oke you are using a water meter to check your oil
Yes it works a giant of
Meanly your are missing a liquid demping in the meter.
The pulsing is clear working from the pump ( thats good ) at temp. fast lowering is a sign that the oil is fast leaking to any ponit as by design required ( thats good )
If you do not see the pulsing you are not pumping or low flow.
if your oil is from the wrong grade or your engine is overheating you will see the puls very narrow ( thats bad )
i hoop that i help
p.s. by any rebuild or update put a double cam on the shaft. that means double oil flow.
Greetings from Greece