Water inlet

I bought a 73 mustang 16 that had been taken apart for a restore and when I bought it, it was a box of parts. After restoring it over the winter I finally took it out today for a leak test. I initially had an overheating problem that I resolved after pulling the hose past the pre water pump and sucking on it until I got water.

After that, the hose flowed water and the temps went down. Pre pump has new impeller and I am certain I have the in and out correct. As far as the rest of the cooling I assembled it based on pictures so something might not be correct but I'm pretty sure it is.

My question is this, is the inlet supposed to have a check valve to keeps it primed? It seemed like it struggled to prime but was good after it did.