There is no way a GOOD 160 thermostat will allow an engine to run cooler than 160. If your gauge is saying 150, you have a gauge problem.
I suggest you take some infrared thermometer readings and find out if your gauge is reading correctly. The fluctuations could be a sending unit or gauge problem.
A radiator should drop 25* inlet to outlet under any conditions.
Most people don't realize that with a big (copper or aluminum) radiator you need to overdrive the water pump and/or use a high flow water pump. The water flow must be fast enough through the tubes to create turbulence and break the laminar flow of the coolant or the radiator will NOT cool like it is suppose to. This is why so many hot rodders install bigger radiators and still have cooling difficulties.
You definitely need a stock type shroud under any circumstances.
Last edited by ScoTFrenzel; 07-18-2008 at 09:21 PM.