Superperformance - Having engine trouble - need help

[Blas]

If you don’t see a big red box under the dash, look for an more square looking aluminum colored box. Could be he still has the original duraspark unit installed.
Blas

[rodneym]

It's gotta be on the inside of the firewall, in front of the passenger.
The cap that Pat mentions is a nice bit of insurance. I installed one, along with knurled finger tight screws and a quick disconnect(or) for a road side repair but alas, no issues with the MSD.
Perhaps the Russians?

[tortuga]

Originally Posted by patrickt

You really can't miss it. Here's a pic of mine, which is tucked neatly under the passenger side of the dash. Of course, I ain't got no SPF.... Note the capacitor. Everyone with an MSD unit should have one.

What kind of capacitor? Source?

Seems like a great idea, basically an Ac shunt if I remember from my EE100 class decades ago...

Steve H
SPF 1764

[patrickt]

Originally Posted by tortuga

What kind of capacitor? Source?

Seems like a great idea, basically an Ac shunt if I remember from my EE100 class decades ago...

Steve H
SPF 1764

MSD makes it. Part #8830 -- it's just a 26Kufd capacitor, but you have to wire it in correctly or your car won't run at all.

[tortuga]

Originally Posted by patrickt

MSD makes it. Part #8830 -- it's just a 26Kufd capacitor, but you have to wire it in correctly or your car won't run at all.

Ordered, thanks for following he tip Patrick!

[snapier]

My Superformance (SPO1400) had the same problem after 2 weeks of trouble shooting I found out that I had a faulty magnetic pickup in the MSD distributor and also a failed Control box that is just under the glove box. This was tuff to troubleshoot because both must have failed at the same time. Good luck.

[patrickt]

Originally Posted by snapier

My Superformance (SPO1400) had the same problem after 2 weeks of trouble shooting I found out that I had a faulty magnetic pickup in the MSD distributor and also a failed Control box that is just under the glove box. This was tuff to troubleshoot because both must have failed at the same time. Good luck.

It's pretty rare for two electronic components to fail at the same time without an underlying cause of some sort. Jump starts, misbehaving alternators, flaky voltage regulators, a "fast" battery charge, they can all hasten an MSD demise.

[Blas]

Poor grounding and improper installation are the major causes for MSD failures from what I have seen. Spikes in the wiring are a close second.
Blas

[tortuga]

Originally Posted by Blas

Poor grounding and improper installation are the major causes for MSD failures from what I have seen. Spikes in the wiring are a close second.
Blas

So to prevent to the maximum extent the early demise of the Msd box, should a capacitor to shunt spikes and direct heavy ground be run from the box to a very good ground? What else would fall under poor installation?

Thanks

[patrickt]

Originally Posted by tortuga

So to prevent to the maximum extent the early demise of the Msd box, should a capacitor to shunt spikes and direct heavy ground be run from the box to a very good ground? What else would fall under poor installation?

Thanks

Think. A "good ground" is more than just a fat wire going from the MSD box to the side of the block or battery. Good grounding is an overall network that provides the return path to whatever it is that is generating the source current. Here's a quiz: What is the return path of that 40,000 volts or so that jumps across your spark plug? It's obviously going to the cylinder head, but where does it go from there, why, and how does it get there? And is that path different on an MSD system? FWIW, I have my fat battery negative cable going to the passenger side cylinder head. One ten gauge wire running from that cylinder head to the aluminum firewall dashboard grounding source. Another grounding strap running from the intake manifold to the aluminum firewall. A four gauge wire running from the negative battery terminal to the chassis frame. A two gauge strap running from the driver's side cylinder head to the frame at the same point where the fans and headlights pick up their ground. And, finally, a ground strap from the transmission to the frame.

[Gaz64]

Otherwise known as a noise filter.
Absorbs the "ripple" between the supply positive and negative rails.
So the supply the module sees a "clean" supply.

[patrickt]

The answer, because I know Gaz is sitting there with bated breath, is that on our old points-based distributor, when the points open to break the ground path, and the secondary field collapses to generate that 40,000 volts, the return path from the spark plug is via the cylinder head/engine block to the negative battery cable, though the battery itself, out the positive side of the battery, through the positive lead to the primary side of the coil and back home to the secondary winding. That question will win you a free beer at your next 19th hole. Now, back in the 70's my friends and I thought of ourselves as genius car mechanics so we would test your alternator's output by pulling the positive cable off the battery, while the engine was running, and if the engine kept running then we knew the alternator was working -- what geniuses we were and, as memory serves, we just assumed that whatever alternator/regulator/ignition part that got burned up in our "testing process" was just broken before we got our greasy mitts on it. Remember, that 40,000 volts has to find its way back to the coil somehow for the car to keep running. An MSD box is even more sensitive -- and everything is running though it, including the return path of the spark (because that's the only way to get back to the coil). And that's just one aspect of the ignition and grounding process, but this will at least make Gaz happy....

[Gaz64]

The secondary is connected to the coil negative, as the points open, the magnetic field collapses inducing 400 volts into the secondary x turns ratio gives us 40000 volts.

In an MSD system, a capacitor inside the module is "dumped" into the primary, the secondary is grounded on the common negative terminal of the coil.
The spark loop is coil output tower to the spark plug, cylinder head, engine ground to chassis, to coil negative.

That's why the coil negative is the high voltage terminal, 400v on HEI.

[Moto One]

All of this is "Shocking"....;-)

Mark.

[pgermond]

Originally Posted by DownTown

Alright let me check there first and get back to you guys, thanks for the insight.

Did you ever figure it out?