Make sure there is a braided ground strap from the main body to the hood.
I have seen a lot of these vehicles where that hood ground has been taken off or rusted connectors
If it is there make sure the contacts are clean

 I  have a 1980  CJ5 Jeep, with V8 engine.   I have very extreme ignition
 noise, of course on am only. Fm works fine.

 I have replaced the plugs, and later installed high quality, carbon core
 plug wires.

  What other efforts can I try to get rid of this ignition noise ?

 Thanks !

 James

If it's only on AM, chances are your antenna's ground is bad, probably
corroded or rusted.  Possible that the deck itself has a bad ground or
that the antenna cable's shield is loose at the deck connector, but my
money would be on checking the antenna's ground first.

James;2291595 Wrote:

We have a flowchart that helps you narrow down the possible sources;
try it: http://caraudioforum.com/flowchart/, it helps.