Ignition: Ignition Coil & Ballast Resistor Matching

[JoeHall]

Today, I replaced the 56J's ignition coil and ballast resister with new ones from NAPA. I cannot recall when the old coil was installed, but it said, "12 VOLTS, need to be used with external resister". The new coil is NAPA #IC7, and is stamped 6 VOLTS.The old ballast resister came from SI, several years ago. The new resister is Echlin #ICR-23, rated at 1.2 ohms. Neither of the resisters look anything like OEM.

Looking in the Shop Manual, I see the resister is supposed to be rated at .665-.735 ohms. But I cannot find what voltage (12 or 6) the coil is supposed to be. The closest resister I can find to the OEM spec is MSD 8214, which is rated at .8 ohms. But from what I have read else where, the resister is to be matched to the coil. With only modern/aftermarket coils and resisters available, matching them seems a crap shoot (unless they are bought in a set). Guess I will just go with the new NAPA parts from today.

Also, reading a 1956 Packard Service Bulletin, it looks like back then, matching coils and resisters was considered very important. The bulletin cautioned about mixing Delco and Autolite resisters, rated at 1.52 and .665-.735, respectively. Per the Bulletin, the lower the ohm rating produces a hotter spark at the plugs, but if too hot, it can shorten the life of the points, plugs or coil. OTOH, if too low, the spark is too weak, and leads to hard starts, misfires. etc.

Yep. it sure was fun today, climbing a learning curve about coil & resister matching.

[StudeRich]

Looks like you bought the wrong Coil if it is for a 6 Volt System and you have a 12 volt one, according to their OWN marking.

On the other hand, many Coils do not care about the Voltage, like the Flamethrower Coils Pertronix sells, they are for Both 6 & 12, it is the OHM's that matter based on the Number of Cylinders.

[Bud]

If I remember correctly, the correct coil would be a NAPA IC17 which has about a 1.5 ohm primary winding. The IC7 coil has a primary resistance of about 1 ohm which is too low for a 12 volt electrical system with a .7 ohm resistor. I use a ballast resistor with a resistance between 1.2 and 1.5 ohms with an IC17 coil. This combination gives a good spark output with excellent point life. Bud

[Bud]

As an added note, I don't care what Pertronix says about using their Flamethrower coil without a ballast resistor as I've had them get so hot from over voltage that the windings short out causing coil failure. Using a ballast resistor with a Flamethrower coil reduces the output voltage by a couple of kilovolts which in most engines means nothing for performance, but it does keep the coil a bunch cooler. Bud

[gordr]

Why not just get a Bosch Super Blue 12 volt coil, long-beloved by air-cooled VW fans, and dispense with the ballast resistor altogether? Paint it black, and it will look stock, too.

[JoeHall]

Reading several places elsewhere, it seems 6v. or 12v. coil does not matter, as long as the coil is paired with the correct resistor. Looks like Bud has a long time favorite, that I am sure will work well for my 56J, and most other 12v. Studes. However, when I double checked NAPA Online, they sold me the correct coil, per their listing. When I cross referenced Bud's coil (ECH IC17) it comes up as 12v. and NOT for 56J. So NAPA may simply be selling a matching coil & resistor, currently available, but not necessarily, "correct" for 56J.

In 1956, some Packards had Delco coils, paired with a 1.52 ohm resistor, and some (including 56J) had Auto-Lite, paired with a .665-.735 resistor. As mentioned above, Packard cautioned against substituting one resistor for the other. With the 56J's resistor being more akin to (.50-.60 ohm) resisters, used when converting old tractors from 6v. to 12v., I wonder if 56Js did not, in fact, come from the factory with a 6v. coil. Here is one of the tractor resistors, used for converting 6v. to 12v.: https://www.ebay.com/itm/FORD-TRACTO...ss!42701!US!-1

[JoeHall]

As for finding a resistor that LOOKS more like OEM, and closer to factory spec, looks like 1960s to 1980s Mercedes is pretty close: https://www.ebay.com/itm/Mercedes-W1...53.m1438.l2649

[Bud]

Joe, I dug out my old NAPA electrical catalog that was printed in 1996 and it shows the NAPA IC17 coil and an ICR23 resistor for the cars equipped with the Packard engine. I also checked the Packard section and it says the same thing. The ICR23 resistor shows a resistance of 1.2 ohms and is meant for use with the IC17 coil. I'm thinking that the current NAPA catalog has a typo in it if it shows the IC7 coil as being correct for a 12 volt electrical system as the older catalog shows the IC7 being the replacement coil for Packards from 1932 to 1954 and Studebakers from 1941 to 1955. Bud

[Ron Strasser]

