after my 91 NA's (with 220k miles) been sitting for 2 or 3 days in cool nights (it sits outside) I get a oil smoke from the exhaust for 30 seconds or so. This started happening recently. I've checked the plugs and they look good, so whatever oil coming in isn't enough to junk them up. (however my emission test from 6 mos ago had twice the level of HCs as 2½ years ago)

My first (and cheapest ) thought was that it might be the oil nozzles malfunctioning. Someone told me that it's almost never just the nozzles, but the OMP, or of course the engine seals. Aren't the nozzles little valves or something like that..why aren't they the culprits?

If a compression test is done and the results are in the 80 psi or above range, can bad seals be ruled out?

Or is it possible the seals would "relax" when the engine is off and the weather is cool (40s °F at night), allowing oil in, then tighten up again once compression starts? Though that theory wouldn't explain the emissions HC increase would it?