I have a 911 SC engine harness that I want to modify to install its engine in my GT project.
The car has complete working 914 6 engine and chassis harnesses.
I have already eliminated all the SC fuel injection circuits and want to create a simple
plug-in engine harness for the 6 pin CD ignition and internal regulated alternator.
There are two wires on the CD unit I need advice on.
The 12v power is best sourced at what pin out of the relay board ?
The black/purple (tach pulse) goes to what pin into the relay board ?
The blue wire out of the alternator (charge light) goes to what connection on the relay
board ?
I'd rather keep the 6 relay board.
The coil, starter and oil press/temp are pretty well settled.
TIA
Anyone ?

I can't help you, I deleted my relay board.

D+ will be the wire/connector for your idiot/dash light.

We can build you a custom harness in shop.

Give me a shout if you're interested

Pete

There's all kinds of threads here on wiring. I know one is specifically for an SC engine. Some diagrams came from Auto Atlanta. I have hard copies in the shop. 1st question is your alternator internally or externally regulated?

Just re-read the post, you may need two harnesses if using the factory CDI location. One to run to the relay board and the other from the dizzy (and possibly the coil) to the front of the battery tray.
My set up with weber carbs and MSD is done this way and it's very quick disconnect.

It's internally regulated.
I'm pretty certain I have the alternator wiring covered.
The big red(charging) wire goes to one end of the battery cable or the other.
The fat ground goes to the engine case.
The small blue wire for the charge lamp does not go through the 14 pin
connector.
I will extend a lead from the engine harness to the D+ female (no voltage regulator)
in the relay board.
The circuit then exits the relay board forward through pin 2 (blue wire) to the dashboard lamp.
With that connection I believe the alternator wiring issue is solved.
Input is appreciated

This looks good to me.

You probably know about the extra green wire in the chassis harness, which you can use for oil pressure gauge. If you have the oil pressure sender on the front of the engine, you can pair the oil temp and press wires separately to the engine shelf and across to the front of the engine and it makes a little cleaner install. I just did a 6 conversion and made the harness more modular.

I'll try and confirm tomorrow but pretty sure power for CDI box is term#1, tach signal is term#2

Are you using a factory CDI box?

I use an injector style plug to connect to the distributor green wire, which is a coax cable. One side is the signal and the other the shield; both terminals connect to the CDI box.

The sucky part is the 6 pin CDI box boot is NLA and to my knowledge not yet reproduced

You mean this boot Perry? @IronHillRestorations

Click to view attachment

Yes! Who makes it?? I've got one NOS that I've been holding on to

@IronHillRestorations

One of our suppliers in Europe. I can't give all my secrets away.

Pete

Next up is the tach wiring.
The 911 SC 6 pin CD plug has a black /purple wire that drives the tach.
The tach in our 914s is driven by a black/purple wire.
A 914 6 has a transducer on the relay board for the tach.
I don't know if a '77-'83 SC has a transducer ....anyone here know ?
Anyone with experience who can comment ?
Is an SC tach different ?

http://forums.pelicanparts.com/porsche-911...lity-chart.html

Excellent !
Exactly what I needed. Thank you !
Luckily I have a SC tach on hand to test and run temporarrily