68 Z/28 Engine Smoking - Any Ideas?

[SuperNovaSS]

Primary float sticking?

[70 Forest Green Zee]

Since the engine was just rebuilt, I would suspect piston rings. Blue smoke would indicate some oil blowing by the rings and out the exhaust. Sorry , that's probably not what you wanted to hear.

[firstgenaddict]

How was the break in done? Doesn't sound like the rings are seated... I hope it didn't break a ring... eeeek!

[Hotrodpaul]

I would ask who did the rebuild and what type of piston rings were used, end gaps, piston to wall clearance, low tension oil rings or standard? Did they install valve stem seals when the heads were rebuilt, were the valve guides replaced, new valves, etc. How were the cylinder walls honed, what grit, on what type of machine?

Paul

[68 RS Z/28]

Thanks for the suggestions guys. The engine was done around 5 years ago so I doubt the engine builder will remember exactly what he did. I do know it was new valves. I'll check to see if valve stem seals were installed, but I expect so. I've been dreading rings as the problem....definately not what I wanted to hear to be sure. If it broke a ring, wouldn't there be other issues (noise, debris in the oil pan, etc)? If the rings aren't seated, is there any way to do this now without ripping the engine apart? I'm not a complete novice, but I confess I have no idea what the difference is between low tension oil rings and standard oil rings. Thanks again for the suggestions.

[Kurt S]

Do a cylinder pressure check and/or a leak-down test. That will tell you a lot.

[JoeG]

Check out the condition of the plugs..might be just be a valve stem seal....just a thought