Went outside to swap the oil pressure sending unit this morning.
Pulled the alternator, oil filter (which has been stuck since the build), and worked the OPSU out.
Put the new one in, with a lot of elbow grease, only to realize that I haven't used any teflon tape. Not wanting to do this again, I worked the friggin' thing out, wrapped the threads with teflon tape, and put everything back in.
Oil changed, I went upstairs (second floor), took shower, got dressed for work, and, went outside to start the car. Start, and oil pressure reads zero. As I sit there thinking "maybe the new unit is faulty", I hear gurgling sound. Shut the engine off, jump to see what's up, and, of course, couple of quarts of oil right there on the ground.
****!

So, a quick phone call to work to let them know I'll be late, and, back into work clothes. Air ducting off, alternator off, oil filter, oil pressure unit.
Teflon tape on, found the right hole, turn the engine over, to make sure there are no leaks, button everything up, and, GTFO.

I wish they'd make a teflon tape for morons like me.
$8.50 for 2 quarts of 10W-30 @ gas station around the corner. ****!

 

Lol I had a similar problem once. Built a new engine and found out that there was a little plug missing out of the head. You can barely see them but they're allen head plugs. Spit 2-3 quarts out real fast just like yours. ~70psi will empty your crank case pretty quick