[Orange911S]

This has been a bit of a saga and I put up a couple of other posts regarding earlier chapters of this story. The replies are very insightful and helpful.

I have been chasing ignition issues since I put in an MSD 6425 and MSD coil to replace the perma-tune CDI that went bad.
I have a '77 911S, stock engine with a little over 34,000 miles. The car came out of retirement last fall and had a good going over and ran well until the no start episode that turned out to be an ignition issue. Here is what I have done to chase the problem:

- Replaced the Perma-Tune and stock coil with MSD. Per the instructions in Wayne's article, I used the three plug connector from the Perma-Tune to attach the switched power and the trigger wire. I used spade connectors and wrapped the connections with electrical tape. I used the ground bolt on the chassis just forward from the electrical for the ground for the 6425. I have rechecked this a few times and it remains tight. The hot power is connected to the starter, I ran the wire between the engine and the firewall and down the hole above the starter near the right rear shock.

- I also replaced the cap and a new non-resistor rotor.

- I had serious backfire (so loud people grabbed their children and ran) and stalling issues a few times and replaced the MSD coil (once in a 7-11 parking lot and once at the gore point of an interstate on-ramp) with the original coil. I also replaced the coil to distributor wire. This "solved" the problem for only a short time. I don't know if I was getting interference from the trigger wire and that caused a failure in the coil, but twice when I put in the old Bosch that got it running.

- I also set the timing and the dwell. The engine was running fine before and the timing was not far off, but the pita that the points were caused me to decide on going the Pertronix route.

- I replaced the plug wires last weekend with Clewetts and regapped the plugs to .045 from the factory settings. The plugs were replaced 2500 miles ago and appeared to be in good shape. After this I was still getting misses at high RPMs so I was babying the car around on surface streets. Not the ideal way to enjoy a 911!

- Yesterday I reread the MSD instructions and figured that I needed to clean up the placement of the trigger wire. I had not shortened the original wire and pushed it to the back of the engine compartment on the left side. Yes, this was not the brightest thing to do, but I thought that I would get to it sooner than I did. The car died twice on the way home yesterday and "rearranging" the white wire each time allowed me to get it started and make it home.

- Last night I shortened the trigger wire and laid it on to the ledge under electrical panel and tucked the three wire plug up there as well.

- I have still not shortened the wire (orange and black) from the MSD to the coil. It is snaking around a bit, but I am trying to do only one thing at a time.

- I have a Pertronix Igniter II and Pertronix coil that I plan to install soon, but would prefer to have some of these other issues worked out.

OK, shortening the wires seemed to help, but I still got a couple of small backfires and it stalled at a light on the 5 mile drive to work today.

So here are my questions:
Does this seem to be an EMI issue, and if so, can I put some sort of shielding on the trigger wire?

Is there a better placement for the trigger wire?

Could the old three plug connector be the issue?

Is the chassis ground connection a potential problem?

Could the coil wire (orange and black from the MSD) be picking up EMI and causing this kind of problem?

Am I missing something that could do with the distributor?

Will switching to the Pertronix solve any of these types of problems?

What questions am I not asking?

Thanks again. This forum has been very helpful.