Ignition failure when hot

[sputnik 440]

I have an MSD 6AL and an MSD pro billet distributor. I recently rebuilt the entire valve train and put in a new cam. When I took it out for the first time, it ran fine until it got hot. It is a 440 HP with 560 - 590 HP. The engine compartment gets very hot because of the headers. The wires (2 of them) that go from the distributor to the 6AL got too close, touched, the header and it melted the wire and shorted the distributor. I spliced, soldered and wrapped the wires in that section. Now, every time I take the car out, the engine either stops abruptly, or starts really missing. Assuming it is an issue with the wire that melted, can I replace that wire (the two of them) and splice in the two prong connector and splice in the wires 3 inches from the distributor? Will the change in impedance cause a change in the input to the distributor? Might I have another problem?

 

[Jcharger]

The wires from the distributor transmit the signal to the MSD so it will know when to fire. I would look to them first and assume you can replace, or rewire them. I do not know if MSD has the parts but that might be worth a check.

As another thought, I had an issue of running crappy when warm. It would miss. The issue was the coil. It worked fine cold, but not after putting it under load.

 

[Darthomas]

You can get wire with a woven cloth fiberglass insulation specially made for high temperature applications.
With headers right there, it would repair and prevent the issue.
The wire could lay right on the header, and never care about it.

 

[eric383]

If you are just splicing the wires you will not change the impedance that much as long as your repair is solid. I guess there is always a chance that the shorted wires caused a problem in the 6AL, dist., or coil. If you are still having the problem I would try eliminating the 6AL assuming the dist. can be run without the box. If you still have the old points dist. you could try running that with the 6AL to eliminate the MSD dist. This will be a process of elimination to find the problem.
Good luck.

 

[sputnik 440]

If you are just splicing the wires you will not change the impedance that much as long as your repair is solid. I guess there is always a chance that the shorted wires caused a problem in the 6AL, dist., or coil. If you are still having the problem I would try eliminating the 6AL assuming the dist. can be run without the box. If you still have the old points dist. you could try running that with the 6AL to eliminate the MSD dist. This will be a process of elimination to find the problem.
Good luck.

Not the solution I was hoping for, but one of the possible causes. I think I will contact MSD and see what they suggest doing. My thought is to rewire the MSD distributor to the 6AL. I'll try that first.

 

[sputnik 440]

I know how to test the coil for ohms. Will that show me it is week, or do I have to test the output under load? How would you do that?

 

[Jcharger]

I know how to test the coil for ohms. Will that show me it is week, or do I have to test the output under load? How would you do that?

For the issue I had, my coil looked OK (ohm wise within spec) when cool. I never checked it hot, but I know that replacing it made a miss go away. For what it is worth, the MSD tech line reply also said there were sometimes issues with Aluminum head engines related to grounding of the heads. My hope is that your issue has to do with the wires on the pickup from the distributor. They only send an A/C signal to the MSD box so I do not see how shorting them out would mess up the MSD box. I also don't see how shorting them would mess up the sensor. You can check the resistance across them and see if that is in spec. I don't know what it should be, but guess that can be found out.