So your saying that the points dist. doesnt run on reduced voltage?

 

Well???

 

Patience!

 

That should be a simple yes or no !!!Your not going to write an essay are you?

 

Correct. Unless you installed a nine volt alternator alongside your 12 volt alternator then your entire vehicle, including the distributor, is running off of twelve volts.
As I mentioned in an earlier post, which because of your question I assume you didn't read, I stated why all distributors (after 1954 obviously) run a on a vehicle system voltage of 12 volts. The coil doesn't need a reduced voltage (if you put an oscilloscope on the coil you will see it regularly hits two to three hundred volts on the negative side), it only needs a limitation of peak current. Voltage and current are two entirely different creatures. The ballast resistor limits the peak primary current. It does not convert twelve volts to six or nine volts.
As a side note, when I converted my '69 to HEI electronics I retained the stock "points" coil. It is still running perfectly after 37 years, the last twenty connected directly to 12 volts without a ballast resistor. The HEI module not only varies the dwell over RPM (a good thing!), it also limits the peak primary current to protect the coil without the performance reduction caused by a ballast resistor.

 

It's been my experience that a majority of forum members enjoy technical explanations of why or how something works. I misjudged your interest apparently. Let's just settle for a simple "You're wrong", and leave it at that. I've not heard anyone else complain about an indepth technical discussion of this subject.

 

I'm wrong about what?I just ask you a simple question-does a point system run on reduced voltage.If your answer is "no" then why does Chevrolet put a resistor wire in to feed it and a second wire coming from the starter solenoid that feeds full voltage during cranking?

 

got to go with dwncchs on this one. HEI runs on full 12v with current protection provided by ignition module. Points system starts on 12 and runs on 9, the resistor restricts the current by dropping voltage applied to the coil on the + side, - side is the points and condensor.

 

Caution, long explanation ahead.

No, it does not run off a reduced voltage. As I've mentioned several(!) times before, there is only one system voltage on the vehicle (12v). During normal operation the coil primary current (this is the important item here, because it determines coil/spark energy and possible coil burnout if excessive) is determined by the system voltage (12volts) and the system resistance (the sum of the ballast resistor and coil primary winding resistance). As I mentioned earlier, and I'll repeat it again, the system resistance is generally in the range of about three ohms (let's assume the ballast resistor and the coil primary winding are each 1.5 ohms). Twelve volts divided by three ohms is four amps. Four amps with a moderate inductance coil will yield enough spark energy to fire the plugs as you go down the road. Four amps will also not burn out the coil or points if you leave the ignition on with the points closed and the engine not running.
Now let's look at starting mode. Worst case is probably a cold winter day with thick oil. The starter will suck a TON of current out of the battery trying to turn over the engine. This high amperage draw will cause the system voltage to drop to as low as six volts. Six volts divided by three ohms is two amps. You now have one fourth of the normal spark energy (coil energy varies by the square of the coil current. Half the current gives you one fourth the energy. Cranking on a cold day is not a good time to lose 75% of your spark energy.). To correct, or "bandaid" this problem, a method to increase the coil energy is needed. We're stuck with the six volt system voltage at high amperage draw, and we're also stuck with the coil resistance (1.5 ohms). How about if we tap off the starter relay so that we get the six volt system voltage without the ballast resistor being in the picture? Six volts divided by one point five ohms is "TA-DA", FOUR amps. We now have full needed coil energy available to fire fuel soaked plugs. As soon as the starter solenoid swiches out, the high amperage draw disappears and we ramp up to twelve volts again. This would burn out the coil and points if the extra connection from the solenoid did not also open. In both of these conditions the coil current was produced by the full available system voltage.
I'm now off to put some ointment on my typing finger.

