Hard start after long runs...and a hypothesis

[mnewport]

Amazingly enough it's been such a mild winter here in Chicago that I routinely find myself driving my SC instead of keeping it stored away.

Because of this, I'm reminded of a problem I encounter from time to time: after runs of an hour + in length, I find the car is very hard to start (if not impossible) after shutting down. Leaving it sitting for a few hours cures the issue.

Recently after thinking about it, I decided it was likely caused some sort of vacuum caused by the heating and cooling of something in the engine bay. Remembering that removing the oil cap with engine running alters engine idle, I decided to try an experiment. The next hard start issue I experienced, I popped the engine lid and unscrewed the oil cap. Put the cap back on, and cranked the engine. After doing this it fired immediately.

I've tried this several times since, and it works every time.

What do you guys think? Coincidence? If its coincidence it sure has happened a lot. If its not coincidence, I'm not sure I fully understand what conditions might be at play. Could it be as simple as alleviating what ever vacuum situation has occurred?