Just some guy
Join Date: Jun 2001
Location: SC foothills, USA
The belt driven fan is a puller. You will mount your fan in front so it will be a "pusher". Basically it will act as a booster to the original fan. IMHO, if you need the extra help cooling the engine at idle on hot days you have cooling issues that need to be looked into. Not to say the extra won't help, it can, I've done it as a temporary band-aid fix myself.
Right now both my F100 and Bronco have added pusher fans. In both cases I use the pusher fans for extra airflow when running the AC during extended idle times. Neither truck runs hot without the fans but both are R134A AC conversions. When the pusher fans are activated I see a redution of about 30 psi in compressor head pressure. This basically means colder air out the vents versus not having the fans. You will see some of the same effect on the radiator too.
.... it wouldn't be the first time reality took theory and conjecture out behind the woodshed and gave them a good thrashing.