Ali Vette

Hi everyone, I searched but couldn't find the right fix for my issue.

I have a '71 that I installed an HEI on and everything was fine with the old stereo (not original but old).

Last week I put in new autometer gauges in the center console, converted over to an electronic '76 tach and ran tacho wire from HEI to the tach with the tach filter inline (haven't grounded it yet though) and also single din stereo.

When the engine is off there is no noise whatsoever and the stereo sounds perfect.

With engine on the stereo makes popping/ static like cutting in and out noises and gets worse the louder you turn it up, seems to happen worse at idle also. also with the stereo off and engine on, you can hear noise coming through the speakers I think (will check this again).

So I got one of those power noise filters and put it on the power line to the stereo and it didn't do anything. I also tried a direct power line to the battery and it cleared it up some but not completely, so I think something is making the power signal dirty in the car, like the ignition, or something affecting the power line, maybe due to HEI.

I cam across this thread:
https://www.corvetteforum.com/forums...er-repair.html

and it has a picture showing a radio noise capacitor on the power line to the distributor, not the tach line.... I don't have one of these cause obviously my 71 never had HEI, and per threads here I just ran a new wire from the fuse box IGN to the HEI distributor for power direct.



It seems like this would help my issue especially since its labeled "radio noise capacitor". where can I get one of these guys, I don't read that people are using them but it seems I need them, I couldn't find it online and I don't think they are talking about tach filter cause its on the power line in the diagram.

Also is there supposed to be a capacitor/filter on the alternator cause my car does not seem to have one, I think Bubba had a hand at some wiring in the engine bay at some point so trying to put all the stuff back in place. I don't have alternator whine though, its def a popping sound.

anyone have any insight on this capacitor and where I can get it from pls let me know, first time working on vettes and never seen the '76 setup where all this stuff comes from, thanks!

MelWff

what kind of plug wires are you using with the HEI?
are you using resistor spark plugs?

Ali Vette

I bought these wires off amazon, they say spiral wound and RFI supression.. although reading it again it says ultra low resistance
Brand New Dragonfire HEI 10.5mm SBC BBC Spark Plug Wires Complete Set PW350-DF

I wonder if I can try my old wires if they will fit, it wasn't the original dist on there the one I took off was a Mallory with a separate coil.

I am using these plugs, they say resistor on them
NGK IRIDIUM IX Spark Plugs UR6IX # 7348

In another thread I was told to put the ignition shielding cover back on, I thought it was just for show I removed it when I redid the intake gaskets and put the new distributor on. I will be trying to put it back on and see how it goes. I don't have the curved covers for the plug wires hopefully the top shield will do most of the trick.

MelWff

looking back at your first post you say you havent grounded the tach filter so it's not doing anything.

Ali Vette

Yeah I am going to do that also, when I installed it I had originally grounded it but then I couldn't fit the dash pad on properly so I removed it and let it hang, will ground it and see how it does but I thought it was just for the tach and not something that would mess with the stereo.

So I am going to ground the tach filter, put the ignition shielding back on, and put the noise filter I bought from the car audio shop on the power line and see how it goes.

I hear people saying to put a choke filter on the power and ground lines also, the kind I have is more of a capacitor I think, so I might grab a pair of these also just for extra insurance.

Ali Vette

So the issue is finally resolved... installed a flame thrower ignition tune up kit in my knock off hei distributor and all the noise went away magically. It came with a new ignition filter and everything and car seems to run better, sound better, and no radio noise. Super happy about the outcome, just wanted to update for those who may have a similar problem install a good kit in there that worked for me.

7T1vette

Thanks for the update, Ali. Most folks either get the info they want and fix the car...but never report back. So the rest of us never learn anything new from that effort. Or, they do NOT fix it and they end up selling their car.

With your feedback, we now know what will work in this situation.

Thanks.