Low oil pressure

Have you had a mechanical gage put on it? Perhaps there is an intermittent electrical problem between the sender and the gage (perhaps a corroded and/or loose connector terminal) or in the gage itself. The mechanical gage would bypass such possible problems and confirm whether the pressure itself is truly fluctuating or if it is erroneous gage readings. If you aren't getting any indication from the engine that the pressure is truly dropping to zero (valvetrain clatter, etc.), you might just assume an electrical cabling or gage problem and troubleshoot it accordingly.

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')