Up until last month I had a mechanical temp gauge in my Monte because
my dash gauge is not working. When I installed my shorty headers in
May, I forgot I had to remove the mechanical sender before I was able
to remove the old headers (very inconvenient). Rather than make a mess
and pour coolant all over one of my car club member's shop floor, I
just cut the sender's "tube." Today I replaced the mechanical sender
with an OEM replacement electric sender and installed a new temp
gauge. I am now having a problem with the car overheating. Sitting in
my driveway idling, my car wouldn't go over 200 degree's, but when I'm
out driving it will slowly creep up to 240 degrees and hold there.
What could the reason for the engine getting that hot?

My electric fans are both working properly, I've got an aluminum
Edelbrock Victor series water pump, the belt is there, I have an
aluminum radiator and last year (when I did the cam swap in April) I
installed a 160 degree thermostat. I have a termo-cap radiator cap
that reads what the temp is inside the radiator and it gets to almost
the 200 degree mark.

Dustin