do you have a video of the misfire?

Yes, the resistor is the weakest point, usually it is very easy to see as the rotor melts a bit or the resistor expands and cracks the plastic.

But sometimes it looks normal even after the resistor burns.

Also if you get the green and purple wires from the MSD mixed up it will run, but run rough, check to make sure the green and purple wires are correct.

Somebody mentioned points above, I don't think you have points do you?

The Green and purple wires run to the distributor pigtail, it's a funky shielded coaxial concoction, but try reversing the green and purple wires and see if it works better?

If you have points or pertronix it is a white wire for point trigger. If you have a magnetic pickup it will be green and purple.

The polarity on the magnetic sensor can be reverse, but I have no personal experience with that.

I would check the signal from the points / magnetic....whatever you have into the MSD. This is best done with a scope although you could use a volt meter.

"Point here is the MSD puts out at least 2X what the bosch did so you need to be sure that the wiring is right."

And that's a real problem! The complete ignition system, i.e. the rotor, cap, ignition
wires, cap wire connectors, and the spark plug connectors all get over-stressed
whether initially or long term. There's really little to no benefit in over-stressing
the ignition system beyond what's necessary in ignition energy and voltage.

Brought on by a no start issue.....

Hmmmm.......

95% dwell or open condenser?

1.) Ran pretty well....2.) slight misses....3.) Backfire.....

Kettering ignition system (coil/points/condenser) w/open condenser or 95% dwell (rubbing block worn down) would result in the low coil primary voltage arcing across points as soon as they open ever so slightly, no coil secondary plug firing = NO START.

CDI w/open condenser .... No point BOUNCE filter....Plugs fire EARLY as points open AND possibly again as they close.

While a properly functioning condenser would have little affect on the plug fire timing with the Kettering ~1-3 ohm system, CDI designers would expect it to substantially delay the plug firing timing and therefore REQUIRE re-timing.

CDI w/95% dwell......LATE plug firing, rotor nearing mid-point between two distributor spark plug "contacts" = Carbon tracking on distributor surface forming over time, miles driven.

CDI w/95% dwell = late plug firing "post" TDC = engine overheats = BACKFIRE!


Or....

Original point dwell was >95% due to rubbing block wear, thereby firing the coil primary, spark jumps across the points = no start.

Initial CDI timing would have been after TDC, but as rubbing block wears more and more CDI begins firing only intermittently.

Someone installed new points but didn't properly lub the rubbing block?

Forget the lub, rubbing block seriously wears down within 800-1000 miless (69 Ford V8, Seattle/Lewistown, MT)

Working from home...
 

OK, the saga continues.
I have been running it and there were a number of trips where it felt "normal"

On Sunday I moved the ground from the MSD to the bolt on the inside fender as was suggested. I took it out for a spin and got up to highway speeds with no issues.

Last night I stopped for fuel, topped off the brake fluid and then ran it home. The temperature gauge went up, just shy of 210, all on a trip less than four miles. There was a lot of heat on the back right fender and heat coming out from behind the tire.

I have seen references to overheat and the backfires so can I assume that these are related?

This morning, it started to miss about 3/4 of a mile from home and then at about the 1 1/2 mile mark I got some serious backfires. I pulled into the left turn lane and it stalled. I did get it started and made it back home. I kept it at high RPMs so it wouldn't stall. I had a few more backfires, but the half mile up my street was smooth and quiet.

From the MSD wiring harness there is a lot of extra white and red wire. I rolled it up and positioned it in the back left of the engine compartment. Is there a chance that I am getting EMI from the wires and this is causing these intermittent issues? What is suggested to do with that wire? Do I need additional shielding?

What seems most logical at this point is to go down the path of John Walker and look into an echlin rotor.

As always, the advice and insights are helpful.

i've had perfectly new distributor caps cause a cross-fire even without MSD. rare though. i'm not a big fan of MSD. sometimes the multiple spark doesn't go to single spark above 3K like it's supposed to, resulting in a lot of backfiring. the bosch system works just fine. ever get a shock from MSD?

I am picking up a new rotor and cap this morning.
No I haven't gotten a shock from an MSD - that sounds, well shocking.

Do you think EMI is an issue with the extra wire? If so, what do you recommend for shielding?

craig had problems with a new set of ignition wires.

i dont think he should be using a condensor.
i never had one on my 2.7.

If the 2.7 used CDI that would be fine, with Kettering a condenser is REQUIRED.