I just checked a NOS Avanti ignition resistor P/N 1550556 and it measures 0.6 Ohms measured with a Fluke VOM The listing for the Avanti coil is Prestolite P/N 200607 service coil # P5-13. I don't have the figure for the coil resistance. The listing for a R2 is Prestolite 200714 Service coil P5-57. I measured the resistance of the coil in the Avanti and came up with 1.8 Ohms. It is not the original coil as the original failed and I replaced it with a NOS Studebaker coil but I don't remember its part number
Originally Studebaker had different resistors for the R1 and R2 then changed the listing to the R1 coil for both. It is almost impossible to get a accurate ohm reading as the meters lowest possible reading is 0.1 ohms. Contact resistance has too much of an effect on the reading.
With a 12 volt supply and a 0.6 resistor and a 1.8 ohm coil there would be 9 volts going to the coil and 3 volts dropped by the resistor.
Ron


Ron

[JoeHall]

I just checked a NOS Avanti ignition resistor P/N 1550556 and it measures 0.6 Ohms measured with a Fluke VOM The listing for the Avanti coil is Prestolite P/N 200607 service coil # P5-13. I don't have the figure for the coil resistance. The listing for a R2 is Prestolite 200714 Service coil P5-57. I measured the resistance of the coil in the Avanti and came up with 1.8 Ohms. It is not the original coil as the original failed and I replaced it with a NOS Studebaker coil but I don't remember its part number
Originally Studebaker had different resistors for the R1 and R2 then changed the listing to the R1 coil for both. It is almost impossible to get a accurate ohm reading as the meters lowest possible reading is 0.1 ohms. Contact resistance has too much of an effect on the reading.
With a 12 volt supply and a 0.6 resistor and a 1.8 ohm coil there would be 9 volts going to the coil and 3 volts dropped by the resistor.
Ron


Ron

Hi Ron,
Yes, 9 volts is what the 1956 Packard Service Bulletin said the resistor would drop down to, coming off the resistor and going to the coil. I have read elsewhere, the coil does not matter, 6v. or 12v. What matters is combined resistance, from the coil and resistor. This is probably deeper than most of us ever need to go, but matching the coil and resistor is important, so I understand. I am having fun climbing this learning curve. As for now, the old 56J has never started so quickly, hot or cold. I attribute that primarily to the Demon carb I recently installed. But the ignition is also in a real good state o tune now.

Thanks for your input and wisdom.

Joe H

[JoeHall]

Joe, I dug out my old NAPA electrical catalog that was printed in 1996 and it shows the NAPA IC17 coil and an ICR23 resistor for the cars equipped with the Packard engine. I also checked the Packard section and it says the same thing. The ICR23 resistor shows a resistance of 1.2 ohms and is meant for use with the IC17 coil. I'm thinking that the current NAPA catalog has a typo in it if it shows the IC7 coil as being correct for a 12 volt electrical system as the older catalog shows the IC7 being the replacement coil for Packards from 1932 to 1954 and Studebakers from 1941 to 1955. Bud

Thanks Bud,
Sounds like I need to go back and have a talk with the guy at NAPA. I believe your are right, it almost has to be a misprint. However, from what I understand, the only damage that can occur would be to burn the 6v. coil out. That is, ASSuming the Pertronix ignition module is not the weakest link. Either way, I have spares of both in the trunk.

Thanks Again,
Joe H

[gordr]

When a resistor is identified as a "ballast" resistor, odds are very good that the resistance varies dramatically with temperature, so that it acts more readily to limit current. Measuring its cold resistance with a multimeter may tell you little about its actual operating resistance in use.

[JoeHall]

When a resistor is identified as a "ballast" resistor, odds are very good that the resistance varies dramatically with temperature, so that it acts more readily to limit current. Measuring its cold resistance with a multimeter may tell you little about its actual operating resistance in use.

I had read this elsewhere too. Supposedly, it has more current when cold, when needed most, then reduces a bit as it warms up.

OTOH, your advice on a Bosch Super Blue, 12v. coil, in post #5 above, may be the best idea yet. After reading your post, I read up on them, and they are supposedly superior to most. Supposedly, need to get one made in Brazil, as the ones made in Mexico are reputed to be junk. A lot of deception going on in selling them, i.e. showing a box stamped made in Brazil, then sending one made in Mexico. I am probably going to go ahead and get one of the Brazilian ones.
Thanks Much

[christophe]

For what its worth, I used a red Bosch high performance coil on my 63S (with the pink wire as a resistor) with good results. It was manufactured in Brazil. The # is 0221119030.
They also sell it with the coresponding ballast (1.8 ohm). The # is 0221119031.

[Bud]

At this point in time, I have not had a failure with any of the Pertronix modules I have installed regardless of what ignition coil was used. I have had failures with the Flamethrower coils though. There is nothing wrong about using an original equipment coil orthe correct aftermarket coil with a Pertronix module. I've been using a NAPA IC1700 coil which is the high performance version of the IC17 and an ICR23 resistor on my 63 Avanti since I bought the car in 2005 and have replaced the points once since I bought the car so that must be the correct combination. My 62 Hawk has an IC17 coil connected to the original pink resistor wire and I'm getting the same results. Both ignition systems have plenty of spark output according to my engine scope so I'm happy with the NAPA recommendations. Bud