81' SC - Oil System Flaw - Over Flooding Engine

[Qcurtis88]

Hey there, this is my both my first Porsche, and subsiquently first forum post, so bare with me!

I recently purchased a 81 911 Targa. Had a PPI and all the major checks passed with flying colors. Still had an aircooled specialist put some work into it to make sure she was roadworthy. Had new oil lines, brake lines, tires, pads, plugs, air filter, oil, etc etc. The car really came alive after the work and I was thrilled.

Put about 1k miles on it since and the car ran amazing! Until...... I ran it in the canyons for a an hour or two, temp gauge never passed the 9 oclock point (great). But then I came to a stop for a minute or two with the engine running, and then when I started back up the car turned into a james bond car and left a MASSIVE smoke screen out the tailpipe (no where else). I quickly shut it down and called a good friend. He suggested oil sometimes accumulates in the heat exchangers and its just burning off, no biggie.

I started it back up and after 30-45 more seconds of pure smoke, it burned off and stopped. Weird, but hey all good, kept going and car ran perfectly. This then happened 6-7 more times on my way back from malibu, and it was ALWAYS when the car came to a rest for more than 30-45 seconds and then set back.

So few things I've ruled out:
- It's not overfilled. I've checked this multiple times the proper way, that isn't the issue
- The smoke is coming from out the tailpipe and nowhere else so this isn't an issue of oil leaking onto the exhaust or anything like that
- Gas isn't getting into the oil
- Engine has never overheated or even come close (never passed 9'clock)

Few ideas:
- Seems like the oil system is continuing to send additional oil to the engine as if its under load, even when the car is idling (and doesn't need more oil). This in turn is filling the engine and intake with oil so when it starts off again it turns into a james bond smoke screen. Once it's burned off and the car is moving, everything is fine as the engine is able to handle the additional oil.

Could this be a faulty thermostat? Could it be getting stuck open and not closing when it should? Or is there another valve or gauge that's not realizing the engine is off the power and isn't closing the additional oil tank off? The oil on the dipstick has air bubbles in it (cavitation?). Not sure if this helps indicate an issue or leak of some sort but figured I'd mention it.

I've talked to specialists and looked at forums, and it doesn't seem to be a very common issue.. if anything the engines overheat with a faulty thermo, so this one is weird as that's never been an issue, and it's getting too much oil at times.

Any thoughts or suggestion in troubleshooting this would be appreciated!