Voltage to points

[JSeery]

Originally Posted by 40cpe

It seems like any change I make will take a good while to show the results in points life.

Yep, but it doesn't affect much but the rate of wear on the points.

[tubman]

Originally Posted by Jack E/NJ

tubman>>> Plus, there is the added complication of mounting it externally>>>


I've always considered them an extra added attraction. The only complication is they occasionally need a maintenance buff to show off their hidden beauty . 8^) Jack E/NJ

Yeah, it's a good "fake-out". When we were high school kids, we used to buy the originals at "The Big Wheel" speed shop on Lake Street in Minneapolis, mount them on the outside of the stock distributors in our cars, and tell everyone we had a "Mallory Racing Ignition".

I think they were $3.85 back then.

While we were at it, we'd strip the paint off of the top tank of the radiator and hit it with that same "Brasso". That brass sure took a good shine, but became another maintenance item.

[koates]

Originally Posted by 40cpe

I had a Pertronix unit in the distributor at one time using this coil. The name doesn't mean anything, just the ohms. I have a few more coils on the shelf, one being an old Ford yellow top coil, and none have any more resistance. I don't understand why I'm getting such high amps using the often recommended resistance. It seems like any change I make will take a good while to show the results in points life.

Swap the Flamethrower coil for your yellow top Ford coil. Those yellow top coils are excellent coils and long lasting as well. My 1970 Ford Falcon 302 V8 still has its original yellow top fitted and never a problem. The original resistor with these was a special wire built into the wiring loom. Regards, Kevin

[40cpe]

Originally Posted by koates

Swap the Flamethrower coil for your yellow top Ford coil. Those yellow top coils are excellent coils and long lasting as well. My 1970 Ford Falcon 302 V8 still has its original yellow top fitted and never a problem. The original resistor with these was a special wire built into the wiring loom. Regards, Kevin

I don't mind swapping to the Ford coil, but the resistance measures the same. Do you have the resistance value of the wire feeding your Falcon coil?

[koates]

Originally Posted by 40cpe

I don't mind swapping to the Ford coil, but the resistance measures the same. Do you have the resistance value of the wire feeding your Falcon coil?

I knew you would ask me that. I grabbed my 1970 Falcon factory shop manual genuine one and here are some useful specs for you. Coil primary resistance is 1.40 to 1.54 ohms. Secondary resistance is 8000 to 8800 ohms. Current draw engine stopped is 4.5 amps. Engine at idle speed is 2.5 amps. Primary circuit resistance wire resistance is 1.30 to 1.40 ohms. All tests were at 75 deg F. So therefore your total primary circuit resistance should be approx 3 ohms. Condenser is .15 to .20 mfd. All official FORD MOTOR Co Specs. Hope this will help you. Regards, Kevin.

[40cpe]

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Thank you for the very helpful information. We all seem to be on the same page as far as the amount of resistance. I'm going to order a Fluke multimeter that will measure up to 10 amps and try to reconcile ohm's law and the reading I get. Thanks to everyone who has contributed.

[koates]

Most work I do on older cars (pre 1975) I use an old automotive test set which consists of two meters. A voltmeter analog type with 3 scales and a pointer which measures DC volts from 0 to 50 volts. An ammeter analog type which measures 0 to 60 amps. It also measures minus 10 amps. The set also has a variable rheostat which can simulate various battery conditions. It was made for testing and adjusting generators, alternators and voltage regulators. It is more suitable than many digital meters which tend to jump around on their readings because of the radio frequencys that old cars tend to transmit into the atmosphere. El-cheapo digital multimeters are useless on old cars. Regards, Kevin.

[1948F-1Pickup]

An original Ford yellow top coil would be ok. The offshore-manufactured reproduction item is pretty much junk though.....

Ignition Points in 2020 are perplexing to me. Seven vehicles here and nothing has points in it. On the truck, I couldn't even get to that window on the distributor cap anyway. Literally anything inside the distributor is better than points in my opinion.

[Scotty's 52 F3]

I converted a chev Accel dual point to replace my Load o Matic a few years ago. Used a Bosch blue coil as suggested here on the barn, recurved it as suggested and haven't touched it since.

