Have a 71 Elco. Had a AM radio, worked good, changed windshild, and the new antenna, in it is bad. So then I bought a after market antenna, and radio. Used it for about a year, was not happy with it. So I put the origanal one back in. In between this time, I changed to a HEI, and now I have engine noise, which I never had before.Any ideas how to get rid of it? One, more funny thing, is when I put on the brakes, the noise goes mostly away.

I saw an increase in noise when I switched to HEI as well....
Buy the best plug wires you can afford and use the di-electric goop!

Oh boy, a question I know the answer to! I'm normally the question asker!

Most radio noise is caused by electrical current, mostly from the alternator and distributor. If you ran a power cable directly from the battery to the radio, then make sure that the cable runs as far away from the alternator and distributor as possible.

I know this is old school but make sure you are using resistor spark plugs.