Hey guys,

Have had a slight noise progressing over the last few weeks, sounds like a slapping noise when accelerating, today the slapping got worse and there was a smoke cloud out the exhaust.

The engine still runs but is idling atlittle rought, but @ 2000rpm it sounds fine

Any ideas on whats happening or how serious this is? or what could be the cause of this?

The 4.3vortec is not really well known to me, as ive had 3.8vortec's, but never a multiport 4.3

 

almost sounds like piston slap. That happens when there is too large a gap between the piston and the cylinder wall. What color is the smoke?

 

Hows the oil pressure & level? Have you checked vacuum lines for leaks? A video with sound or just sound of it might help too.