12 volts or more. I was told that the resistor wire was to protect the orginal ignition coil.
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mike mcarthur
Pony that Jumps

USA
2475 Posts

Posted - 30 Jan 2012 :  5:23:15 PM  Show Profile  Visit mike mcarthur's Homepage  Reply with Quote
The resistor wire was there to protect the points from burning up prematurely, The points control the voltage build up in the coil.

It's the stuff you learn after you know it all that's important
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djdavis75
Tribal Scout

USA
17 Posts

Posted - 31 Jan 2012 :  1:57:55 PM  Show Profile  Reply with Quote
Can anyone who has done a HEI conversion or installed an electronic ignition on a first gen Firebird tell me how they ran the 12 volt supply to the distributor?

That is what I've read also, about the resistor wire being to protect the points. I thought the resistor wire had been removed because the HEI had been installed. Apparently none of the electronics ignitions on this car have been getting the correct voltage.

Dgray, we've thought about upgrading to a larger alternator also.

1968 Firebird
400 Stroker (461 CI)
10.0:1 Compression
Performer RPM Heads
Comp Cams Magnum 280H
Performer RPM Intake
Performer 750 CFM (1407)
MSD Pro Billet Read-To-Run/Blaster 2 Coil
Doug's Headers

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cortcomp
Coyote

USA
5335 Posts

Posted - 31 Jan 2012 :  2:23:46 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
It's usually any kind of key-switched fused source. Aftermarket harnesses have their own 12v ignition supply. You could trace that wire back and remove it and install normal wire and it should be fine, or you can tap off of a key-on circuit, install an inline fuse, and go from there. You could run from the battery/alt and through the key switch, etc.

key points you want are key switched and no resistor wire. How you do it is up to you. Fused is of course always a good idea.
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Blued and Painted
Chief PONTIAC

USA
3404 Posts

Posted - 01 Feb 2012 :  12:23:21 PM  Show Profile  Reply with Quote
Just found good instructions in the Technical Articles section on the Home Page. Boom!


Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.
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djdavis75
Tribal Scout

USA
17 Posts

Posted - 06 Feb 2012 :  10:42:52 PM  Show Profile  Reply with Quote
I had read the instructions in the Technical Articles section also, good info. Just didn't want to start splicing into wires under the dash unless absolutely necessary.

I decided to pull the large wiring harness plug off the firewall. I traced down the resistor wire, and removed the terminal it was connected to from the plugin. I then got the resistor wire off the terminal, and had a friend solder a good copper wire to the terminal. I then put it back in the plugin and hooked it back up. Taped the wire into the harness so it looks nice. I ran out of daylight and had to call it a day. So I'll finish up next chance I get and see if it works.

1968 Firebird
400 Stroker (461 CI)
10.0:1 Compression
Performer RPM Heads
Comp Cams Magnum 280H
Performer RPM Intake
Performer 750 CFM (1407)
MSD Pro Billet Read-To-Run/Blaster 2 Coil
Doug's Headers

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djdavis75
Tribal Scout

USA
17 Posts

Posted - 12 Feb 2012 :  10:51:42 PM  Show Profile  Reply with Quote
Got another chance to mess with the Firebird a few days ago. Checked and the wire had full 12+ volts with key on and while cranking. So I did away with the wire from the starter. Car starts and runs fine now. All problems we were having seem to be solved.

1968 Firebird
400 Stroker (461 CI)
10.0:1 Compression
Performer RPM Heads
Comp Cams Magnum 280H
Performer RPM Intake
Performer 750 CFM (1407)
MSD Pro Billet Read-To-Run/Blaster 2 Coil
Doug's Headers

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cortcomp
Coyote

USA
5335 Posts

Posted - 13 Feb 2012 :  08:23:26 AM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
Excellent! I love hearing of problems that have easy fixes. It gives me hope that every little issue i run into won't always mean the motor has to come out :)
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Total Jackass
Tribal Scout

0 Posts

Posted - 14 Jan 2014 :  04:24:33 AM  Show Profile  Reply with Quote
Q. When is a car not a car?
http://www.kinddress.com/robe-de-marie-empire.html

I'm a first class jerk and don't you forget it!
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Phil
The Great White Buffalo

USA
7214 Posts

Posted - 14 Jan 2014 :  6:31:42 PM  Show Profile  Reply with Quote
TTT

Bowties are for Pee-wee Herman. "Chevy": even the name sounds cheap, but not as cheap as your Pontiac will be with an LS transplant.
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