Dam I forgot. aigomorla
I noted Skinee said he didn't have a manometer. So he couldn't check resistance to flow. Long ago if we were in a position were were a mano not to be had . A simple Water pressure and Vacuum guage works nicely. Place the pressure guage at outlet of pump,. The vaccum gauge at the return of the pump. Run a length of tubing to inlet outlet of said pump make it a 1/1/2 footer. Than run pump should be pressure at outlet and negitive pressure at the inlet.
Than cut tubing don't shorten . Than attach to rad retake the messurements . Than use the math. By cutting a 1 foot tubing and attaching at iN /OUT pump. Retake measure meant that gives ya the pressure drop threw for 1" of tubing. Now use formula that will give pressure drop or resistance to flow. Beings how he is using flow meter to hold pressure 1 1/2 gpm You should get very close to manometer numbers. I admitt I like our DP-330 alot better than that method. But if in a pinch . Captain cavey did ok got us here ant way.