 

I'm not trying to hyjack this thread but I've got a couple of questions along these lines and it sounds like you guys have the knowlege to help. I've got a 78 with the stock HEI distributor and coil setup (I think). I just bought a Mallory Comp SS distributor (magnetic breakerless) and a Mallory Promaster Coil (#29625). The instructions say if using "OEM Primary (LOOM) Resistance wire, to connect the +12v ignition/switched wire to the + on the coil, in all other cases an "ignition ballast resistor" is needed between the +12v ignition/switched wire. So do I just connect the big red wire that is connected to the "bat" side of the coil right now to the new coil or do I need to put a ballast resistor in before the coil. Also right now there are two wires comming out of the firewall that go to a thing that looks like a condenser (that used to go in an old points distributor), (the wires are a smaller diameter red wire maybe a #18 or #20 and a small yellow wire the same diameter) These come out of the harness coming out of the firewall and go to this condenser looking thing bolted to the intake manifold, after they go to this condensor looking thing a wire comes out of it and goes to the negative side of the coil. What do I do with these wires and this condensor looking thing when I hook up my new distributor and coil.

 

i'm a little confused with your setup.It sounds as if your coil is seperate from your distributor is that the case?Is the coil in the cap in both the new and the old?

 

From what I gather from your description it appears that the Mallory electronic module is what we call a "dumb switch", no insult intended. It apparently has no current sensing or protection ability so it requires an external series resistance to protect the switching transistor and the coil from excessive current. I would expect that there is minimal resistance in the harness of your '78 due to it originally having an HEI distributor. It looks like you would need to purchase a ballast resistor, but it's a crap shoot what size unless you know what the current capability of the module transistor is and the inductance of the Mallory coil. Too much resistance slows the coil charge rate (undesirable at higher RPMs), while too little could overheat the module transistor. Unless Mallory has some definitive numbers on the range of the ballast resistance you could try measuring the coil primary resistance and then add a ballast resistor that mathematically would keep your peak primary current level under 5-6 amps.
Recognize that you soon will have a system with many performance similarities to a points system. You will have the slow coil charge up due to the ballasting resistance, and degraded performance during low voltage cranking unless you run a shunting wire from the starter solenoid. The upsides (compared to points) are a slightly faster coil shutoff time (faster is better) and no points wear. But you already have all that good stuff and none of the bad with the HEI. I can't tell you specifically what wires originate from where on your wiring harness, so you'll have to debug that locally. If I was to guess, I would most likely guess that the wire with the capacitor (condenser) goes to the coil + side so it filters out noise caused by the module transistor switching the coil primary current. Electronic systems seldom use a condenser on the - terminal (unless there are electromagnetic interference issues) as that defeats the fast switching advantage of a transistor versus points.
Good luck with your conversion, and remember to store the HEI system in your garage in a location where it will be easy to find later.

 

Thanks, I just didn't know if I needed a balast resistor or not, but from what your telling me it does (Mallory makes a ballast resistor for this setup, if needed) I'll just buy that.

Yes on the new distributor the coil is separate from the cap.

 

69427 is correct in his long explaination for a points system. The short form is that the starter solenoid has three terminals. One has a very large cable running to the battery. Another has a wire running from the ignition switch. The third terminal has a wire runnig to the coil so that the coil gets full voltage when cranking.

When the ignition switch is in the ON position the coil gets it's power through a 135 Ohm resistor (Haynes repair manual for a 73 vette) to reduce the wear on the points. The coil can run all day with a 12V source. I've replaced enough points when I was a fleet mechanic to convince me that the points will burn out way before the coil goes bad. The coils would eventually go bad, but not due to the voltage, but due to the heat generated by passing too much power (Volts * Amps) through the coil.

Well...that's my opinion anyway.

 

So then your saying that the engine starts on 12 volts and "runs" on reduced voltage due to the resistor.Just like Chevrolet Motor Division says in their manual #ST-130-68 page 6-10 -- "With voltmeter connected as described for the Cranking Voltage Test,turn ignition switch to ON. Voltage should drop "to" 5 to 7 volts as current is now passing through high resistance wire connected between igniton switch and (+) positive terminal of coil."Thanks Rockn-Roll for agreeing with me that the voltage is reduced for the protection of the points and clearing this up.

