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The resistor (either ballast or resistance wire) heats up it decreases the voltage to the points... open or closed and it doesn't matter what the dwell is.
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Originally Posted by Willcox Corvette
I'll make this my last post... The facts are simple and easy to understand. I agree. That's why I don't understand the need for the corrections below.
The resistor (either ballast or resistance wire) heats up it decreases the voltage to the points... open or closed and it doesn't matter what the dwell is. The laws of Physics, along with Ohm's Law, disagrees. When the points are open, there's no current. At that point the ballast is just that: dead weight. Also, the reason that the ballast resistance was converted from a small winding into a long wire (other than possibly cost) is that a long resistance wire doesn't get as hot as a small compact resistor. The purpose of the ballast is to include resistance into the primary circuit to limit the primary current, not for any voltage issues. It is not there to heat up and increase the resistance. Anytime an electrical device heats up it diminishes the reliability and lifespan of the part. Ballast wires, by design and simple physics, are much more reliable than ballast (wire wound) resistors.
The OP never stated they didn't have the resistance wire (it was my speculation). Re-read OP post #9.
During the 30 degree's of dwell what is the voltage to the points.. that would depend on the resistance caused by the wire serving the points either through a ballast resistor or a resistance wire.
If you bypass the resistor then the voltage would be 12.. No, that violates Ohm's Law. The voltage across the points is near zero, as the points are a direct short circuit. You are forgetting that the coil is upstream of the points, and it (along with any ballast) will drop the voltage (V=IR).
Right after the points open.. the voltage would be what ever is deemed by the ballast resistor.. (or resistance wire) No, the voltage would be 150-200 volts, due to the magnetic field in the coil collapsing (and also regardless of the presence of a ballast resistance).
There is a pattern.. the voltage to the points would be determined by either the ballast resistor or the resistance wire... The ballast resistor or the resistance wire dictates the voltage. No.
The OP's car never had a ballast resistor, it has a resistance wire Makes no difference for this discussion. and it was my speculation that someone cut it out the resistance wire and replaced it with standard wire that is causing the issue, but that was pure speculation. The OP's car originally had a resistance wire that dropped the voltage to the points when the wire heated up and if it is still present is a question that has not been answered. This same resistance wire determines the voltage to the points... A resistor limits the current through a circuit. It is NOT a voltage regulator. And a periodic constantly changing voltage drop through a resistance is not a regulator either. The only regulation in the system is the alternator voltage regulator.
I don't care about when the points are open or closed.. or what the dwell is, the fact is that the voltage to the points has to drop to prevent premature failure. Voltage is not the problem. It is the current going through the points that burn them up. The ballast limits the (peak) current, not the (peak) voltage that the coil and points have to contend with.
Obviously GM had a good plan in place that worked for years and it didn't include running 12 volts continuous to the points. The fact is that all cars 1955-1974 had a drop on voltage after start up, and this was by design to keep from burning points out. See below.
I'm sure GM had a few good electrical engineers in place when they developed this system... and I am 100 percent positive that you can not run straight 12 volts to a pointed distributor without risking failure of the points. I 100% disagree. As long as you have sufficient resistance in the primary circuit to keep the amperage reasonable (generally less than 4 amps, it seems) there isn't a problem. And whether the resistance is in the form of a ballast, or in the coil primary winding itself, it makes no difference to the points.
Willcox
Here's how the old points systems work. In 1955 when GM converted from 6v to 12v systems, they had to make a lot of changes to the cars' electrical system and components to keep from frying everything in the car. They had two options. They could change the necessary electrical parts (such as headlights, by increasing the filament resistance to maintain the same filament wattage to retain the same luminosity), or just add a resistance in series to the part, to retain the same current through the part even though the system (generator/alternator) voltage doubled. As an ignition coil doesn't care what the voltage across it is (the energy stored in a coil is dependent on the current through it, not the voltage across it) someone in the electrical group figured out that if they just added a current limiting resistor (ballast resistance) before the coil they can continue using the same design coils in a 12v car as they had in the 6v cars. The same potential savings applied to other pieces in the ignition system too (points, condenser, etc), meaning less parts that need to be redesigned and tested before production.
