if its heating up that fast then the new stat is bad. Make certain you idle it with the cap off until it warms up all the way then you will see the water flowing across the top of the radiator and as the stat opens it will burp the air up and out. Then you can add more water until topped off and then place the cap on. The fan will only affect cooling under maybe 30mph, beyond that speed it should stay cool on its own from airflow. The water pump impellers on some pumps are pressed on and can slip internally also impeller corrosion will cause them to cavitate and have poor flow. You can test the coolant to see if hot exhaust gas from a bad head gasket or head is leaking into the coolant which will boil the coolant fast. Pull the plugs and check the electrodes they will show if coolant fouled also make certain that someone didn't put the 2 steps hotter heat range plugs in that the 70,s model 360s used. The later 80's 90's used a colder plug and a leaner mixture for emissions reasons the engine will run cooler and less detonation prone. Make certain the catalytic converter isn't blocked and that the exhaust heat riser on the passenger side manifold isn't stuck shut forcing hot exhaust to cross over through the intake 100% of the time. I wired mine open. Next check that the thermal actuators on the air cleaner snorkel are opening for full cold air and not grabbing preheated air off the passenger side manifold.
06-Corvette z51-6spd,b&b,K&N low miles.
77-Corvette Stingray 496 BBC/TH400 built 667hp+
00 WJ 4x4, 4.7 stroker, turbocharged,..lots more..
01 WJ 4x2 4.7v8 Limited (needs valve job)
90 Grand Wagoneer 401 Edelbrock Heads, Lunati .510/.527 FT Cam, Edelbrock RPM Air Gap, Holley HP 750, Thorley Headers, HEI, Electric Fan w Digital controller,4" lift 31x10.50 Goodyear Duratrac's on Pro-Comp Wheels,new interior, seats,seals,Alpine and JL full system, Remote HEI, Clifford 2 way with remote start,windows,tailgate.
96 Cherokee Country 4dr/2x2 White/Tan 3" Lift Sahara 18" Wheels 32.5"'s 99up head and intake- for sale soon!