Well, so much for "bulletproof" straight 6, motors knocking :(

[BIG CTY]

I'm going to expect the worst, but hope for the best here. I was driving the balls off of my rust bucket awhile ago and when I came to a stop, I heard knock knock knock going along with the idle. When I speed up, the knocking gets quicker, when I slow down it gets slower. Its not nearly as loud at idle as it is when I get in gear and go. I was running a good 75-80 for about 15 mins, RPMS were between 3500 and 4k.

Now I know enough to be dangerous, but I'm not sure where to start here. I'm kinda hoping that its something simple, but anytime I hear knocking in the engine area I get scared. Anyone have any advice? The truck is for sale and there is no way I can sell it sounding like this. Where in the he!! do I begin tracking this down?

[Chevy Fleetside]

Get a piece of hose and while it is running put one end of the hose on the oil pan and the other over your ear.. If it is a rod knock you will hear it that way and you can determine where in the pan it is the strongest.. If you hear if from down there then you need to take the pan off and figure out which rod it is.. You will need to take the rod cap off and look at the crank. If the crank is not scored you can replace the bearing.. If it is scored then you will have to have the crank machined.. If you have a machanics stethescope (sp?) then you will not need the hose..

[60-66 Nut]

It's possible some carbon broke loose and stuck on top of a piston. Try mixing a little brake fluid and water in a cup, run the engine just above an idle and pour a little down the carburator, not enough to drown the engine but just make it run rough. If that doesn't help, then you may have more serious issues. Best of luck.

60-66 Nut