Are you sure there is no air trapped in the system somewhere?
I used the GM big block serpentine kit, it included the water pump, pulleys, belt, etc. So I am hoping that they have that all worked out.One more thing to check. On a system where you have changed pulleys, you might be turning your water pump at the wrong speed. I know a guy who just spent north of $7K trying to solve an overheating problem on a Mercury big block. He had the wrong diameter water pump pulley, and it was underdriving the water pump speed wise. He found out that the correct ratio was either at or close to 1.3 rotations relative to the crank pulley, and that was what water pumps were set up to do. With serpentine systems made to adapt to many engines, you might not have the right ratio. Check this thread:
Is the fan a reverse rotation piece? I run an 18" Derale Reverse Rotation mechanical fan on my 383 with a GM serpentine setup--runs about 160° on 90° days. Didn't work worth a damn with a regular rotation fana derale steel mechanical fan
Swapped from a 350 to 454, but now I'm battling overheating. On the big block I am running the Chevy serpentine kit with reverse long water pump. The pump is brand new, so is the engine. It's a GM crate 454.
I have a 180 degree thermostat and an aluminum radiator with a core that's approximately 2" thick by 20" wide. Running two 10" 1000 cfm fans that are pulling the right direction. I have a condenser and trans cooler in front of the radiator but ac is not plumbed up yet.
Car will overheat on a 70 degree day quickly. I watch the Temps Creep past 225 and won't stop. The only way to keep it cool is to jump on the hiway. But at 80mph it still climbs to 195 degrees, where it finally stabilizes.
Thoughts? At first I thought the fans were insufficient, but then at 80mph I would expect much better results even with no fan. I also don't have the inner fenders installed right now, but I wouldn't expect a huge difference from that.