Now, things worked quite well for many years (during normal operation). However, after just a couple years it was noticed that this simple setup wasn't optimal on frigid winter mornings. During cold cranking times, the battery voltage obviously dropped, not only from its reduced chemical efficiency when cold, but also due to all the cranking/starter motor current consumed turning over a cold engine with thick syrupy oil. The low battery voltage was often insufficient to push enough current through the ballast resistor and ignition coil to get sufficient energy into the coil to light off the fuel drenched plugs. Big customer satisfaction problem there. One solution is to re-engineer the ignition coil to get more energy out at lower primary currents (downside: lotsa engineering, testing, and manufacturing time and money), or come up with a more clever alternative. A bright individual (or individuals) came up with a brilliant, incredibly low cost way of rectifying the problem. Given that the ballast resistor was the main problem (restricting current to the coil when the battery voltage was low), and this issue is only a problem when the engine is cranking over, was there a way to "get rid of" the ballast resistor during cranking. The result was the starter solenoid shunt wire that bypassed the ballast during cranking (IIRC, first implemented about 1958). While it's often stated that this circuit is there to provide "straight 12 volts" to the coil during cranking, it's actually there to provide normal coil primary current levels to the coil despite the battery being down at 6-10 volts. The down side of this clever circuit is that it will burn out the points due to excessive current when the engine is cranked over for long periods when the battery voltage isn't dragged down (ie: warm weather).
Last edited by 69427; Aug 4, 2016 at 05:44 PM.
Reason: Added content.
I am interested in tackling this conversion but have questions. Keep in mind not an experienced mechanic :-)
* does the distributor have to come out to do this or can i get to everything with it still on the car ? Im afraid to pull distributor for fear of not getting it back in right position
* does this conversion mean changing anything about the timing ? Is there any other dialing in to do ?
I am interested in tackling this conversion but have questions. Keep in mind not an experienced mechanic :-)
* does the distributor have to come out to do this or can i get to everything with it still on the car ? Im afraid to pull distributor for fear of not getting it back in right position
* does this conversion mean changing anything about the timing ? Is there any other dialing in to do ?
No you don't need to pull the distributor. I installed a Pertronix Ignition.
Just hand tools As I recall there is a feeler gauge that comes with the kit.
to set it up. Installation time is not much different than just replacing the points & Condenser. Easy job! Great improvement! Good luck.
You just need to know whether the electronic system you are installing is to use the power coming from the resistance wire on your car or if it should be fed with direct 12 vdc (with no ballast resistor). Follow installation instructions and you should be fine.
I have a 69 with a 71 LS-5 454. The first time I had an issue with points, I replaced the distributor with a MSD with mechanical tach drive, paired with a MSD 6AL ignition system. I've had it for almost 8 years, and the only time I've touched it after initial set up, was when I pulled it out to rebuild my motor. And it makes the tach needle steady.
You guys can argue between yourselves til you blue in the face. I've used this system on a few race cars, and a few daily driven street cars. Somebody a few pages back said they'd never buy another one because of the bang for the buck. When I don't have any ignition issues for years, that's worth the money to me.
Is that because this varies from model year to model year ? If so my car is a 74 with an L48 base engine.
If not a model year thing - why would this not be a consistent thing for all C3s?
Originally Posted by 7T1vette
You just need to know whether the electronic system you are installing is to use the power coming from the resistance wire on your car or if it should be fed with direct 12 vdc (with no ballast resistor). Follow installation instructions and you should be fine.
no offense to anyone, but why hasn't it been brought up that the condenser could be bad? they do go bad. they can be tested. sometimes the wire is incorrectly hooked up or damaged. sometimes the wrong one is installed. the condenser acts as sort of a cushion to keep the points from burning. that is the first thing I would check. Then the grounds. bad grounds can kill the condenser.
then the point cam/point gap. worn cams can cause issues as well. finally, what brand points? cheap Chinese junk or good quality stuff? we see this all the time with older vehicles and bikes, a lot of the replacement ignition stuff is extremely poor quality these days...
I am interested in tackling this conversion but have questions. Keep in mind not an experienced mechanic :-)
* does the distributor have to come out to do this or can i get to everything with it still on the car ? Im afraid to pull distributor for fear of not getting it back in right position
* does this conversion mean changing anything about the timing ? Is there any other dialing in to do ?
I installed the Breakerless SE system in my Corvette and have been very happy with it. Breakerless SE is the simplest of all the conversion systems as no additional wires need to be run. You basically unscrew your points and and screw down the electronic module in their place. The complete installation takes about 15 minutes. You do not need to pull your distributor You should always check the timing after making any changes to the distributor or ignition system. The installation instructions are available online so you can review how easy the conversion is before purchasing. Good luck.
