Is anyone running an aftermarket ignition?
 

Long story. It's in a stock liter 78 911SC race car. We updated the tach and used a MSD ignition to keep the tach signal happy.

Now the car isn't running right.

Do you need to change cables etc to make this work correctly?

How did you guess?

Even MSD recommends carbon core ignition cables.

Not sure about the carbon core (Electromotive mentioned to use them) but I just order some KV85 from Magnecor.

Enjoy the reading; MAGNECOR Race Wires: WELCOME TO MAGNECOR!

Extract from Electromotive Set-up Instruction:

C.8. Spark Plug Wire Selection

The TECgt outputs an extremely high-energy charge for the ignition coils. Resistor (carbon) core wires work best with this charging method, since they absorb electrical noise generated by the coil firing events. Use 8mm or larger RFI and EMI suppression wire with GM boots. We recommend using a carbon core-style suppression wire with a resistance of 3,000 to 5,000 ohms per foot. SOLID CORE WIRES SHOULD NEVER BE USED. Do not be misled by spark plug wire manufacturers claiming to give you a “power increase” from their wire. The bottom line is that with our charging method, different spark plug wires simply do not make a difference in terms of spark energy. However, there is a huge difference in noise generated by different spark plug wire types (solid core wires generate a very high amount of noise with our system).

Quoted from Magnecor’s Website:

“What is not generally understood (or is ignored) is that the potential 45,000 plus volts (with alternating current characteristics) from the ignition coil does not flow through the entire the length of fine wire used for a spiral conductor like the 1 volt DC voltage from a test ohmmeter, but flows in a magnetic field surrounding the outermost surface of the spiral windings (skin effect). The same skin effect applies equally to the same pulsating flow of current passing through carbon and solid metal conductors. A spiral conductor with a low electrical resistance measured by a 1 volt DC ohmmeter indicates, in reality, nothing other than less of the expensive fine wire is used for the conductor windings!
__________________________________________________ ____________________________________
TECgt Manual Version 2.0 - Page 48 - ©2008 Electromotive, Inc.

Electrical devices, including spark plugs, use only the electrical energy necessary to perform the function for which such devices are designed. Spark plug wires are nothing more than conductors, and whereas a bad ignition wire's inefficient conductor can reduce the flow of electricity to the spark plug, an ignition wire that reportedly generates an "increase" in spark energy will have no effect on the spark jumping across the spark plug gap, since the energy consumed at the spark plug gap won't be any more than what is needed to jump the gap. For a more obvious example of this, a 25watt light bulb won't use any more energy or produce any more light if it's screwed into a socket wired for a 1000watt bulb.”
Due to the extremely high energy in the TECgt coil charging circuit, spark plug wires may wear out faster than with a standard ignition. As such, it is recommended that the wires be checked periodically for carbon tracking caused by a breakdown of the internal conductor element. Looking at the plug wires in a dark area and wetting them with a spray bottle of water will reveal carbon tracking. Pay close attention to the exposed section of the spark plug (where the rubber boot ends) during the test. To maximize spark plug wire life, keep the lengths as short as possible (i.e. mount the DFU as close to the engine as possible). Replacement of the wires on an annual basis is recommended for high-rpm/high-horsepower applications.
For an extremely high-quality wire with excellent noise suppression, we recommend the Magnecor brand. Specifically, their “Electrosports 80” 8mm wire is very good with our system. Custom wire lengths and ends are available from them so you will not need to crimp the wires yourself. They can be reached at (248)669-6688 or on the web at: www.magnecor.com . Taylor Pro-Wire Silicon Resistor wires also work well.

Switch the green and purple dizzy signal wires.
Don't ask why, just try it. Good chance it'll start right up and purr.

Wow, that was quick. Thanks guys! I'll let you know how it turns out.

Bet he changes the green and purple wires first! :D

I hope he does.

Make sure the MSD has a good ground and a good source of 12vdc. they sort of need more amperage to run than the Bosch CDI.

Is this a new MSD install? Make sure you coil is good as well.

A good CDI can make the 911 run great.

I use a Daytona-Sensors CD1 and CD1 coil and it is great.

There are better answers than MSD.......some of them are even plug compatible like the ************ 911 CDI boxes. I hear they are great and they come in 3 pin and 6 pin configurations.

I know the shop changed some wires... Not sure what else they did. All good now. Appreciate the help!

https://lh5.googleusercontent.com/-m...-no/15673.jpeg

Msd
 

If I remember correctly, the MSD requires about 1 amp per 1000 rpms. So the main power lead should have access to at least 8 - 10 amps of power. Before my recent rebuild, I used an MSD 6A w/Magnecor wires which worked quite well. For the rebuild, I switched to an Electromotive XDi twin plug system (which also works quite well!).