Question Ideal fan & radiator placement

Jul 12, 2019
I recently replaced my front intake fans with a pair of corsair ll series 140 and now I'm planning on replacing my rear outtake with a corsair ll 120 to match (currently an sp120). I'm also thinking about setting up either a corsair hydro series H80i or a corsair hydro series H55 for my cpu.
I was wondering if its better to have the radiator for the liquid cooler on the rear or the top? and is it better to have an outtake fan on the rear or the top?
I've heard the having the radiator close to the gpu can cause it to heat up from the exhuast heat, would it make much difference or even affect the radiators performance?
My case is a corsair carbide-spec 03, currently with dual 140's in the front, single 120 in the rear and stock cpu cooler. And in case its useful my mobo only supports three case fans and two cpu fans
For best airflow, front intake and rear/top exhaust still works best for cooling. Intake and exhaust should be about equal with slight advantage if there's a bit more of intake air.
Don't know what CPU or cooler you have for it but single 120mm AiO coolers are at best just as efficient as good tower air coolers of same size. If you do put one of those it doesn't matter if it's at back or top but should be set as exhaust.
I don't see how you could possibly place radiator like that so close to GPU that it would matter but in any case , radiator will be much cooler than GPU anyway. They rarely go over 40c even when CPU is overheating.
Mobo may be supporting only 3 case fan headers but that doesn't mean you can't use splitters for 2 or even more fans on one header depending on power they need. One restriction is that two fans going on same header be same for proper speed control.