If the 2.7 was shipped with CDI there very likely is a good sized, high capacity, condenser inside the CDI on the incoming point "signal".

If there is no condenser then I would suggest adding one to filter out contact point bounce.

The MSD design may have been expectant of a condenser.

Close together in time multiple sparks are not likely to cause back-firing, but non-filtered contact bounce as the points later close well might.

as the rpms get up there, 3K and above , there's not enough time for multiple sparks.

If the MSD significantly improved spark energy over the older setup you could have something as simple as arcing from one or more spark cables to some ground point.
Did you try looking into the engine bay very late at night in pitch black conditions? Your looking to see if any arcing is visible anywhere along the ignition cables or near the coil it self.

If you go back and read my post #7....this is what I think fixes your problem, based on others with the same issue and getting their feedback.

Start with a resistor plug wire set like Clewett, resistor plugs and a separate harness for the MSD, only as long as needed.....not tied in with the factory harness. If your wire harness is coiled up from being too long, this can induce EMI problems from what I have experienced in the dyno room. If any of the MSD harness crosses ignition wires, try to do it at a 90 degree angle.

1500 RPM for the rotor, 6 firings for each rotor revolution, 6.666 milliseconds between plug fires. There is most certainly enough time electronically, but the real question becomes "where" is the rotor "pointing" when that second firing occurs. As each plug fires, the next cylinder to fire will be at BDC, beginning its compression cycle, intake valve CLOSED, no opportunity for backfiring there.

So, just as long as that "second" firing occurs within 2-3 milliseconds, before the rotor is closer to the "next" plug connection than the plug just previously fired, no harm, no foul...

Plus, even were the second firing later than 3-4 milliseconds there is more chance for pre-ignition, not backfiring

Sure glad we now have COP ignitions....

We'll see
 

OK, here's the rundown from last night. I stopped by the local Napa for the eichlin rotor and a new distributor cap. I thought this would be a pretty easy install and was looking forward to getting out on the road.

The rotor and cap were easy enough. The old rotor had a resistor and from what I read on the forum knew that with the MSD I didn't need that one anymore. The rotor was a little tight getting out, but it worked. I dropped the new one in and replaced all of the wires.

I then went after the wiring that I had coiled up and tucked away from the original MSD install. When I took the plastic cover off of the wiring panel I noticed that one of the MSD rubber mounts had broken. This would cause the MSD box to vibrate while driving. I did not know if this could have caused an issue, but it did require me to pull the aluminum panel and redo the mounting.

That took about an hour, part of the problem is that the nuts that MSD sent with the mounts are a smidge too small and getting those undone while gripping the base of the old rubber mount was a pain. Once done, I uncoiled the wires and laid them out towards the shock mount on the deep part of the engine compartment.

Feeling pretty good about this, I hooked up the battery, wrapped up my tools and went to fire it up. All crank and no fire. Damn!

I went to the back and found staring right back at me was the orange wire from the coil - without its connector on. OK, unhook the battery (can't be too safe) and I redid both the positive and negative connectors with extras from the MSD bag of goodies that came with the CD box.
Hooked up the battery again. Went to turn it over - all crank and no fire.

This time, I had my son turn the key and noticed that the MSD box was lighting up and I felt good about the connections there. I double checked the spark plug cables and the wire from the coil to distributor - Aha, this had to be the one - right?

OK, this time it did fire and it was a nice smooth idle.

It was getting dark and dinner was ready so I needed to clean up and call it a night.

Had their been misses I would have shot video in the dark for any arcing, but that was not the case.

I am headed to work and will add photos and provide an update in a bit.

Got it on the road and pics
 

I fired it up and it idled weakly and died a couple of times. I was able to restart it with no problem. I backed out of the garage and it was still idling - about 600 - and had one small back fire.

I have about a quarter mile down the street before my first stop sign and that was smooth and the idle held at about 900 - 950. The rest of the drive (a couple of miles on city streets and a couple of miles on the freeway) was uneventful. At the onramp and offramp the idle was steady at 950. No misses and no backfires.

I feel pretty good about where this is, but will keep an eye on things over the next few days.

Here is a shot of the new cap and old cap and rotor:
http://forums.pelicanparts.com/uploa...1397061493.jpg

Here is the old rotor. It was a little tough to tug out of there, but ended up coming straight out:
http://forums.pelicanparts.com/uploa...1397061512.jpg

Here is that mess of wires from the MSD intstall before I undid the coils:
http://forums.pelicanparts.com/uploa...1397061530.jpg