Ever since I got my 80 a few years ago it has had a dull knocking sound when I first crank it. No it's not the rattle, my dad's 95 use to do that but mine is what I would call a dull knock and its not as loud as the rattle. It only lasts for maybe 2 seconds and is usally during cold starts, or sometimes even after a quick stop at wally mart. I've had an engine spin a bearing and this is nothing close to the rattle/knock of a bearing, I want to say it sounds like a cam lobe that isn't getting oiled right away. Don't think it matters but it's got around 85k on the clock.
