does it matter if I run an internal or external resistor type coil? I have seen coils with the resistor mounted on the side of the coil, who caries these? for a sbc. Thanks Toqwik
My 55 Pontiac has an externally resisted coil.The only real advantage I can see to it is that it also supplies a spot to run an electric wiper motor(if you can find one).
depends on what the vehicle and wiring are....some cars have a firewall mounted resistor so that would dictate the external resistor type - some cars have a section of resistor wire in the ignition to coil circuit so that would need tyhe same as the first. its for the application where plain wire is used in the ign to coil circuit that the internal resistor would be used.........correct me if any of this is bullshit.....I believe thats how it goes.
Are you sure you weren't seeing a resistor mounted on the coil BRACKET? That was a common practice on domestic vehicles in the mid fifties when the switch-over to 12 volt electrical systems dictated the need for a step-down resistor (ballast resistor) in the coil power circuit. Thecoil bracket had a little tab sticking out of the side that you mount the resistor onto.
I've used a Borg-Warner coil #E40 on everything I've converted to 12 volt. It's an internal resistor coil. Just run 12 volts to it and go!!
I know in a post a while back, I was talking about wiring my car, and a few folks told me to be sure NOT to use an internal resistor coil, to use the external (firewall) mount. Its a sbc with original type points. Any other opinions???
If I am not mistaken, the internal/external resistor type coils are used in conjuction with the type of alternator being used. In other words if the alternator has an internal resistor then you would use an external resistor coil. All that internal/external coils refers to is that there needs to be resistance somewhere in that part of the circuit and it will be located either at the coil or at the alternator. The resistor that some have mentioned earlier, the ones you see mounted on firewalls and coil brackets, are actually used to drop the voltage from the ignition circuit to the distributor. This is a ballast resistor and it works much like a heat sink; it traps and dissipates the excess voltage that is not needed by the points. This is typical application on a vehicle that was a 6volt system and has been switched to 12volts, say for example a flathead. 12volts through a 6volt dizzy will fry points alot quicker than normal.
Dos'nt the resistor need to be matched to the coil,as there are different value resistors,just as there are different voltage output coils? Of course I'm running a flathead,but I don't think that makes a difference. Chuck Fish
The only application that I can think off that it would matter would be in a 60's GM car with an original harness. They used a special resistor wire taped into the harness. It doesn't look like it has a resistor but it does. If you use a resistor coil in this system you will have 2 resistors inline. I personally like to see the ballast resistor. Just one of the old timey trinkets you don't see on the billetmobiles. If you hide it under the dash, be careful they get HOT.
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