ignition problems?
 

I am running a MSD al6 box with a ready to run MSD dist. #8528 and a blaster 2 coil. The problem is that when the ignition switch is in the run position with engine running it runs very choppy when I turn the key to the off position it runs on and the motor runs like a top with no choppiness. I know how to fix the run on with a diode but what is causing it to run rough. My acc. are dual fans and exhaust cut outs. I have new harnesses from MH all around and have changed to internally reg alt. with harness to match. I have tried to bypass 6 al box and go dist only with no difference. I am lost.
Anyone have any suggestions for me?
Brian

Has this always been the case or are all of these items new?
What timing are you running?
What cam?
What carb?

not always just since reinstall after restoration
32 deg advanced
QFT 830 carb
not sure of cam but not radical

Try unplugging the fans? They use a lot of power. How many amps are they, and what's the alternator rated at?

Any chance the distributor was put in a bit off?
My engine builder said 12 degrees initial and 34 -35 total with mechanical, 32 seems low, but not enough to cause these issues. Hopefully someone else who knows more can help.

I'd say the distributor isn't getting all the voltage it should.

When it's 'OFF' the alternator is just supplying voltage to the MSD.

Re-check your wiring per the MSD schematic.

Also check for good grounds.

:)

The engine should not run with the key off ever. The small red wire on the MSD should be wired to the igntion switch or anything that has power in run or start. The big red wire should go to the battery +. Large black to ground, small black to neg. coil, orange to + coil. Mag pickup (green and purple) should be to distributor or crank trigger.