Originally Posted by Steve Hellums

I just left the OEM on. If I recall right the OEM pump puts out around 4 gpm and the Johnson is somewhere around 7 gpm. Sometimes more is'nt better, but I really don't know in this case. I was having trouble with my old Stang overheating at highway speeds after putting 3:55's in the rear, at 60 mph it was taching around 2,900. I first thought it was sucking the radiator hose shut, so reinforced hose's well that wasn't it. I replaced the thermostat with a new Auto-Lite, flushed the system and a new radiator cap. I had thought all along it was just pumping the coolant through the radiator to fast for it to cool, I had guy's tell me no way & other's say that's what it was. I put 3:25's in it last fall, now I'm taching 2,600 at 60 mph and she stay's around 180* now. In this case the coolant I believe was being pumped too fast, I wanted to change out the water pump pulley with a bigger one, but it was already close to the crank pulley.