I currently have a MotoRad Fail-Safe thermostat in my engine on the stand in 195*F rating, today I saw a post on a social media group I am on where the guy had his fail open with normal operating temps of 200 - 205 with his 180*F stat. I looked online and saw a bunch of people saying the same thing so I am going to pull it out and replace it before I get the engine installed and have that issue that seems so common.

Problem is though I have a GMB High Performance water pump which on Summit and Rockauto where I bought it state that its a High Flow/High Pressure pump that has a high performance impeller that increases pump pressure by up to 300% and has maximum sized and contoured passages to improve coolant velocity that increases flow from idle throughout the rpm range and claims it will reduce engine temp by 15 - 30 degrees. Yet unlike other high flow/high pressure water pumps no where does it state to use a high flow thermostat.

With that said the two thermostats I have on order currently to swap in is a OE Motorcraft RT1139 in 192*F which from my memory is the correct one for my truck and the other is a Stant Superstat 45359 in 195*F. Ive always ran the Superstat and never had an issue with them before but with my new engine having aluminum heads I got sold on the Fail-Safe thermostat to give it a try.

Does anyone see a issue with running the GMB 1251230P High Performance water pump in conjunction with a OE Motorcraft RT1139 or Stant Superstat 45359 thermostat that are both standard flow?

If it makes a difference the OE Copper radiator is being replaced with a Cold-Case F0T578A two core radiator to help improve cooling ability in conjunction with my 18" 7 blade flex fan. My main issue now is removal of the Fail-Safe thermostat and putting in something that wont cause a issue and I am concern cause other high flow/high pressure water pumps state you have to run a high flow thermostat with the exception of Flow-Kooler who uses GMB housings. I tried contacting GMB last year when I started buying parts but they never got back with me on if they recommend high flow thermostat or not.