I'm putting the new ignition in the car, and as per the instructions, the MSD will not work with a tach filter. So I can't find the dam tach filter location on the 1990, as I need to cut it out.

SO

2 questions:

1. is there a tach filter
2. WHERE IS IT?

Thanks.

Thanks VetteOz, I looked but I'll try again. didn't see it the first time.

I appreciate your patience.

Do you know what color the wire is that goes into the harness? I can interrupt it there, could be easier.

went down again and found it.

I'm just going to pull out the oil pressure switches and make it easier to get down there.

It's TIGHT to make connections.

Looks like a black/yellow wire. Is that it or is it dirty. If I can pull it out of the harness will be easier to make the connections.

Thanks VO. I think what I'm going to do is cut the plug off the capacitor and attach it to the MSD box and just plug it back into the harness. Seems to be the easiest and cleanest solution.

For whatever reason the MSD literature says it will not work with a tach filter. They say specifically not to do it.

I am going to hook it up to the tach filter first, see what happens, then if it doesn't work, I'll bypass it.

Thanks VO. I think what I'm going to do is cut the plug off the capacitor and attach it to the MSD box and just plug it back into the harness. Seems to be the easiest and cleanest solution.

For whatever reason the MSD literature says it will not work with a tach filter. They say specifically not to do it.

I am going to hook it up to the tach filter first, see what happens, then if it doesn't work, I'll bypass it.

I think the posibility with the tach filter in place is you may see the rpm drop to zero under certain circumstances. The function that the tach filter does on the stock signal output from the HEI is internally handled in the MSD when it output the "cleaned up" square wave tach signal.

i think the posibility with the tach filter in place is you may see the rpm drop to zero under certain circumstances. The function that the tach filter does on the stock signal output from the hei is internally handled in the msd when it output the "cleaned up" square wave tach signal.

exactly!