 

I have ben away for the last couple of days and unable to respond. I apprciate everyone's feedback.

I called Pertronics yesterday and they said to replace the lead to the coil and dist with a 12v lead verses the factory source with resitance. They also said I needed to upgrade the coil from the original style.

The car is a 69 L46 and the issue started when after a rebuild we did not get the expected performance nor does it seam to match the performance the engine provided on the dyno.

The engine dyno'd at 381 HP / 461 FT LBS with my manifold, distributor and carb. The car is comparitively slow to accelerate but fuel does not seam to be the issue.

My brother thinks the timing chain may have slipped or be fualty / sloppy.

Thanks!

 

Perhaps you need to re-read RocknRoll's first sentence again. Who is it that he said he agrees with?

I've given you engineering descriptions, physics descriptions, vehicle wiring descriptions, and even shade tree mechanic descriptions, all to no apparent avail.
I'm reminded of talking to a child at Christmas time. You can explain how the toys are designed at the factory, the machinery it takes to cast, machine and paint the toys, and the transportation system to bring them to the store for adults to purchase and giftwrap. But they prefer to believe that a fat man in a red suit magically puts them under the tree. The overwhelming majority of forum members who have read my technical description of how the system actually works have not expressed a disagreement with the facts. I'm an engineer. I deal in facts, logic, and physics. Believe what you want, but that doesn't make it correct. This is my last post on this subject.

Merry Christmas.

 

An original points system (used in 74 and earlier) only ran 5-7 volts to the coil. Yes, the car runs on 12v but a resitor wire (used in the late 60's early 70's) or a ballast resistor, used on fords and earlier Chevy's, reduced the car's voltage to the coil,..which kept points from melting from too much voltage/heat.

On cars of this era, a wire (brown wire, about a 14g) was routed from the starter solenoid to the coil to bring 12v to the coil during cranking,..helped with cold starts. Coils of this era were meant to run at the 5-7v range and continuous 12v probably isn't good.

Run a jumper from your fuse box to your coil as I described earlier,..heck, keep your resistor wire connected if you wish (the white wire that has a cotton-like insulation),..won't hurt anything. You'll need the Pertronix coil which is designed for 12v-continuous (the 45,000v coil), and coupled with your Ignitor kit, and good wires, good cap, rotor, plugs, etc, you'll have a high performance ignition that will work up to 7000 RPM and beyond (assuming your distribuor bushings are good), is maintenance free, and looks factory stock. A win-win-win-win-win!

Good luck!

 

Your response is identical to the response Pertronics provided. The voltage from the starter is reduced on run and not a good idea to run the original coil at 12v all the time.

They said for my purposes any good quality after-market coil with an internal resistor (1.5 ohms) will do the trick.

To bad rebuilding the dist., new coil, new wires and new power source did not help much.

My engine seams dead in the mid-range (2500-3500) and less than exciting up to 5500. I am afraid either timing chain slipped or was faulty or I flat out have a bad cam, carb, intake combination.

Appreciate the responses and passion from all and will post the above combination on a seperate post!

 

Thread got pretty heated up. Cars for decades are running on 12volts. Everything in them is designed to work on a 12 volt system. Does that mean that every electronic component needs 12 volts and only 12 volts? No.
A radio is a good example. You apply the 12 volts to the input of this 'system' and it changes the voltages internally to whatever is needed. The same with the older points system with a ballast resistor. That ballast resistor is part of the ingnition system and is designed to drop the voltage. You feed 12 volts into the whole system and it will adjust the voltage lower.

I have a new Mallory HEI distributor. Since it's a replacement for HEI or a points system, there is a litle difference in the installation. For an existing HEI, it's a drop in. For a points system, the ballast resistor must be removed or another source of power will be needed.