Twin Plug + MSD / Green Wire hook-up

[andrew15]

I've done the searches and still have a couple questions -

Background:
I'm getting ready to put 2 MSD 6AL units into my car and will be using a distributor with the magnetic pickup / green wire from the SC

Issue # 1
MSD says the following connections are correct:
Violet wire - Magnetic pickup signal
Green wire - Ground wire from mag pickup

Many people on this board have said that the MSD wiring is in fact reversed and SHOULD be:
Violet wire - ground wire wrapped around green coax cable
Green wire - Green coax wire

They add that hooking it up as per MSD instructions will in fact lead to timing being off and a high rpm miss around 5k rpm.

Any other opinions out there?


Issue # 2
On the green wire connector, which tab is the green coax and which is the ground cable that wraps it? I've included a picture below with numbers is #1 the ground or green coax?

Issue #3 - more reference than anything
In connecting the MSD green / violet wires to the green wire, it's been suggested you can hack into the loom, or use a Bosch fuel injection connector. The new connector route seems the cleanest way and apparently MSD has a pack of 8 connectors for ~ $13. It's PN- 2400 for reference - I'm going out today to see if I can find a pack and see if they fit.

Thanks,
Andrew M

[Steve@Rennsport]

Andrew:

Issue # 1: Distributor triggering for MSD's; The green wire goes to the center conductor, the violet wire to the shield.

Issue # 2: You can determine which pin is which by using a DVOM and checking continuity to ground on the distributor body.

Issue # 3: Everyone has their favorites, but I use either Weatherpack or Deutsch connectors when adapting the green Bosch 2-pin cable to trigger 2 MSDs'.

[andrew15]

Thanks Steve!
I can't believe I didn't think of continuity of ground!!!!

Do you shield the MSD cables back to the box or just keep the wires twisted?

Thanks,
Andrew M

[Steve@Rennsport]

Originally posted by andrew15
Thanks Steve!
I can't believe I didn't think of continuity of ground!!!!

Do you shield the MSD cables back to the box or just keep the wires twisted?

Thanks,
Andrew M

Hi Andrew:

LOL,....Thats why I get the "big bucks",.......

Indeed, I simply twist them for EFI protection and that works very well. I think its important to mention that its good practice to keep all the wiring as short as humanly possible. Further, MSD units MUST be grounded exceptionally well due to the amount of current they draw above 6K RPM.

IMHO,....I've found that most MSD troubles are directly related to installation errors.

[Eagledriver]

I went through alot of effort to hook up the green and purple wire correctly and still got them backward. You'll be able to tell right away though because you'll have the timing 30 degrees too advanced! Just stick a timing light on the engine when you first start it up. I was fooled for a few minuits because I thought it was hooked up correctly and I mistook the 30-35 degree marks on my crank pulley for the Z1-5ATDC marks! After I reversed the wires the timing was perfect.

Double check the ground for the MSD unit. I grounded it to the metal frame that the old unit was on but the ground wire was loose where it attaches to the frame of the car. Symptoms were intermittant tach signal and car died.

-Andy

[BReyes]

You can rely on this forum to get you through. BTW how far from Calgary to Portland?

Regards,

[afterburn 549]

side pt- Msd makes something that allows you to fire twin plugs ??? I want it ! what is it ? whats it called ??

[andrew15]

They don't make anything per se, they just make it easier to fit and wire IMO.

I'm using:
Supertec twin-plug distributor with a magnetic pickup, but fitting an early case
2x MSD 6AL boxes
2x MSD High vibration coils
MFI Connector to spilt the green signal wire into the 2 MSD harnesses (Green / Violet wires)
Magnecor plug wires

Going a bit further, it's being used on a 2.6 with:
Early aluminum case
92mm P&C - NOS Mahle
S Cams
66mm Counter-weighted crank
40mm Webers

The twin-plugging wasn't a cheap option, but when compared to the cost of some of the other stuff, it wasn't too bad!

Regards,
Andrew M

[afterburn 549]

Got the same dilemma here, think I will have to bite it and go SDS

[Henry Schmidt]

I have been doing these distributors in different forms for close to 20 years so I have seen most problems associated with twin plug and MSD.
First, MSD instructions are correct.
Second, neither wire from the green contact is a ground. There is an A & B wire are two ends of a coiled wire. Testing continuity to the distributor body will produce no result other than open circuit. If you have continuity the coil in the distributor is bad.
Last, best connector is the stock Bosch connector. Use an injector connector.
We also use just one 6AL box to trigger both coils. If you have two CD boxes (the part most likely to fail) and one fails the engine will continue to function on one set of plugs. This has been known to damage the engine. Case in point , when the belt in a twin rotor(3.6) distributor fails an engine failure is close behind. Use one 6AL if it fails the engine stops without damage.
Here is the illustration you should have gotten with your distributor.

[andrew15]

Thanks Henry -
-I did in fact check for continuity and found no result against the distributor body - thanks for the attached diagram, in all my searches I forgot about the different rotation for the early distributors.

- I am using the stock Bosch connector for the Green wire - I've used a FI connector to connect the MSD harness.

- One 1 vs 2 MSD boxes, I've heard some reasoning that one box doesn't allow for full power from the MSD unit - I'll have to look through some threads I've got bookmarked. One box would certainly make my life easier.

Thanks,
Andrew M

[rsscotty]

Henry,

I understand that when a belt goes bad on a 3.6 twin cap distributor the rotor is going to fire for every cylinder at the set position that the rotor stopped on the lower half of the dist. With this being the case, it would be possible for 6 firing events at that plug for every 720 degree engine cycle. Thus the ignition system is still working for both caps. I can see engine damage resulting from this.

I don't see where any engine damage would result if you had two MSD boxes and one box failed, whether you had a 3.6 distr. with the belt intact or an earlier RSR factory type distr. with twin plug , single cap. You would end up running on one set up plugs with corresponing power loss.

[BURN-BROS]

rsscotty, Failure to fire both plugs with the higher compression/fuel yields a recipe for an engine rebuild.