I got my engine back together....mounted the radiator, filled it, and tried to start it. No luck. I checked for spark and it was very weak. I went out and bought a new MSD coil. The instructions say that with a stock distributor with points (which is what I have) you must use a ballast resistor inline with the positive wire on the coil. Is this necessary? If so, what is the purpose?
yes i belive you should.. if you were running a MSD dist you wouldn't need it. the ballast is to regualte it so you don't burn the points out. however even older mallory unilights still say you should run a ballast resistor. i'd run it.
The ballast resistor drops the voltage down to the coil. Like Derrick said without it you will burn up the points.
I used the original factory wire to power my Duraspark Coil in my 74 when I switched from points ... is this something I should be concerned with?
I know MSD wants the full 12Volts for maximum output. I would think you would want a full 12volt switched source for the duraspark setup also. If you have a voltmeter check to see what you have. There is a discussion about on this thread http://mmb.maverick.to/showthread.php?t=12178&highlight=duraspark+conversion
NJ, I'm also running the Blaster 2 coil, 6A (not AL) box and the MSD Distributor. I don't use a ballast resistor on my CHP V8 since the MSD distributor handles it. I'd go that route if you could since points are hard to set and very unreliable. My son still gets a kick out of pulling off the coil wire and watching the MSD spark jump from the coil (by the water bottle) clear to the shock tower support! (about 1 foot!). I stuck my finger in the area once and I promise I'll never do it again! Go all MSD, you can't go wrong
The original points setup had a red wire going to the coil from the wiring harness and a black wire going from the coil to the dizzy. The Duraspark setup now has a Green wire going to the coil from the Duraspark box and I reused the original red wire from the factory harness to the coil ... The car runs fine so not sure if this is OK or can I get a hotter spark. Where exactly would the resistor be to remove? I am using the throttle solenoid lead to power the Duraspark box and that is definitetly giving 12V+ when the key is on ...
