Timing Chain Stretch @ 25K

[garysleeman]

My used 6.2 w/25k starts fine and runs good cold. When the cold advance switch opens the motor runs rough and spews white smoke. I've put a jumper wire to the cold advance. I checked compression when the motor was warm and all the cylinders are 380 pounds. The motor was taken from a 1/2 ton pick-up used to salt parking lots at St. Lawrence University. They must have loaded the truck down pretty good because the rear end, transfer case and clutch showed signs of rebuilds. Given the history of the truck could the timing chain be stretched with only 25K miles?

[rhill2901]

Sounds like you need to advance your timing some. Try moving the pump to the driver's side about 1/2 the width of the scribed line and see if that clears up your rough running when warm. Getting it dynamically timed would be more accurate though.