Ive found this out the hard way. After replacing EVERYTHING, I put the stock fan back on and problem was fixed.

 

I disagree with this, I have always run 160 thermostats and in traffic car runs around 180-185

 

The point is depending on how effiecent the cooling system is will determine how well it will cool. If you have a cooling system that doesnt not get heat soaked and can dissipate the heat fast enough you could run with out a thermostat. I've used 160's also but i also had a BE COOL 3 core aluminum radiator, a Mark VII fan with a HI-flow FMS water pump. i could sit in traffic with the fan on the low speed and it would never go above 180.

 

i just ordered a ford taurus fan and an oversized 3 core racing radiator. lets hope between those 2 things it stops the problem!! thanks for all your input everyone much appreciated!

 

The three core alone should take care of the problem. The fan was overkill...But, I guess if you want to run in the AZ desert, you still can.

 

at that point you could have run a 100 degree thermostat and your car would have run 180-185.

I like at least a 180 in an EFI street car. BUT>>

When the motor gets hot, its hot. Once the thermostat is open, its open and only serves the purpose of being a coolant flow RESTRICTER for an inadequate cooling system. If your radiator/fan did their job correctly one wouldn't need to slow down the flow of water through it in order for it to be cooled in the radiator.

Everyone who has dropped mad cash on a high flow pump needs to remember that they only need enough pump to flow the coolant through an open thermostat hole.