Digital 6A - Radio snap/pop after change to HEI from points.

[mooser]

Over the winter I changed from a GM points distributor with a Digital 6A and Blaster 2 coil to using an HEI distributor with the same Digital 6A box. I removed the guts of the distributor and installed the wire harness to the 6A and changed the stock coil to the MSD in-cap coil (no room for the Blaster) and put on a Street Fire rotor & cap. Following the instructions with the coil I put in the low resistance button from last year (hardly any miles on it really). Ran the distributor center ground wire down to one of the bolts that was holding the original coil to the intake. Box was wired direct back to the battery with the MSD capacitor a few inches away from the box. Box is located behind the passenger wheel well several feet from the radio, but of course the radio is near the distributor (but down on the trans hump so not right behind it like on some cars).

Wires are Taylor Spiro-Pro, virtually new. Car seems to run fine, starts good, etc., but I've got a bad snap/pop/crackle on the radio now that wasn't there before. Happens regardless of the input (FM, CD, USB) and isn't a buzz that goes with the RPM just random snap and pops almost like you had a loose wire or something. The changes from last year were only the distributor which is really only the pickup button and coil as everything else is using the 6A box. Before I start randomly swapping parts, anyone have a logical test sequence they could suggest? I'm going to start with the coil ground wire to the coil frame as it had a black coating on it that maybe wasn't removed from the bolt eyelet, they maybe swap in the stock coil. After that I'm out of ideas. Thanks, M

[mooser]

Check ground to the coil, tested fine (zero Ohms). Swapped coils from the MSD to the stock HEI, still snap & pop. I might have to put all the guts back into the distributor and try without the 6A box (but the box worked fine last year with the points distributor). Can't see how it could be the pickup coil or why it wouldn't be a consistent tick, tick, tick if it was rather than the sporadic snap that I'm getting. No input from MSD tech, so I guess this is an odd situation. M

[mooser]

Another update? Pulled the radio out, checked grounds, swapped RCA cables, etc., with no change. Pulled an old HEI distributor from my brothers place and was about to swap the entire distributor to test, before doing that I just stuck the old cap onto the existing distributor and there was no snapping. Put the MSD one back on, snap crackle pop, put the old one on, no noise. Put the MSD coil into the old cap, no noise. Put the MSD low-resistance button into the old car, no noise. Put the coil and button into the MSD cap, snap crackle pop. Put it back into the old stock cap, no noise. Anyone want to tell me how the Street Fire cap can cause snapping & popping in the radio? M

[mooser]

Bought a new MSD cap (red, proper HEI cap) swapped it in and same problem. Snap, crackle, pop on the radio, put the old cap on, no noise, or at least it ran for several minutes without any snap crackle pop. Rechecked all the plug wires, tested with Ohm meter and they all seem fine, plugs look fine, just can't use MSD caps it seems. Ah well, another fistful of money down the drain. M