Hiflow Waterpumps

I've used a couple of flow Kooler ones and so far so good. I made the mistake of replacing the original 8 vane wp on my 78 318 with a 6 vane version and right away I noticed that my engine was running noticeably hotter as soon as I bolted the 6 vane version on and filled it up. I then re replaced it with a flowkooler and back where I was before the 8 vane started leaking.