Coils

[YENKO DEUCE REGISTRY]

How many volts is a stock 293 coil? Is there a performance advantage to step up to blaster coil? Does a blaster coil require a ballast resistor - and if so, what exactly is a ballast resistor?

[Verne_Frantz]

Marlin, I don' tknow the specs on the 293 coil, but the "blaster" coils are internally designed to not use a ballast. IF there is a ballast in the original wiring,it needs to be jumped.
Most hi-perf factory coils came with a ballast resistor in the circuit from the switch to the Pos. terminal of the coil. When the switch is in the Start position, the ballast is by-passed by the wiring in the harness so the coil gets a full 12V on the primary. When the switch is in the Run position (or ON pos.), the feed is through the ballast and lowers the voltage across the points to about 3-4 volts which saves point life. That's the purpose of it. IF you use a coil that was designed to use a ballast and it shorts or is by-passed, it will cook the coil. I hope that explanation made sense.
http://www.yenko.net/ubbthreads/images/graemlins/biggthumpup.gifVerne

Also, a lot of cars use a resistance wire rather than an external ballast resistor. In that case, there are 2 wires going to the Pos side of the coil. One is the white braided resistance wire and the colored wire supplies the full 12V for Start. In the On position, a lowered voltage is supplied to the coil through a resistance wire.

[YENKO DEUCE REGISTRY]

I see... interesting. I believe my car has the braided wire deal. That makes sense about the coil needing the whole 12V on startup.

Anyone know if the stock coils go 'bad' over time, and deliver less voltage?

[Mr70]

I just picked up 3 used ones at SCIndy,and then 2 more at Iola last week.
My experience has been they are pretty bullet proof.
Their achilles heel is if the oil dries up or leaks out after abusive behavior.

[Verne_Frantz]

Marlin, Check your shop manual and there should be a procedure for 2 resistance checks of the primary and secondary side. IF you can't find it, I can look up a procedure for you.

Verne

[Salvatore]

Marlin, Maybe this will help you: 1115293 ignition coil (ohms @ 80 degrees F). Primary resistence= 1.77 to 2.5 ohms. Secondary Resistence is 3000 to 20,000 ohms. Ignition resistor loom is 1.35 ohms. Taken from an original Sun Electric Corp. tune-up chart. http://www.yenko.net/ubbthreads/images/graemlins/3gears.gif

[Chevy454]

Make sure you go with an oil filled unit...don't remember on the Blaster, but Accel offers both the epoxy & oil version for the same application...oil handles the heat better and is supposed to be more durable.

[SmallHurst]

Marlin,

When I replaced my original Pertronix setup with the Ignitor II setup, I went with the corresponding coil (60 KV if I remember correctly). It called for the removal of the resistor wire to the coil. If you have a coil that is designed for 12 full volts, it will not lose as much voltage at the higher RPMs as the coils designed for the ballast wire/resistor. It will lose time for coil saturation as the revs go up, but the higher voltage going in will allow for less of a drop off in working voltage.

One of our friends was at Martin was having trouble with his motor breaking up and not wanting to rev beyond 4500 rpm. Two sage individuals from Canada told him to close the spark gap on the plugs. His old coil was not producing enough voltage at the higher revs + the higher compression of the motor to jump a gap. Close the gap, less voltage to arc the plug= best performance out of the car ever. 13.07 out of a 1964 Merc 427 Maurader!!! http://www.yenko.net/ubbthreads/images/graemlins/grin.gif

[YENKO DEUCE REGISTRY]

Good info Rusty. So, if you have more voltage from the coil, does that mean the spark gap should be opened up a little?

[@wot]

Correct.

[cib12]

most coils for point systems put out 20,000 + KV's (stock) after market was more and also TI was higher-check a sun chart- there great for info- more than most realize

[cib12]

on a camaro with the white wire going to the postive side of the coil(this is resistance wire) check the voltage with the key in run postion or if a ballast res just check the voltage on both sides and compare them-if i remember right it should be around 8 volts. an old retired teck

[John Brown]

[ QUOTE ]
on a camaro with the white wire going to the postive side of the coil(this is resistance wire) check the voltage with the key in run postion or if a ballast res just check the voltage on both sides and compare them-if i remember right it should be around 8 volts. an old retired teck

[/ QUOTE ]

The 8 volt thing only works if the engine is running. If the points are open and the engine isn't running you will have battery voltage (very nearly). If the engine isn't running and the points are closed, voltage will only show about 4-6 volts.

Ask me how much I lost betting an electrical engineer that there should be 8 volts all the time
$10.00 in 1974 dollars .