H150i change fans to 140mm

Hello guys i have one h150i pro hydro cooling and a case of coolermaster h500p mesh.I have my radiator put on the front and i was wondering if i could gain lower temps from changing the 120mm fans to 140mm fans(for those that will say cannot mount them or how....my case has a variety of holes to screw your components).I asking cause i don't know if the fan is not fit exactly on the radiator how much % of its efficiency on cfm will lose and how much more dropping on temp on my coolant will see.

It will loose quite a bit of efficiency. Nearly all 140mm fans (even those designed for radiators) have a pretty wide exhaust flow. You will be blowing most of your air out the sides. If you feel like you are not getting enough air into the case (or through the radiator for cooling), you would be better off adding additional 120mm fans on the opposite side of the radiator for push-pull set up. This is usually a small improvement in terms of CPU cooling, but may be more beneficial if you have hardware directly on the other side that may benefit from more airflow, like m.2 drives or possible the chipset.