So for whatever reason last year I added a MSD box to the ignition and over the winter I swapped in a HEI distributor with tach drive.still using the MSD box.

Runs fine, really bad snap crackle pop on the radio when I took it for a drive
Not an ignition whine, random snap pop every few seconds as it would be with a loose ground or power on the radio

Checked all the wiring, seemed ok

Put the module back into the distributor and removed the MSD box... same thing snap snap snap

A new streetfire cap and MSD coil came in, installed, same thing, actually slightly worse

pulled the radio out and checked all the wiring there, disconnected my new digital PRNDL and the Ipod etc JIC, nothing

Today I pulled an old stock HEI cap from my brothers place, something salvaged of some POS that was scrapped at some point, put it on, no snap crackle pop
put the MSD box back into the circuit with this cap, no snap
put the MSD cap back on, snap crackle pop
Old POS cap, no snap
put the MSD coil into the old cap, no snap
put the MSD low resistance button in, no snap

put the coil and button into the MSD cap, snap snap snap

WTF? somehow the Chinese cap and the MSD cap both let this thing snap crackle pop the radio but the old stock crappy cap seems to work fine?

I'll drive it for a while with the old cap to see but so far it seems to have solved the issue

Ah well, we do this a a hobby cause it's fun

M

 

I did following on a circletrack car

You CAN use the big cap HEI as a DISTRIBUTOR ONLY. Big Cap gives you wider spread between sp terminals; less Xfire.

eliminate hei Module entirely, eliminate the hei coil

Use HEI's pickup as trigger for MSD box (e.g 6 series)

Use a REMOTE / EXTERNAL coil like a Hi Vibe Blaster canister or HVC ... any remote rated for use w/ your MSD box

Use a remote coil adapter msd pn 8401 atop HEI cap (msd used to sell em, think mallory did too) ... gives you A CENTER COIL WIRE TERMINAL TO ROUTE TO REMOTE COIL

Use a top-grade cap & rotor.

 

That's what i have / had. Only the pickup is still being used, had the adapter cap with the external coil, didn't 0like how it worked out so went to the coil in cap instead.
Just the weird problem with the msd cap which i bought to make sure it was "GOOD" lol
M

 

No personal knowledge of Msd caps and other Msd products being made across the pond but I bought an Msd cap for a GM points distributor that lacks the little square lug that locks the cap in place. It just does not fit like an Ac delco or other makes of points caps. Plus it lacks the adjustment window. Not worth the money! Looks cool though!! I found some USA made caps from SMP and Delco Remy on fleabay.