PastorMatt - looking at your post concerning the 45 minutes of idling:
(1) Changing the main jet will have ZERO bearing on the idle calibration; only on the main metering circuit calibration. At this point, DO not change to a smaller jet! You should have received the correct main metering jet in the kit you used to rebuild the carburetor.
(2) Your last post indicated the engine was running fine. Nothing wrong with having someone with the tach, timing light, and vacuum gauge to check things; but at this point in time, I would suggest taking the truck for a drive. Close to home at first, to develop confidence in the reliability; but if no issues, a 20~30 mile trip at highway speed should tell you a lot.
(3) The comment about checking for carbon fouling after 20 minutes at sustained speed is true; PROVIDED THAT YOU SWITCH OFF THE ENGINE AT SPEED, COAST TO A STOP, THEN CHECK THE PLUGS.....NO IDLING!
Not to attempt to muddy the waters further, but a comment hopefully for understanding:
In "carburetion 101" one learns there are three major methods of improving the fuel/air atomization: (1) add heat, (2) add air velocity in the carburetor, and (3) add fuel.
What stands out in the above statement is that if the heat is constant, then adding air speed will allow reduction of fuel in the fuel/air mixture. So the fuel calibration will be more concentrated at idle (low air speed) than at higher engine RPM's (greater air speed). Not at all uncommon for 5 minutes at idle on a properly tuned engine to show some carbon on the plugs.
Stay with it!
Jon