I should probably hit Tubman up for his condenser so I have it when I need it.

[koates]

Originally Posted by 1948F-1Pickup

An original Ford yellow top coil would be ok. The offshore-manufactured reproduction item is pretty much junk though.....

And what brings you to the conclusion that the repop ford yellow top coils are pretty much junk ? Just heresay or actual experience. Not a good idea to spread unconfirmed rumors. I have one of those repop yellow tops on my 66 mustang and it has been fine for eight years and with plenty of driving too. Regards, Kevin.

[Tinker]

makes sense a yellow top would work on a 12volt system with just a ceramic 6v resistor. As they kept the points and dizzies 6v on early yblocks and used a yellowtop coil.

[BUBBAS IGNITION]

Been reading this post and trying to stay away.......

After training techs for over 30 years i have a lot to say :

There are some good comments in the thread
1=ford yellow top is a great coil and very stable with resistance values

2=pertronix coils are off shore and the cheapest coil money can buy , dont maintain resistance very well .......

3= 12 volt current is between 3-4 amps and that will work very well

4= a 1.5 ohm coil and a 1.5 ohm resistor is good , so 3 ohms divided in to 12 volts gives a current flow of 4 amps

5=no one has discussed voltage drop , so lets say battery is exactly (it isnt) 12 volts then the ressitor should drop the voltage 1.5 ohms x 4 amps = voltage drop of 6 volts then the coil is 1.5 x 4 amps = 6 volt drop so i theory the coil and resistor drops the entire 12 volts with very little going across the contacts. (perfect world ) but the battery is more than likely 12.2 volts which would leave .2 at the points .
PERFECT !!!

Now start the car and the battery goes to 13-14 volts , the excess volts or lets say 14 volts then the increase has got to be asorbed by the resistor and the coil .

The most important wire in the system is the calibrated wire going from the coil to the distributor (usually a finely stranded lead wire designed to drop the excess voltage from the coil negative )

[40cpe]

Following up on this thread: I have gotten a good education on ignition resistance theory from all you good folk's comments and facts. In looking for an amp meter I could depend on, on ebay I found a Weston 10 amp meter from what appears to be an industrial panel. I got it for cheap, so I bought it as a special purpose tool. So using a 1.8 ohm ballast resistor and the 1.4 ohm coil on a 12.3V battery, the meter shows ~ 3.6 amps engine stopped and 2.1 amps engine idling. From what you are telling me, it is about perfect. I will now buy a better set of points (I hope) and get on with life. By the way, I found the resistor increases to ~ 3.2 ohms after running a little while. Thank you all for your very helpful information.

[koates]

40cpe, YEP, you seem to have it all correct now. The current draw in the coil primary circuit is most important ,but most guys just overlook doing those tests. When the resistor is cold and its ohms resistance is low that allows for a higher voltage at the coil for cold starting and when the resistor warms up (ohms increases) the voltage is reduced at the coil for hot starting and also allows a longer point life because of reduced current draw. Make sure you align your contacts perfectly parallel to each other so they have a long working life. You are good to go. Regards, Kevin.

[G.M.]

Almost all condensers will read good cold. You need to heat
them to 250 degrees and test them. When Skip rebuilds a
coil he asks the customer to send a few condensers so he
can hot test them. ALL stock new or used old Ford coils get
real weak when they get hot and come back to life when
they cool down. I have mounted small fans blowing cool air
on the coil which helped. Skips rebuilt coils run good when
hot. Skip puts a full 6 volts or higher on a coil to heat them
up until you can't pick them up and after his rebuild still work.
He has been rebuilding coils for well over 20 years and NEVER
charged to repair one that failed, except ones that left the
ignition switch on. If the points are open this is not a problem.
But if the points are closed the windings are like a resister and
get very hot. This melts varnish off the wire in the coil and shorts
the winding you will even have the potting material melt, xpand
and crack the case. Skips coils are insulated with an epoxy on
the wires and can take higher temps. Maybe installing a small
pilot light that is on when the ignition switch is on will save a lot
of coils. A small LED will work. You don't want much over 4.0 volts
to the coil on 6 or 12 volt systems or you will arc the points. G.M.