[Marty68]

[QUOTE=gvw5400;8748777]I know it seems obvious, but could it be something else? Like an exhaust leak, or even a plug wire jumping spark. The plug wire thing happened to me once and I thought it was a slight tappet noise. Even checked my valve lash and all that stuff before my buddy caught the spark jump which suprised me because I thought it ran fine. I had this happen to me on my dad's 77 K-10, he was complaining about a sticking lifter. I drove it home and you could hear it click. but in the shop I found a bad plug wire that would occasionally fire a 3" spark from the boot on the cap
to the firewall. Big cap HEI can really crank out the voltage !! I am sure the module life
has hammered by doing this.
Hope you find the problem! All the Best, Dirk[/QUOTE

it is definitely not a tick or a misfire.