I have the pertronics on my 69 350/350, couldn't hardly believe the difference on first start up.

 

Measured the resistance across the coil and had 4.7 ohms.Thanks again for you're help, Rob

 

Man, that seems excessive, even for a "self ballasted" coil. Respectfully, are you confident that measurement is accurate? At worst case high limit alternator voltage (14.4 volts), that means your primary current is only three amps (and certainly less at an alternator voltage of 13.2 volts). Your points shouldn't be overworked at that current level.

You indicated that you have a new condenser hooked up. That's good, assuming it's not faulty. Next question I have to ask. What's your dwell setting? Just trying to see if there's any condition where the current conducting duty cycle is high (ie: long dwell period), and the points barely open before starting to close again, increasing conditions favorable to arcing.

BTW, I'm assuming that the points brand you're using is reasonably well manufactured, and that the two contact pads aren't so misaligned that all the current is flowing through a tiny pinpoint area when the points close. Let me know if that's not the case.

 

I use a Pertronix ignitor 2 and it is great. I can turn the rev limiter down to 3,000 rpm when my brother wants to borrow my car

 

 

12 volts to the coil continuous will burn points faster than you can imagine and will cause a burning problem increasing the failure rate. This has been an issue all the way back to 1963. The resistance of the ballast resistor to lowed the input voltage to the coil as the heat increased in the resistor. The idea is to have a full 12 volts upon start up but have it drop as the resistance wire (or ballast resistor) heats up.

I have the MSD 6AL system in my 72 (which I'd never buy again, to much buck for the bang), I have the pertronix system in my 62 which I love.


Willcox

 

The whole point of the starter solenoid shunt wiring to the coil C+ terminal is to restore the coil primary current to normal levels despite the system (ie: battery) voltage being dragged down due to all the current being sucked out of the battery to feed the slow turning starter motor on cold winter mornings.

The TSB has nothing to do with the OP's problem (if he is accurately describing his problem). The TSB suggests a change to a higher ballast resistance, which will reduce the primary current through the coil windings and points. Assuming a typical coil primary winding of 1.5 ohms, the addition of a 1.8 ohm ballast resistance in series yields 3.3 ohms total primary circuit resistance. (Assuming 13.2 volts from the alternator, that yields 4 amps of peak primary current through the coil and points contacts.) The OP states he has 4.7 ohms in his coil. (13.2/4.7 = 2.81 amps, 30% less than the safe current recommended by Chevrolet.)

There is still some information missing from the OP's issue. I'm still curious about a few things:

What is his dwell setting?
Are the points contact mating surfaces parallel over all the surface?
Is he confident that the condenser is working correctly?
Is there any shorting/arcing happening across the secondary to primary terminals?

 

The dwell setting is 30 degrees at idle down to 28 as rpms are increased. The points look mated. I assume the condenser is working correctly as it was replaced same time as the points.There is no arching across the coil that I can see.I think I will start over by replacing the resistance wire and go from there. Thanks for all the suggestions, Rob

 

I agree that the dwell needs to be correct and the point mating surface needs to be parallel.. But I don't agree with your idea that you can run straight 12 volts to the coil and not cook points. Regardless of what readings you see, you can't run direct 12 volts constantly and not expect to burn points out.

IMHO Willcox

 

Hi Avner,

Where did you connect the hot and ground to on your Petronix?


Thanks,
Rob

 

If you have points ignition, the system components need to be correct...and correct for each other. If you can't figure it out, buy a Pertronix unit.

