First pilot logbook entries for homebuilders

This may seem a silly question and it probably is, but has anyone entered first engine start and taxi time in their pilot logbooks prior to first flight? I'm dying to record actual operating activity of my RV-8 in my logbook, but not sure it's appropriate if no flight is involved. I do have an "A/C Familiarization" in my customized logbook; maybe I'll put it there with no takeoffs or landings recorded but total time included. Thoughts, anyone?

You can put whatever you want in your pilot logbook. The only question is what you can count toward a higher rating or license. Some of your entries might be for memorable reasons, but if there is no intention of flight, you shouldn’t log it as ‘flight time’ that you would count toward a rating, or training/insurance flight time requirements. Putting actions and experiences in your logbook is a good way of memorializing your flying life for future reference in my opinion.

I log every hour the engine is turning. This includes run ups to check for leaks after Condition Inspection and oil changes.
Like Scott said, you can put anything in the logbook you wish. I know some that log a few minutes if they get the opportunity to “fly” someone else’s airplane while riding as passenger. That way they get lots of different airplanes in their logbook. It doesn’t count for anything official but is a historical record for themselves.

One caveat to "put anything you want in the logbook": if you ever apply for another rating (say, ATP or something), you're supposed to *exclude* any time that was not with the intention of flight from the 8710/IACRA, since for experience for a certificate there *are* specific rules (14 CFR 1.1: "Pilot time that commences when an aircraft moves under its own power for the purpose of flight and ends when the aircraft comes to rest after landing") - so you can save yourself the trouble by just not logging ground runs.