"Cool fuel temp".
Nope. The fuel temp is a function of tank
temp, engine temperature, and return flow. Moving more fuel thru the head by enlarging the orfice will only make it cooler for a SHORT TIME. As you move more fuel thru the head, it will transfer more heat from the head back into the fuel tanks
, which will obviously increase the tank
and then the inlet fuel temperature.
Stock, a Series 60 will RETURN 90 gallons/hour of fuel during "cruise" to the tanks
. If you enlarge the orfice, it will return over 120 gallons/hr, and as much as 150 gallons/hr.
Returning more HOT fuel (much hotter than when it left the fuel pump) to the tanks
, CANNOT reduce fuel temperatures, except temporarily.
I could go thru the math on how long precisely, but w/o knowing the new orfice size, it would not be worthwhile.