the thermo is by passed at the intake and pump and will flow x amount of water with it closed

that is so it does not cavitate while cold,the water is moveing

you can run into probs with the intake blocked, when cold and at high rpms

how many vanes on the pump and a/c or non a/c pullys plays a part also

8 vanes for the larger non a/c pully
6 vanes for the smaller a/c pully

a/c pully on a 8 vane pump can cause it to suck a hose flat or cavitate at high rpms

they are matched to pully speed and vanes to move the same x amount of water at idle

large pully turns slower and has 8 vanes

smaller pull turns faster with 6 vanes

a thermo does help direct water to the smaller head passages and helps direct flow

the intake by pass hose is often thought of as a way of warming the engine up to temp faster...which it does...but its to let water flow with out it cavitating while the thremo is closed..or like said when cold and being reved up

I have found pieces of the spring "coil" in as far as the t-cover or wraped around the impeller also

also have changed some alum t-covers from cavitation eating the alum away enuff to leak,and seen them leak water into crank case

cavitation damage looks like casting flaws that are bubble shaped pocket/holes that have been eat into the alum

look at some off a mercruzer off shore boat engines that turn 7000+ rpms for sustained lenghts of time

more to it than pumping water with restrictions in the system

got spring?