MSD Coil wiring to CDI assistance needed (no MSD box)

[David Borden]

Ive spent some time searching and have not found the answer to a couple questions.

Im trying to wire a blaster 2 coil in with the stock points and CDI (no MSD 6 box) in a stock 1974 911S with its 2.7.(I understand it needs to mount pointing up)

The stock coil terminals are labeled A and B. The MSD is labeled + and - like most all other coils. I found lots of threads on wiring a MSD box and the coil but nothing definative on wiring just the coil on 911 my year 911.

The B terminal on the stock coil is connected direct to ground on my car(coil mount bolt). Does - go to ground? I know it sounds like an obvious question but remember something weird about wire coils to points from years ago so just wanted to be sure.

Also, do I use the ballast that came with the coil? Again, CDI Ignition on a 74 911S. Ive seen differing opinions on this from searches. Anyone know for sure?

Any help would be greatly appreciated. Trying to get it done early tomorrow morning so I can give my folks a ride when they come to visit.

David

[James Brown]

you don't need the ballast on a CDI car. try one way and if it doesn't work, switch the wires.

[Walter_Middie]

There are only 3 wires going to the original CDI unit, 2 white wires and 1 red one.

1. One white wire (CDI “A”) goes to the + coil (or transformer) terminal
2. The other white wire (CDI “C”) goes to the distributor points and the tach
3. The red wire (CDI “B” center pin) is +12 volts switched through the ignition switch on the dashboard.

Each of the white wires are wrapped with a grounded shield that is connected to the CDI unit case at one end, and the + coil white wire ground shield runs to the – coil terminal and is grounded on one of the posts that the coil mounts on, the other white wire ground shield is grounded on the engine near the distributor.

A way to remember the CDI wiring is "B" for Battery, "C" for contact (the points) and "A" for achtung, don't electrocute yourself!

The other coil primary terminal goes to ground of course (must be the coil wire labeled "B" on your car).

As James said, no ballast resistor needed.

[David Borden]

Thank you, thank you!! Really appreciate it guys...

David

[304065]

Originally Posted by Walter_Middie

There are only 3 wires going to the original CDI unit, 2 white wires and 1 red one.

1. One white wire (CDI “A”) goes to the + coil (or transformer) terminal
2. The other white wire (CDI “C”) goes to the distributor points and the tach
3. The red wire (CDI “B” center pin) is +12 volts switched through the ignition switch on the dashboard.

Each of the white wires are wrapped with a grounded shield that is connected to the CDI unit case at one end, and the + coil white wire ground shield runs to the – coil terminal and is grounded on one of the posts that the coil mounts on, the other white wire ground shield is grounded on the engine near the distributor.

A way to remember the CDI wiring is "B" for Battery, "C" for contact (the points) and "A" for achtung, don't electrocute yourself!

The other coil primary terminal goes to ground of course (must be the coil wire labeled "B" on your car).

As James said, no ballast resistor needed.

Four wires. . . ground strap to the tab on the case. . .