Have a '51 Chevy that I converted to 12v. I installed an MSD 6a ignition box and now the engine just dies. Put a timing light on it and it shows good spark then nothing, cars starts to die then spark starts again. It is sporadic with no rhyme or reason, just misses a few beats with no spark at all. I'm using the original ignition key switch could this cause a problem since it is just the on/off with no accessory? Since it's left in the "ON" position at start could this be the issue? It has progressively gotten worse to the point of almost no spark at all just an occasional blip. Could the Ignition box be overheating as I have it tucked in behind the gauges in the dash? Any help would be appreciated
If you wired it correctly, it should be getting power from the battery, and the ignition switch connection is just a signal to "turn it on". But you could put a test light on that connection at the MSD and see if it is getting power from the switch, when it's acting up. I don't know why you think an MSD box is necessary or helpful on a car like that...but I'm assuming it's still the original six, which will work fine with points and a coil.
Is it a brand new MSD box or used? if there has been any welding done on a vehicle without it being removed it can be damaged to varying degrees. There are several diodes inside. if just one or two are damaged the vehicle may start up but not run well. Years ago I sent one out to MSD for repair and that's what they told me. The good news it was like $40.00 at the time to go through it.
I concur with Jim. An MSD box is an excellent system for high performance engines, because it increases the available voltage and current for ignition. The type of system that would be more suitable for your application, is a capacitive discharge ignition system. This type of system, such as the Delta Mark 10, increased the available voltage but reduces the current in the primary side of the system, where the points are located by a factor of 100. That means, that instead of having 2 amps being switched by your points, you only have .2 amps going through the system. This increases reliability and lengthens the life of the points. In the mid 70s, most auto manufacturers switched to an electronic ignition system, which eliminated the points and also increased the secondary voltage available. This reduced the market for CD systems, and many companies moved on, but you can still find the Delta Mark 10 systems on epay. and probably at swap meets. So, your two choices for a more efficient system are, to find a Mark 10 CD system, or convert to an electronic ignition by adapting a mid 70s distributor, from a Chevy 6, to your early engine. Without comparing distributors, it is impossible to know how easy or difficult this would be. Last point, with these systems it is necessary to use high quality spark plug wires.
Visionary, I did tack up my exhaust with it hooked up. Grabbed a Procomp ignition box from my buddy and everything works fine. Thanks everyone for your help
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