Distributor Wire Trouble

[Ove]

I'm using the wire loom from my '82 3.0 SC engine on a '75 model 2,7 engine and need some help connecting the distributor.

A green coaxial cable normally plugs into the side of the SC distributor. But on the 2.7 distributor there's a only a single connector, and the green wire connector obviously won't fit.

I haven't cut the green wire yet, but I believe there's an inner signal cable and a braided ground around it (?).

From reading old threads on how to replace the green wire connectors and from looking at wiring diagrams i know that one wire inside the green cable connects to terminal 7 on the CD-unit, the other one goes to terminal 31d. I haven't found more info on this specific problem.

Can i simply run the signal cable from inside the green wire to the connector on the 2.7 distributor or is the problem more complex?

(I couldn't get the picture to upload, will try again later)

[2.7RACER]

Ove,
The shielded wire is grounded at the CD. The inside wire is the signal wire connection from the points to the CD. When the points open and break the ground connection, the CD fires the coil, thus a spark.
A simple wire grounded then ungrounded will cause the CD box to fire the coil. The shield keeps the electrical noise "shielded".

[Ove]

Doug,

Thanks. Should the outer "shield" wire be grouded at the distributor side or can I just connect the inner signal wire to the coil and leave the shield unconnected?
Did the 2.7 engines have another way of reducing electrical noise?

[2.7RACER]

Ove,
I may have led you astray. The 2.7 Distributor uses points and a single wire to control the 3 pin CD box.
The SC CD box is the 6 pin type controlled by a "breakerless" distributor.
I do not know for sure if you can fire the six pin CD box with points.
It may be necessary to convert the 2.7 distributor from points to a "Pertronix" type of solid state unit which uses both wires. Pertronix is the brand of breakerless control used here in the US.
The '82 distributor does not work in a 2.7, as among other things it turns anti-clockwise, where as the 2.7 distributor turns clockwise.
Important to know when you connect the wires from the cap to the plugs.
I'm sorry, I just don't know enough about the six pin CDI unit to be much help.
If you still have the 3 pin CD box the connections are:
CD box A to Coil A. B on the coil goes to ground (earth).
CD box B to 12 volt switched power.
CD box C to the tab on the side of the distributor, the inside wire presently on pin 7 of the 6 pin CD box.
CD box D is ground (earth). The shield connects here.
This part regarding the 3 pin CD box I know and will work.
So, convert your 2.7 distributor to "breakerless" with two wires, or use the 3 pin CD box.
Or wait to hear from someone familiar with the 6 pin box, if it can be controlled with points.
Again, I'm sorry for leading you astray. I was thinking about my car not your SC ignition.

[Ove]

Doug,

Don't worry, I haven't started cutting any wires yet.
I suspected that there could be more to it than just connecting the SC signal wire to the coil.

I do have the wire loom for the 2.7 with the 3 pin CD box connector. However I don't have the 3 pin CD box, and that's why I was hoping I could use the 6 pin SC CD box instead.

Here's a picture:

[Grady Clay]

Ove,

Let me add further confusion to this very important issue.

I understand (rumor of course) that the green coaxial wire
for the SC is backwards from normal. That is the signal
wire is on the outside and the ground is on the
inside. Can someone please confirm or refute this.

Another issue with the SC green wire is it interferes with
the crankcase where it exits the distributor. This occurs
when the distributor is rotated CCW for setting the
timing. You should address this issue while you are
there. No sense in being stranded some day.

Yes, use the 6-pin CD if you want.

Here is the diagram for ’81-> with my color added.

“
"
© Dr. Ing. h,c. F. Porsche A.G.

This too seems to indicate the signal on the outside of the
green coax cable. It is possible the diagram is incorrect.
What is it in real life?

I agree with Doug. The SC distributor turns anti-clockwise
(counter-clockwise, CCW) while the 2.7 turns clockwise
(CW). This necessitates the high voltage ignition wires
to be ordered in reverse. You cannot install an SC
distributor in a 2.7 (and vice versa) without serious effort.
The drive gear on the crankshaft is different!

Best,
Grady

[Ove]

Wouldn't running the signal wire on the outside mean that there is no reduction in electrical noise? The grounding of the inside wire will have no shielding effect on the wire around it, right?
If someone knows which is the signal wire I would like to know.

I found my wire loom with the 3 pin connector today. It must be for a car with carbs, as the blue and green connectors to the CIS are missing.

So what i will do is leave the SC wire loom in place and cut only the 3 pin connector from the other one. I will then connect the wires as Doug describes. A friend gave me his spare 3 pin CD box, so I have everything I need.

Thanks for your help

[2.7RACER]

Grady,
A question remains as to whether you can signal the 6 pin cd box with points. Any ideas?
Thanks once again for jumping in.