1974 distributor question
Thread Starter
Instructor
Joined: Dec 2008
Posts: 116
Likes: 0
1974 distributor question
I have a 74 vette (350). the previous owner had changed from points to electronic ignition. Looking at it closley the other night I noticed that he still had the resistance wire run to the external coil. If the distributor is not recieving the full 12v could this effect the way the car runs? Thanks.
Tech Contributor
Joined: Jun 2004
Posts: 20,847
Likes: 959
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
I have a 74 vette (350). the previous owner had changed from points to electronic ignition. Looking at it closley the other night I noticed that he still had the resistance wire run to the external coil. If the distributor is not recieving the full 12v could this effect the way the car runs? Thanks.
Please read the Ignition sticky, and it will explain why the resistor may still be necessary.
Drifting
Joined: Mar 2011
Posts: 1,886
Likes: 9
The stock coil is not rated for full time 12 volts. Normally, the coil only sees 12 volts while the starter is engaged. As soon as the engine starts, and the starter disengages, the coil is powered through the resistance wire, and only sees maybe 9 volts.
You can buy coils in the aftermarket that are rated for full time 12 volts. Because the initial voltage is a bit higher than stock, these coils will deliver a slightly higher voltage to the plugs. Just add a jumper wire to the coil that is controlled by the ignition switch. And you can then ignore the resistor wire.
These coils are "happiest" when they see the full 12 volts. If the fuse on your jumper wire blows, the car will feel a bit down on power.
You can buy coils in the aftermarket that are rated for full time 12 volts. Because the initial voltage is a bit higher than stock, these coils will deliver a slightly higher voltage to the plugs. Just add a jumper wire to the coil that is controlled by the ignition switch. And you can then ignore the resistor wire.
These coils are "happiest" when they see the full 12 volts. If the fuse on your jumper wire blows, the car will feel a bit down on power.
Last edited by gcusmano74; Mar 12, 2013 at 08:51 PM.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
Different brands/models of those electronic ignition systems are designed to use either the stock voltage feed from the resistance wire OR a direct 12 vdc signal. You will have to query the manufacture of the device you have installed to determine how it should have been wired.
If that device should have received 12 vdc, and you want to keep it, then you need to run a [non-resistance] wire of adequate size from the coil terminal to the point where that resistance wire exits the firewall. Just tap into the resistance wire at that point, then run the regular wire to the coil. You can then cap and wind up the rest of the resistance wire and tie-wrap it somewhere so that you still have it if you ever want to go back to "stock" wiring again.
P.S. While that resistance wire may, in fact, reduce the voltage getting to the coil, its purpose is to limit the current that the coil receives so that it will not overheat/cook. Also, if you do retain that electronic device, the coil you choose should be compatible with it. Likewise, you should have a stock coil, if you keep the resistance wire and stock points system.
If that device should have received 12 vdc, and you want to keep it, then you need to run a [non-resistance] wire of adequate size from the coil terminal to the point where that resistance wire exits the firewall. Just tap into the resistance wire at that point, then run the regular wire to the coil. You can then cap and wind up the rest of the resistance wire and tie-wrap it somewhere so that you still have it if you ever want to go back to "stock" wiring again.
P.S. While that resistance wire may, in fact, reduce the voltage getting to the coil, its purpose is to limit the current that the coil receives so that it will not overheat/cook. Also, if you do retain that electronic device, the coil you choose should be compatible with it. Likewise, you should have a stock coil, if you keep the resistance wire and stock points system.
Last edited by 7T1vette; Mar 13, 2013 at 12:05 AM.
Drifting
Joined: Apr 2007
Posts: 1,970
Likes: 45
From: Cameron Park CA
Absolutely correct! I'm running Lectric Limited One Wire electronic ignition in my '69. The instructions specifically state to use the resistor wire. http://http://www.lectriclimited.com/breakerless_se.htmSo, determine what you have and ask the manufacturer what they recommend.
Pete
Tech Contributor
Joined: Jun 2004
Posts: 20,847
Likes: 959
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
The stock coil is not rated for full time 12 volts. Normally, the coil only sees 12 volts while the starter is engaged. As soon as the engine starts, and the starter disengages, the coil is powered through the resistance wire, and only sees maybe 9 volts.
You can buy coils in the aftermarket that are rated for full time 12 volts. Because the initial voltage is a bit higher than stock, these coils will deliver a slightly higher voltage to the plugs. Just add a jumper wire to the coil that is controlled by the ignition switch. And you can then ignore the resistor wire.
These coils are "happiest" when they see the full 12 volts. If the fuse on your jumper wire blows, the car will feel a bit down on power.
You can buy coils in the aftermarket that are rated for full time 12 volts. Because the initial voltage is a bit higher than stock, these coils will deliver a slightly higher voltage to the plugs. Just add a jumper wire to the coil that is controlled by the ignition switch. And you can then ignore the resistor wire.
These coils are "happiest" when they see the full 12 volts. If the fuse on your jumper wire blows, the car will feel a bit down on power.
My stock 44 year old ignition coil has run for decades with the ballast wire shunted. It's still just as happy as it was the day it left St. Louis.
Please read the ignition sticky.
Instructor
Joined: Sep 2007
Posts: 244
Likes: 3
From: Long Island
Twelve volts is a piece of cake for any stock coil. For heaven sakes, it gets hit with several hundred volts on the primary winding every ignition firing. What the coil doesn't like (or isn't rated for) is high current levels. That's what burns out a coil, not minor stresses like 12 volts.
My stock 44 year old ignition coil has run for decades with the ballast wire shunted. It's still just as happy as it was the day it left St. Louis.
Please read the ignition sticky.
My stock 44 year old ignition coil has run for decades with the ballast wire shunted. It's still just as happy as it was the day it left St. Louis.
Please read the ignition sticky.
Please provide the link to the Ignition sticky as I have seen this referenced for several issues - thanks
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
Tech Contributor
Joined: Jun 2004
Posts: 20,847
Likes: 959
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.