Recently bought a 3rd gen IROC convertible with some known issues. The main being that it is smoking out of the exhaust. My mechanic works as a diesel mechanic during the day and moonlights a few nights a week on cars. It's been 100 degrees here for awhile now, and his shop at home isn't air conditioned, so he hasn't been doing much on it yet. He is going to do a compression check soon (oh, and I forgot to mention that his sister is having a baby today), but it may not be until next week. I'm racking my brain with what's going on. Engine idles smooth, runs extremely well, and has plenty of power. Exhaust smoke is whitish, with a smidgen of gray in it, and dissipates rather quickly. At cold start, it smokes ZERO, but as it warms, it begins to smoke. There is no antifreeze in the oil, and no engine leaks (but it is a 1/4 qt. down after 200 miles, so obviously it's burning some oil). Would a bad piston ring cause it to smoke only after warming? Could a bad Intake manifold gasket possibly be the culprit? Blown Head gasket I've almost ruled out because I'm not seeing oil contamination and it makes good power. Anyone had a similar problem or know what may be the issue?
Thanks.

 

Valve guide seals

 

Read your post and throw a dart at it. Before you start wildly guessing at a problem, have some basic diagnostics done. Compression test and leakdown test are the first things to do before continuing.

 

The compression check is coming hopefully this weekend, I said that in my post. It's just been worrying me sick if it is indeed a piston ring issue, so I figured I would check to see if anyone has experienced the same problem. Trust me, the engine isn't getting pulled unless it's a bottom end issue.