Ignition help I think?
 

My car is a C/SA 1970 Chevelle L78.
I am looking for some help with an issue that I can’t figure what else to do next.
It started in Spring of 2022. The car was running well. Then my MSD Digital 7 Programable 7530 stopped working. Since it is potted, it was unrepairable and trashed.
I replaced it with an MSD Grid. The first time I started it up, it was fine. I turned it off and then it wouldn’t start. I sent both the Grid and the ignition box back to MSD. After some time they shipped me both pieces back new. I then installed the new boxes.
After that it ran OK but it had a miss that made me crazy. I sent the boxes back in to MSD. They replace them again. I reinstalled the boxes.
The rotor, cap and spark plug wires were replaced. MSD personal were at the race and they completely looked at the system. They gave it their blessing.
I was still chasing inconsistent misses. I then took it to my local race shop. They found that the Grid box negative ground was never crimped from the factory. It pulled right out of the connector. We checked all the other parts of the ignition wiring. At that point, I thought my problems were over.
I went to a divisional race. The car was really slow. It would barely run the index. It was slow at the 60 foot by .1 to .2 slower than usual. The MPH was down by 7 MPH. This car usually runs .7 to .8 under the index. Overall it is slow and The RPM fluctuates in third gear.
I brought it back tp the speed shop. We put in a 16 volt system. I checked the compression. All cylinders were within 5 pounds of each other.
I thought that maybe the sprag had gone out. I replaced the torque converter. I went back to the local track. No appreciable change.
I got frustrated and replaced ignition system again with another new Grid and ignition box. I also replaced all the ignition wiring.
I then went to the next divisional hoping that the ignition would fix the problem. In the test and tune, no change.
I have sent the Racepak runs and the MSD Grid Review runs to MSD. They told me that they saw nothing unusual. I tried a run with the tachometer disconnected.
I have heard many times the gripes about the Grid. How much you hate them. Most people have no problems with them. I am not looking for your opinion about the Grid.
I am looking for places to investigate and try to fix my car.

Re: Ignition help I think?
 

where are you located

Re: Ignition help I think?
 

Do you have a known good HEI or even a dual point that you can put in just to see if that will make a difference?

Re: Ignition help I think?
 

First place I go is to the crank trigger pick up and related wiring.

Re: Ignition help I think?
 

Run the engine on an engine dyno to make sure it's not something in the car. Also use a basic known distributor, coil, and ignition box.

Re: Ignition help I think?
 

I know this can be very frustrating. Just curious, did you do any welding on the car before all your problems began ?? :)

Re: Ignition help I think?
 

The pickup wires could be reversed.
Replace the ground wire.
Power and ground wired directly to battery.
If distributor is locked out, check phasing in the cap.

Re: Ignition help I think?
 

Sorry for your problems.

People have chased what seemed to be ignition problems that turned out to be carburetor or fuel injection problems.

Re: Ignition help I think?
 

Southern California

Re: Ignition help I think?
 

Factory wiring will not let the pickup wires to be reversed.
Ground and positive are directly to battery.

I will check the phase in the cap.