to ballast or not to ballast...

[falcon fanatic]

For some strange reason my coil died. So, I just received an MSD blaster 2 coil. It says in the instructions to NOT use a ballast when hooking up to an MSD box, but to YES use a ballast when hooking up to a stock points type ignition. I have neither setup, Instead running a duraspark from a '78 fairmont. What do I do?
My inclination is to not use the ballast, but then my last coil, and Accel hi-po unit, only lasted six months. Maybe there's a connection there?

 

[LaGrasta]

I don't believe you need it, but just check the voltage and see if you're getting 12. That's what you need.

 

[falcon fanatic]

Yeah. Actually, I'm running 12v switched straight from an aftermarket fuse block to the coil. I set up that configuration shortly after realizing that I was only getting 6v to the coil after doing the recommended durspark config. strangely, it didn't seem to make a difference even though I had been running a 12v coil the whole time

 

[LaGrasta]

Sounds like you're good to go just the way you are. I checked my Pertronix set-up last night. I have 12v as well, but I just hooked it up the way the instructions said. I'm tempted to just keep it that way, it's working prefect.
Is there any way you could send a pic of your fuse block setup? Or at least describe it a little. I want to do the same as I am going to be hooking up a few aftermarket items (power windows, solenoid shaved door, a/c, etc.)

 

[falcon fanatic]

LaGrasta,
www.painlessperformance.com
I got it from Summit for $57 plus S&H. It is an isolated fuse block with overload protection and has four switched circuits and three always-on circuits. Took all of about 20 minutes to install. I've used it to give 12v power to my coil and electric fuel pump and to power my radio. I still have four circuits left over. Lots of room for expansion with this puppy, although they make bigger ones, too.
Coupe Boy also posted a picture of a nice one he made himself. My way is easier, though.

 

[Anonymous]

The reasons for adding ballast resistors to coils are: 1.) coil longevity and 2.) radio noise suppression. With a Duraspark, there might be a 3.), which would be: not burning out the Duraspark.

Ballast resistors, when used with high-output coils, often drop the voltage too much, like down to the 6 volts you saw. If that happens, put 2 ballast resistors in parallel to the coil to get it up toward 9 volts while still protecting the Duraspark and the coil.

Most hi-output coils require more current in the primary side to get that extra output. If you draw twice as much current thru that ballast resistor, you'll end up with less than the desired voltage at the ciol, wasted at the resistor.

I wouldn't expect a regular coil to include its own ballast resistor, either. Usually you have to get one somewhere else. 1-2 ohms is about right.

For tough starting problems in cold weather, install a relay (like the Radio Shack 'automotive' relay) across the ballast resistors. Connect the coil of the relay to the starter's terminal so it comes on when you're cranking and drops out when you're running. This will give 12 volts and full spark during starting, which will help if you have lots of advance or cam or CR.