I'm still building my car, with a chevy v8 and moroso dry sump system. Since Moroso recommend that the tank is fitted "slightly higher" than the pump inlet I wondered if the oil from the tank could leak through the pump into the sump.

Obviously if enough oil gets into the sump from the much larger tank you could "hydraulic" the engine when starting it, right?

Moroso confirmed that indeed oil can leak back overnight, and this is why they recommend that the pump is primed before starting the engine each time!

On a road car this isn't practical, but there are many road cars with dry sump - porsche/corvette/etc - so do they have a solenoid-operated shutoff valve perhaps connected to the ignition circuit? or some other solution?

Or of course, is this theory and not practise - and very little oil leaks down through the pump..

From a practical point of view...on my drysumped cars of the past, I had a simple ball valve that I could close when needed. I also had a "Remove Before Flight" banner pinned to it because so often I find my head up my arse where I cannot see all that well!  My current two race cars are wet sumps so the problem is moot.

For a street dry sump, all I have is my 1948 Norton and it too has a shut off valve (with the same red flag precaution) as it will drain back 'overnight'.  The drain back problem was never too much bother on the bike, but once on a Pantara with a 24 qt. tank...I never took the chance and installed the ball valve from the 'get-go'!