What degree theremostat should I get for a 425hp 454 with stock iron heads?

The answer you'll get will vary. I would say a 180*. Thats what most that i've seen use.

i run a 160 in my 350 with stock heads about 340hp. i like it, doesnt get above 160-170 in traffic with a stock 7 blade clutch fan.

aaron

I see you live in Florida. Since you live in a warm climate, it
would be better to run a 160. Ask for a superstat. This one has
a larger area of flow. Before you put it in the car, drill a 1/8 th
hole on the flat portion (around the edge) of the stat. This
will help bleed off any trapped air you may still have in the
system.

This should work like a charm. :)

I run a 180.

I prefer the 180º also. The higher temp increases the amount of condensation in the crankcase that gets evaporated and it also helps to reduce the amount of condensation that forms in the first place. While a 160º stat might provide a noticeable power improvement in modified late model computer contolled engines, I wouldn't expect any improvement in a non-computer engine.

I run a 180 in the 70 and the 67.

I have always heard that you should run a stat 20 degrees cooler then what you intend to run. Whether thats true or no, I don't know. Just one of those automotive 'legends'. I run a 160*, and never goes above 180*, and usually stays in the area of 170*.

Chris

I would run a 180*, your engine needs to run at at least 180* to burn the toxins & contaminates out of the oil...... At least, that it what I was always taught..

. While a 160º stat might provide a noticeable power improvement in modified late model computer contolled engines, I wouldn't expect any improvement in a non-computer engine.

Just from what I have found in playing with stats in both -

In either case the added performance comes from retuning, not just from the stat change. Cooler temps, more agressive timing without getting into detonation.

Stats dont change performance but allow you to change tuning perameters to add performance. Doesnt matter if its computer or non-computer controlled. In one you do it, the other you tell the PCM to do it (timing tables, on / off temps of fans, etc).

I figure that timing is timing and cooling is cooling and detonation is detonation no matter computer or non-computer controlled and in both cases there is the potential for performance as well as potential for wasted time, depending on the specific build / car.

I run a 180 in my 396/425 horse with no problems. Everyone is right about the condensation, you gotta heat the motor up to burn it off. If your strictly racing I would run the 160

A closed loop control system (computer controlled) will waste gas big time if it is run below the temp expected by the controller. It knows the engine is cold and continues to run rich. Not good.

It really not a good plan on a carb'd engine either for the reasons cited.

The tstat temp is the opening temp. You'll probably experience a 10 degree increase in op temp over the spec on the tstat- assuming your cooling capacity is up to snuff.