Originally Posted by Blown496
Is the temp sensor in the head or intake? Fan sensor in head or intake? I have my fan sensor in the aluminum head at 195 and the temp sensor in the intake. Blown 496 with Griffin 1 1/2 tube radiator. One pusher fan in front and a fixed performance fan on engine. Runs 185 in traffic and 180 at speed. fan never comes on until I idle a lot or after shut off. I run a high flow tstat with relief hole and high flow Eddy pump. Timing is 16 at 1000 and 32 total. If it heats at speed it is air flow and/or timing. You said plugs don't look lean. Is the shroud flush against the radiator?
After reading through all the replies I was wondering when someone was going to ask where the fan temp sensor and engine gauge sensors were!
There are huge differences between a sensor that picks up in the cooling fins of the radiator, and also between aluminum heads and a cast iron block, or intake sensor.
The best place to install the fan sensor is the aluminum heads since they heat up way faster than anything else, and the best place to monitor engine temp is in the intake, as that's the return temp on a Chevy engine.