I advanced timing to 15.5 {i thought}about 4 months ago but noticed lately when I bog it i get grey smoke and not black smoke. im not trying for smoke but when i first noticed it i thought it was because of 40* weather. today was 60-70 and i purposely layed into it and gobs of grey. my boost still powerful 35 lbs and it might be running hotter egts than normal by say 100* . it still is peppy and gts up and goes. starts instantly on 30* days and cranks 1< second before starting. i think maybe from get-go i didnt set timing right but other than grey smoke it runs fine. any thoughts?

This is a good one for ISX to answer...

If it is truely grey (not light black) I think you might have a leaky injector. Black is partially burnt and white is unburnt so a mixture (grey) would mean you are getting some black smoke from some and white smoke from others. At low RPM bogging it, it becomes harder to get all that fuel burnt on a crappy injector. At higher RPM it can probably burn it all if the leak isn't too great. I think EGT might just be an effect of the timing advance. When you advance it and lug it, it is running way out of it's optimum range so it fires the injector before it should creating a sort of cylinder backpressure sense which in turn raises EGT. Mine had grey smoke and I recently found I had an injector that wasn't popping at all, it would just force the fuel in like a hose rather than a mist. Other than that, it would be something else that would cause unburnt fuel like valves way out of whack (doubt it).

Can valves be way out of wack with 350k miles and never a valve adjustment? That's my work truck, 92 ctd and has light grey smoke but not real bad.

Can valves be way out of wack with 350k miles and never a valve adjustment? That's my work truck, 92 ctd and has light grey smoke but not real bad.

man i bet that thing is noisy!

Not bad after adding a quart of TCW 3. Truck still runs like new, except that 12 valve can tell a difference between brands of the 2 cycle oil.