stumpers for the gurus, 4 questions I cannot find answers to.

lendaddy · 11:38 AM

Well, here they are the four remaining questions on my install. I beg of you all to please help me as my baby has sat dormant for too long (4 days now). Thank you in advance.

All of these questions refer to a '77 930 which I am installing an MSD 6AL unit in..

1. Now that I have run the appropriate wires to the coil from the MSD box what do I do with the original wires (one red, one white) that went to the two poles on the original coil? Are they now unused and can be tucked back into the loom? Or should one or both also be attached to the coil?

2. Regarding the thicker red wire from the MSD box which is to be connected to constant power(even with the key off) Wayne reccomends connecting this to the starter hot post. I understand the reasoning there entirely, however I (and I assume every other 911 owner) have a constant power lead into the rear fuse box and I am wondering why I cannot tap into power there. The wire is the same gauge as the msd lead but I am unaware as too posssible current draw limitations. Just wondering as it would make for a cleaner install.

3. Regarding the green coaxial wire that exits the distributor. The connector on the end of the distributor pigtail crumbled in my hands when I disconnected it. Now I am left with the two mini male spade connectors at the end of the pigtail. In Wayne's book he says to connect the tach output from the MSD box to the green wire from said connector. Well as I no longer have the distributor pigtail connector and both of the male spades which remain are now interchangable(I don't have the one way only aid that the original connectors gave me) I am a bit lost. The question is which wire from the coaxial wire is considered the "green wire", the shield or the core of the coax? And once I know if it is one or the other do I need to attach the remaining wire to its origianal mate or is it now obsolete and can be tucked into the loom?

4. Also here is a very general question regarding spark plug gapping. When measuring gap should you measure the closest point between the two electrodes or should it be tip to tip measurments? To explain this what I am saying is when I open the gap the outer electrode actually tilts back creating an obtuse angle above the tip rather than a perfectly perpendicular angle, This results in the tip of the outer elecrode being farther away from the center electrode than say .040" back from the tip of the outer electrode by about .012" I would say. I hope that makes sense.

Planter91C2 · 04-25-2002, 06:18 AM

4) when gapping the plugs you can get a right angle on the electrode. on the opposite side of my gapping tool there is a wrench which is like a small notch cutout. you use this to bend the shaft coming from the plug as well as the part going over the electrode. you can get a 90 degree angle easily.

lendaddy · 04-25-2002, 09:59 AM

Sorry guys but I had to bump this. It's killing me!

lendaddy · 04-25-2002, 11:37 AM

Ok, I just found an old thread where John Walker's Workshop stated that The outer wire on the coax is ground, and the centeris the trigger. Now this gets even more interesting because the coax wire goes to the connector that use to attach to the original CD box right. Waynes instructions only show three wires being attached to said connector from the MSD box and the rest of those in the connector go unused. Well I traced the outer shield (ground) from the coax to the connector and it is one that is unused. Does this mean that the magnetic pick up thingy in the distributor goes without ground or does it pick up its ground with a splice somewhere in the loom? This seems odd.

lendaddy · 04-28-2002, 07:44 AM

No one can help me here?

zuffenhausen · 04-28-2002, 09:09 AM

lendaddy,

I hate seeing your thread lying around untouched, and imagining your car doing the same. I know it's a bummer. I've avoided chiming in thusfar because I figured plenty of people have done exactly what you're trying to do and would help you, but that hasn't happened. I wish I had all the answers for you but I'm not familiar with the instructions from Wayne that you're using, and it's been a long time since I did an MSD install. I am more familiar with the Crane boxes, but they both hook up the same way, so maybe I can help a little:

The MSD box should have a pair of wires in a sheath that are for the trigger. This pair of wires should connect to the mag pickup on the distributor. While it's possible it would work by attaching one conductor of the mag pickup to chassis ground and attching one conductor of the MSD trigger pair to chassis ground, the mag pickup signal is very small and sensitive to noise, so it's best to isolate this pair. I know on the Crane boxes the pair is twisted for noise supression, as it probably is with the MSD box too. While the outer conductor on your coax is typically considered ground, I don't think it matters because it's an AC waveform generated through the mag pickup.

As for waiting for all these answers before trying it out, you really don't need to. If you've got the pickup wired like I described above, and you have the MSD box connected to the coil, and you have power to the MSD box, the engine should run. You may not have the tach signal hooked up right, but you'll know that right away when your tach stays silent. Not really mission critical, as it were.

Speaking of power, these boxes can draw a significant amount of current so that's why we always wire them to the starter hot lead. They are internally switched so that when the ignition is turned on, the large power lead and thus the high current supply to the MSD box is enabled. I would avoid connecting the power lead to your engine fuse panel. It would probably be okay, but the consequences if it's not are bad: a fried wiring harness! Unless you know what Porsche's current rating for the engine bay fuse box is, along with the current draw of everything else running off that lead, there's no way to know for sure that you have ample margin for the MSD box.

Good luck!

-zuff

TurboRuf · 04-28-2002, 09:50 AM

Lendaddy,

I installed dual 6AL's in my 930 last summer, so if you have any additional questions let me know.

Zuf took care of your major concerns.

Now if MSD could just shink the size of the 6AL's.

TurboRuf · 04-28-2002, 09:50 AM

Lendaddy,

I installed dual 6AL's in my 930 last summer, so if you have any additional questions let me know.

Zuf took care of your major concerns.

Now if MSD could just shrink the size of the 6AL's.