273 valve adjustment???

Although this is an older thread I hope SD65 got it fixed. Adjust the valves as a maintenance item but running rich is not a valve adjustment problem. And vehicle weight doesn't have anything to do with running rich. Unhook and plug the vacuum advance and set the timing at least 10 degrees before. Then go back and adjust the idle speed and then the idle mixture. Then reset the idle speed. (the mixture adjustment will probably change the idle speed)