ZERO oil pressure

[feliperv8]

Hello,
My name is Felipe, i have a RV8 with 50 hrs TT. Since a have installed a RAVEN inverted oil system i'm having problems with oil pressure, as soon as have it in the inverted position the oil pressure goes to ZERO psi and doesn't return to normal, i have shut down the engine immediately both times, and landed dead stick, not fun but landed safely. So i ask:
1) Any possible damage to the engine?
2) What is the beast course of action to inspect the engine for damage?
3) Any sugestion for trouble shooting the system?
Thanks alot,
Felipe.
Brazil.

[rocketbob]

1. yes.
2. remove the screen and check the filter.
3. The check ball is stuck, and its very sensitive to trash in the bore.