Some aftermarket electronic ignition systems are designed for the specific vehicle. They are designed so that the unit can be directly installed without any rewiring or changing of the stock vehicle's electrical system.
Others are designed to have a 12 vdc input...period. If you get the latter type, you will have to run 12 vdc to it from another hot wire, as the resistance wire source will not provide adequate voltage/current.
It's really very simple. Read the installation instructions and follow them.
Some aftermarket electronic ignition systems are designed for the specific vehicle. They are designed so that the unit can be directly installed without any rewiring or changing of the stock vehicle's electrical system.
Others are designed to have a 12 vdc input...period. If you get the latter type, you will have to run 12 vdc to it from another hot wire, as the resistance wire source will not provide adequate voltage/current.
It's really very simple. Read the installation instructions and follow them.
Don't forget to mention that the 12 volts has to be in the start position, not just key on. I've made that mistake many many years ago.
Thanks for the encouragement. im looking at the Pertronix module. For those who have installed this unit - did you have to modify from the stock wiring (eg run a new 12 v circuit) or did the stock wires work for you?
[QUOTE=USAFVeteran;1592973539]Don't forget to mention that the 12 volts has to be in the start position, not just key on. I've made that mistake many many years ago.[/QUOTE
I have a Pertronix in my 65 Ford pickup with a 390 it has been going strong for almost 20 years and I have NEVER touched it after I installed it. Fires right up hot or cold wet or dry. That's why I put one in my 73 Corvette and I will be installing one in my 66 283 El Camino just as soon as it is finished. I will never go back to points again.
Again, just follow the instructions with the Pertronix you buy. It will tell you what is needed for proper installation.
If you have a specific Pertronix model number you are considering, maybe someone on the Forum has installed that exact unit and can speak to the specifics. But, that won't change the validity of the above statement.
Thanks 71 and i agree that following directions is paramount. The thing i love about this forum is that there arent many things that i wiuld want to do that havent been done a thousand times previously before by other forum members. Learning from others prior experiences builds confidence. To that end - if anyone has installed a Pertronix module on a 74 (or similar era) and was able to do so without rewiring - please post the part/model number of the Pertronix unit you used. THanks in advance !
Originally Posted by 7T1vette
Again, just follow the instructions with the Pertronix you buy. It will tell you what is needed for proper installation.
If you have a specific Pertronix model number you are considering, maybe someone on the Forum has installed that exact unit and can speak to the specifics. But, that won't change the validity of the above statement.
I just checked and here is my inventory. I have Pertronix ignitors in my 65 Ford Pickup, my 59 Austin Healey 3000, my 73 Corvette my 72 Corvette, my International Cub Tractor and my John Deere tractor. All you do is follow the instructions and run the black wire to one side of the coil and the red wire to the other. Don`t overthink it just follow the instructions and enjoy.
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Originally Posted by gungatim
no offense to anyone, but why hasn't it been brought up that the condenser could be bad? they do go bad. they can be tested. sometimes the wire is incorrectly hooked up or damaged. sometimes the wrong one is installed. the condenser acts as sort of a cushion to keep the points from burning. that is the first thing I would check. Then the grounds. bad grounds can kill the condenser.
then the point cam/point gap. worn cams can cause issues as well. finally, what brand points? cheap Chinese junk or good quality stuff? we see this all the time with older vehicles and bikes, a lot of the replacement ignition stuff is extremely poor quality these days...
BTW, Wilcox is spot on.
I asked if he had a functioning condenser in post #11. "Functioning" was probably a poor word choice on my part, but I don't recall getting an answer from the OP.
Assuming the ignition was working correctly in the past I agree with 69427. A quick check of the condenser would be to pull the dist cap, check to make sure the points are closed, if not rotate engine until they are. Spring the points open with the key on using a screwdriver but make sure you don't earth anything if you can see a big spark the condenser is likely defective. You can also disconnect the condenser and see if there is any change in the spark.
I have been having a problem with points burning after only a few hundred miles on my 1970 350, 350. I would like to convert my original to pointless. Does anyone have a suggestion as to brand and model that they are happy with? Thanks, Rob
Nelson Specialties 800 494 7532
Has a unit by Crane cams. Simple 2 wire hookup replaces the points. uses stock points cam lobe