 

I'm not trying to be difficult here, but no. I've described the physics of what's happening in the primary circuit of a points ignition system, and why every points system GM made since 1955 has 12 volts across the points for 15* every distributor cylinder cycle (points open for 15*, points closed for dwell 30* meaning zero volts across the points), and respectfully, all you do is post back that you disagree. Please show me exactly where you think the OP's current wiring setup is causing issues (and out of curiosity, how does the points have any clue if the '63 wiring and the OP's wiring are different?). I stated what the primary current levels are for the '63 example you posted, and also the primary current levels for the setup in the OP's car. There is significantly less current going through the OP's points than the '63 system of discussion. And calculating the wattage dissipated in the points due to any contact resistance or corrosion, the '63 will have twice the wattage heating compared to the OP's points.
As I said before, I'm not trying to be difficult. We're both trying to help the OP diagnose his points durability issue, but so far I haven't seen any info from the OP that points (no pun intended) to an obvious problem source.
Knowing the coil inductance and the condenser capacitance would be very helpful to calculate if the condenser is capable of sufficiently slowing the primary circuit flyback voltage rise (while the points slowly open far enough) to eliminate the points arcing, but that info is virtually impossible to find for most off the shelf ignition parts.

 

Just curious, where did you find an ignition coil with that high of primary winding resistance? Don't remember if I asked, but are you sure that the measurement is accurate?

Edit: I see I asked this question before, but I don't see an answer.

 

Spoke to my Corvette guy and he is going to work on the car next week. I thank everyone for there time and ideas but this is too confusing to me .always was able to do tune ups and change parts but this is getting to technical for me.Thanks again and I post his findings,Rob

 

All cars with points from 1955-1967 used a ballast resistor and all cars from 1968-1974 used a resistance wire which accomplished the same thing as the ballast resistor. The purpose of this resistor (and wire) was to drop the voltage after the initial start up in an effort to pro-prolong the life of the points.

I have no idea if the OP's car has been modified I'm just speculating! Over the years I've seen many instances where on 1968-1974 cars the customers resistance wire has burned. The customer wasn't aware that the speckled wire running to the coil was indeed a resistance wire and replaced it with regular wire, thus running direct 12 volts to the points at all times and causing premature failure.

When I have a customer that complains about the points burning out all the time this is usually the first place I go.

It's also for this same reason when a customer complains that their MSD or Pertronix kit isn't working properly that you inform them to run straight 12 volts to the system and do not use the existing wire from the ballast resistor or the speckled wire on the 68-74 cars.

Willcox

 

Respectfully, in the bolded part above, you are stuck on this voltage myth. Let me ask you a few simple questions. Assume we're talking about the '63 update you posted about.

1) During the 15* of non-dwell (when the points are open), what is the voltage across the points? ____ volts.

If I short out/bypass the '63 ballast resistance like the OP's vehicle, what is the points voltage? ___ volts

2) During the 30* of dwell (when the points are closed), what is the voltage across the points? ____ volts.

If I short out/bypass the '63 ballast resistance like the OP's vehicle, what is the voltage across the points? ____ volts.

3) Right after the points open at the end of dwell (combustion ignition point), what's the voltage across the '63 points? ____ volts.

If I short out/bypass the '63 ballast resistance at the end of dwell (combustion ignition point), what is the voltage across the points? _____ volts.

4) Is there a pattern in these numbers?

These are not trick questions, nor do they take any math. I am just inviting you to think about what is actually happening in the ignition circuit every time the distributor shaft rotates from one cylinder to the next.

 

I'll make this my last post... The facts are simple and easy to understand.

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 OP never stated they didn't have the resistance wire (it was my speculation).

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..

Right after the points open.. the voltage would be what ever is deemed by the ballast resistor.. (or resistance wire)

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.

The OP's car never had a ballast resistor, it has a resistance wire 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...

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.

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.

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.

Willcox

 

I know how to screw in screws and bolt on bolts, but I couldn't point to a point if my life depended on it.

So the breakerless ignition that works great for some of you - what's it doing and when does it do it?

Reading this thread , and even on the LL website- I have no idea other than your car starts faster, maybe.

Someone says no performance increase, but what's are some possible benefits? Like just running better, smoother? Any benefit at a high rpm?

 

In the days before cost effective electronic ignition, the distributor was equipped with a set of "breaker points" that would open and close with a small cam.




A "breaker-less" ignition removes this mechanical part and replaces it with and electronic part.


Here's a link to a how-to article for the conversion:
http://www.corvettemagazine.com/tech...on-conversion/

 

Breakerless ignition is more efficient and better than the old point system. In hi performance cars it can eliminate what is called point bounce.

Willcox