Modern stereo. static scratchy sound when running

[FSHTAIL]

So I bought my 73 Cuda in January. 
Had an aftermarket modern Pioneer deck..      it worked decent when the car wasn't running. 
When running it sounded scratchy and static like no matter what I used.  CD player mostly.   

I wasn't a fan if the stereo so I installed a new Alpine stereo.

Same results.       
Works great when engine is off, static city when running. 

MSD 6AL
MSD 8.5MM wires.   

I'm going to try a different grounding location.   
Any recommendations?

[Shane Kelley]

You can try different grounds and that may help. But I will tell you it's hard to correct with the MSD ignition. Even worse when use a amplifier. They sell a filter that goes in line with the power wire. Those help sometimes. My recommendation is a bigger cam and nice exhaust. That will be all you want to listen to. 

[Chryco Psycho]

You are obviously picking up RFI from your ign system You could try shielding the deck in tinfoil

[Bullitt-]

article on MSD & RFI  https://www.hotrodhotline.com/content/radio-frequency-interference-article-msd-ignition

[Cuda Cody]

Welcome @Chris Pauluk     

This might not be the solution, but it could be something similar (Click on Radio Noise under TSB's):

https://www.e-bodies.org/resources/cuda_challenger_tsb_specifications_engineering_illustrations_drawings/
Direct PDF Download:
http://www.e-bodies.org/Resources/TSB/Radio_Noise.pdf


Also check out  73-3  : Radio and Sound System Troubleshooting:
https://www.e-bodies.org/resources/master-technician-service-conference-reference-books/

That might have some good tips to try.  Good luck and let us know what you find.

[RUNCHARGER]

I agree with Shane, Dynomax Ultraflows!

[FSHTAIL]

Voodoo cam and Magnaflow exhaust is just fine for me..          
The side routed AAR setup had to go tho.    I drive the car a lot..

My MSD 6AL is mounted right behind the ashtray..

I'll have to try that capacitor setup.   
I already bypassed the ign and have it direct on a kill switch..     

[Shane Kelley]

Voodoo cam and Magnaflow exhaust is just fine for me..          
The side routed AAR setup had to go tho.    I drive the car a lot..

My MSD 6AL is mounted right behind the ashtray..

I'll have to try that capacitor setup.   
I already bypassed the ign and have it direct on a kill switch..   

Well the good news is your cam is Chryo approved. The bad news is I doubt you get that noise out of your system with the MSD sitting right by your stereo. You might try relocating the MSD box away from the stereo. If you want it out of sight under the battery tray is a great place to mount it.

[FSHTAIL]

Are these boxes waterproof?

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[Shane Kelley]

They can go under the hood and be fine. Just don't drown it if you wash engine compartment or submerge it. That's usually where everyone mounts them.

[FSHTAIL]

Any pictures of under the battery mounting?

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[Shane Kelley]

Notice I used countersunk screws down in the channels so the battery doesn't ride on the screw heads.

[Cuda Cody]

Very clean and nicely detailed engine bay!   

[FSHTAIL]

I undid all the garbage wiring the previous owner did.   
The msd was grounded through the firewall to the intake manifold, the power wire was wired to the starter relay. 

Wiring through un-grommited holes in the firewall. 
This was a rats nest waiting to ignite.   

Stereo works great and msd box is under the battery tray.     Great spot for it.     All the wiring reaches perfectly. 

3 out of the 4 isolators are on it, she's solid. 

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