cummins 400 big cam 3

Like JP3 said , I have had this with worn valve guides.
The guides don't have to be worn but it makes it worse.
At idle there is actually a negative pressure in the intake manifold as apposed to a positive pressure when the turbo spools up.
This effectively sucks oil down the guide and in to the intake very slowly.
As soon as boost comes on it is forced back.
If you idle for long periods there is enough time for some oil to get in to the intake manifold.
When you then rev up this gets in to the combustion chamber and can cause blue/white smoke.
As soon as its burnt off it goes away.
If it is excessive check valve stems or guides for wear.

 

I've been reading this thread with some interest. I have a Cummins 350BCIII, and last fall it seemed to run just fine albeit for the leaking injector pump. I switched the injector pump over the winter and now this spring I have a sort of miss as it revs up.(the truck did not run much for about 6 months) after a few secs at 1500 r's it seems to clear out and plenty of power. some smoke with this engine is normal as it is not new at all. Now with that said, I set injectors and valves as well today with no change in smoke, when I reved it up after warm up and held it at 1800 r's for about 30 seconds I could hear a slight fluttering in the exhaust from what sounds like one cylinder but not like it was missfiring. the fluttering was intermittent. When I wind up from a time idling (about 3-4 minutes) I get this sound like someone is hitting my valve covers with a hammer and it too clears as a few seconds of higher rpm's pass. Could this all be symptoms of what was being described in this thread as well? maybe time for new guides? I've been using some injector cleaner as well and as of yet I haven't seen much inprovement. Any thoughts would be greatly appreciated.