MSD Ignition box

[PozQB14]

Hey Mike, what kind of shifter do you have? A few years ago, I had a similiar problem and it was my turbo action line lock button that wasn't fully disengaging. I had to push on the wires to ensure the little red button was fully out.

[M120]

I replaced a 7AL2 with a 6AL between rounds after having the car shutdown on return road. Before it shut off the tach was jumping all over the place and would barely run.
I was racing an index class using weight to run the index. I didn't change weight after replacing with 6AL and ran exactly the same ET.
This was with a ZZ4 engine making around 380 hp . 11 second Chevelle

[Adger Smith]

Make sure your coil matches the box you are using.
Chart:
https://www.holley.com/brands/msd/pr...gnition_coils/
There is also a difference in some of the distributor pick ups and boxes.
I think it is analog vs digital. ran into a couple of customers with match up issues a few years ago.
Make sure they are compatible.

[mike britt]

Adger, that is an interesting chart. I have run the Pro Power coil on every car I have had for 40 years but they all had a 7 AL2 Ignition. I wonder why that coil won't work with a 6 A ignition.

[Adger Smith]

Mike,
I wish I had an answer for you. I've had customers that ran into the same issue. Started quite a while ago with a Circle track customer Up grading and I another recently that had a distributor that wasn't compatible with his box.
If I got this right his box was a digital 6 and the distributor pickup was for an analog box. I have 3 coils that I kept with our dyno and a couple boxes. I always liked to dyno with as much of the customer set up as possible.
I've run 7 boxes in all my own cars, never any issues. I have noticed that the 6 boxes have a rev limiter that isn't as harsh as the 7's.