So here is the deal.. Customer car has 4cyl with points and MSD box.
I remove the 4 cyl and put a -6 engine with pertronix in it. I re connect one of the cut wires from the msd box and do a resistance test.. All is good.. Engine runs funky with the MSD connected so I decide to run it with just the pertronix and disconnect the msd.. Engine runs great.. The harness was made by Perry and double checked everything and dont see any issues.. Also note the tach with the msd tach adapt is not accurate so assuming it is running 4cyl signal still?

Any idea's?

Which pertronix is it? (1,2, or 3) Is the MSD box an older one with the solid pigtail on it, or is it the digital with the quick disconnect?

Digital box.. No idea on pertronix as it was already installed.. I looked at it with the cap off and can't tell..

MSD Digital 6A and 6AL Ignition Control
6A - PN 6201, 6AL - PN 6425

@sixnotfour I am with you on this but I resoldered so only 1 loop is cut.. Still runs like crap.. About ready to just use the pertronix and be done with the msd all together if I can figure out the tach.

What tach is being used? Does it read correctly with none of the MSD hooked up and purely off the pertronix? The ignitor module in the dizzy should have a P/N on the side or top of it.

Its. 4cyl tach currently. Could that be the issue?? I looked inside the distributor no part number could be seen. Also note the tach was not hooked up when it ran well..

Oh and no does not read correctly but could not test it when I just ran the pertronix

I took out a Pertronix I recently and the little box is black. Installed a II and the little box is red. Don't know if this pertains to six cylinder or not...

Paul

Well the box is black if that helps?

What plug wires are on the engine? MSD is incompatible with solid core, and they recommend 8.5mm wires. Also, how clean is the cap/rotor?

What coil is it running?

Still run funny with tach disconnected running the MSD?

It has magna core wires. Cap and rotor are new, new msd coil.. Not sure on the tach disconnected. I will try that tomorrow..

How is it all wired up? Should look something like this aside from the tach adapter wiring.

Yup just like that..

It's the little induction box thing that mounts on the plate inside the distributor, just to be clear. The Ignitor I has a black one, the II has a red one. I would assume the black box is a I.

Pertronix wants you to run their coil but I'm running a Bosch Blue Coil. The instructions say that the aluminum plate resistance should be less than 0.2 ohms when grounded to the battery on a multi-meter. And there's a voltage test as well. Instructions are on the Pertronix website.

Prolly doesn't help since I can't get mine to run!

Paul

I'd try it with the tach adapter wiring completely disconnected just to see if it changes(grey wire from box not connected at all), and then maybe try to get another box to plug in and test. Maybe test that box in a different known good car running a similar setup. Sounds like the other components are good.

I'm assuming the wires you reconnected for the cylinder select were matching colors?

Sounds like a good plan.. And yes matching color for the wires.

Also check and see if the rotor has a resistor in it. Need a zero ohm rotor to prevent arcs causing misfires.

Ben - couple of things to try:

1) maybe the Petronix isn't triggering the MSD correctly - if you have an oscilloscope you can check the waveforms? failing that, drop in a set of points and wire to the MSD per instructions and see if the engine running improves

2) how does a timing light check on the crank pulley (or flywheel) look at lower revs? Consistent flashes or are there bogus or dropped flashes?

3) The MSD needs a solid GND and battery feed; these boxes demand high current at high revs. Make sure the supply isn't fed from tiny wires?

- Tony

I will check all those things.. Wiring is all new as Perry made the harness from the MSD harness and integrated it to the brand new engine harness..

Super frustrating for sure as the engine was known(dyno sheets etc) and we changed nothing except the msd is from the 4cyl set up.

Called MSD this morning.. They feel I should isolate the wiring from the pertronix along with the coil wires to ensure no mixed signals.. Thoughts on that?

It would be interesting to see if that makes a difference. In the manual it says to route the coil wires separate from everything else to reduce EMI to the box. May be worth rigging something up temporary to see if it works. How tied in are all the wires in the custom harness?

They are completely integrated.. I may have to just use a different harness and make home runs and see what happens.

..kind of what I was suggesting? Temporarily take the Petronix out of the equation to see if MSD + 6 cylinder work.

- Tony

I suppose it is. I will report back.

I dont think its a pertronix problem, its the bundled wiring..add some leads like the directions above,,all mine are that way no problem..

So made home runs with the MSD harness and everything works as it should.. Crazy.

Sounds like it was interference from having them all bundled together then? Makes sense with how much is running through some of those wires.

I guess so.. Probably is to make it look nice now.

That's the fun part!

Good to know you got to root cause though.

- Tony