View Full Version : How did you setup your aftermarket coil?

Dan Pinder
05-27-2004, 11:34 PM
I am running inta a few problems with my coil setup and I was hoping that someone here may know the correct answer.

I am using a Jacobs Ignition HEI Ultra-Coil, and a Crane-Cams HI-6S CD ignition box.

Okay, so the car runs fine, sort of...

When just the coil is installed:

Car runs. On my SMT6 engine management software I get RPM signal spikes at idle that jump to about 6000rpm, and as such it hits the top of the fuel enrichment map and the extra fuel causes the engine to die. When the SMT6 is disconnected, I still get a bit of a stutter from the engine when it spikes.

When both coil and ignition box are installed:

Car runs and stalls often. Basically the same problem.

Now there are a few possible solutions I am entertaining.

1) Wire up the 4 pin HEI ignition module. So the stock ignition from the ECU goes to the module, and that in turn creates an ignition pulse that goes to the ignition box, which fires the coil.

Would the ECU get the correct readings still with another module in the signal path?

2) Use an MSD or Crane tach adapter, which is supposed to fix the signal on cars that will not run or have problems after installing a CD ignition.

What are your thoughts?

Also, is the positive wire for the factory coil good enough to power my massive coil, or should I run a new wire to the fuse box?

Thank you!

05-27-2004, 11:37 PM
im running a msd blaster2 coil and an msd6a amplifier box. no problems. the plug wire didnt fit in the blaster coil as good as the stock coil so u have to be careful

Dan Pinder
05-27-2004, 11:42 PM
I had a custom wire made. Hmm.. I suppose the tach adapter would do the trick since it creates a new signal. I'm not exactly sure how it does that but.. it apparantly does.

But then.. do I still need the HEI module to get a proper spark from that unit?

I am told I can get a .45 gap at boost with this setup. What gap are you using?

05-28-2004, 12:05 AM
i realy dont know the answer to ur question im sorry

i gapped them to stock i forgot what that is?

Dan Pinder
05-28-2004, 12:16 AM
Stock is .35

With that setup you can open your plugs to .45 for a little more power. If you have any problems bring it down to .40

05-28-2004, 12:24 AM
for turbo dont u want to gap them closer?

Dan Pinder
05-28-2004, 01:03 AM
Normally yes; but with that coil and ignition box you can open the gap up more.

I talked to several sources that recommend .40-.45 with a good aftermarket coil and CD ignition box in a forced induction application.

With a NA motor you can get as high as .55 depending on the coil.

05-28-2004, 09:21 AM
i havent a clue about your setup. the only advice i have is it sounds like the tach siganla wire is picking up interferance from something. it might help to have a sheilded wire as the tach siganl wire to the module. and try to run it seperate from any of the other wires. i had a similar problem with my mega squirt picking up a clean tach signal on my stock ignition.

i actualy had my spark blow out on the dyno with my plugs at there stock gap of .35, i gaped mine down to .28 and its fine now. like you said, if you have a hot spark, you can get away with having a larger gap. but i cant get away with it. :(

05-28-2004, 11:18 AM
are you running stock ignition and coil jim?

05-28-2004, 01:10 PM