After reading a number of posts on the cooling board I am beginning to wonder if cooler isn't better. I have had this engine in for about 3 or 4 months now, and I am running without a t-stat for the summer. My temp stays pretty steady at 150 degrees during normal driving. I was running a 160 t-stat with my 305 in the spring and a 180 in the winter. The car usually runs dead on the temperature rating of the T-stat.

When I first purchased the car the temperature ran up to about 220-225, and I felt very uncomfortable with it in this temperature range. I purchased a stewart stage II pump as well as an aluminum radiator from Griffin. This brought my operation temperature down to 195 with the stock 195 t-stat in there.

Now from the reading of various posts most are saying that the normal operation temperature should be somewhat close to 200 degrees and that running an engine cooler than that causes wear and decreases gas milage. I think I tossed the 195 t-stat, but I should have the 180 somewhere in the garage. Let me know your suggestions as to which one to run and your views about various operation temperatures. Thanks

 

From what i understand the engine runs better (ie more power) when its cooler, but the problem you run into is that the ECU is only going into closed loop operation at about 195-200 so you will loose some power and a fair amount of gas mileage running cooler than that. I would suggest if you know some one or have the equipment that you look into a custom prom and see what you can do about the closed loop operation temp. Really though if you ran about a 170-the factory 195 t-stat you should do pretty well. Wish my car ran that cool.

 

Not running the computer...

 

Ahh well still the 200* thing is for the cars that run an ecu (fuel injected only i think) really. Now i do imagine there is an operating range that is best for your setup but it probably isn't as high as the stock engines are. I would say if the car runs right and feels like it gets enough power then you are running about were you need to be, but i wouldn't think anything below 160* would be a good idea.

 

Just for the record, closed loop occurs well before the 195 mark. Closed loop actually begins when the O2 sensor gets around 500-600 degrees. That is the point at which it starts to generate a signal back to the ECM to control fuel delivery. In a typical TG it can happen when the temp guage just starts to come off the stop. A simple way to check it is start the car cold, you will see the higher rpm when it is on cold program. As it begins to look for O2 sensor input you will momentarily hear the engine drop rpm then raise it again. When this cycling stops and the engine rpm's stabilize that is closed loop. While coolant temp does play a role it is the actual operation of feedback from the O2 that determines when it is achieved. With a non-ECM controlled carbed engine any temp past the point where hesitation and rough idleing go away is an OK range to run since fuel delivery is independent of coolant temp or exhaust gas oxygen content. Proper fuel atomization is more dependent on intake manifold temp than anything else. You could probably run anywhere from a 160 on up and you will probably not really notice a difference. With feedback carb or EFI models the 195 target area is chosen because it provides the best operating temp to be able to control emissions and the ECM programming is designed to provide the ideal f/a ratio at that temp.

 

Thanks for clearing things up for me. I'll throw my thermostat back in there and get the car back up to 160

 

Learn something new every day.