what temperature is it that you would decide it's time to pull over...........those of you with manual fan switches; what degree do you realize it's time to turn them on............and lastly, what is the optimal operating temperature for a l98 350?

 

anywhere between 240 and redline.

 

I would agree with that. Also, if you have had the car for any period of time you should know when something looks unusual with the temp guage. Asking what the ideal temp for these cars is like posting a religious or political question, but the experts I have spoken with from the big 3 all say the same thing. 195 degrees. At this temperature all engine parameters are optimized for fuel economy and emission compliance. The ECM programming looks for a target operating range in that area. Every time I ran colder stats my gas mileage went down. And it's not because I am cheap, to me mileage=efficiency.

 

Religious or not you are absolutely correct. At 1000 RPM the calibrated temp by GM is 90°C which is 194°F. This is the best temp for economy vs emissions vs power. This temp may be varied to effect any one of these 3 areas.

The stock 195° is perfect in theory if it operated as designed on paper. But in the real world they forgot the 10 to 30° margin of error on the guages, margin of error on the coolant temp sensor, the 20° range it takes the stat to fully open and the +/- 3° margin of error on the stat temperature rating itself. Coupled with a stock fan that doesn't kick in until 234° you have a recipe for disaster in some climates and conditions.

 

All good points Mike and I agree with each one. However that is why it is critical to run tests on guage accuracy and to know what is actually going on. Such is my case for preventative maintenance. One thing I found very interesting about stats. Case #1, my wife's 98 blazer. Got to 50K and decided to flush and service the cooling system. Put in Stant stat, stock 195 replacement. During normal running the guage ALWAYS rested on the first line on the temp guage. Replacement stat read about 2 needlewidths higher than stock. Got another one, ran even a little higher. Went to dealer got a stat from them and the guage sits right were it did when it was new. Case #2, 89 IROC 5.7, got mine in 91 with 19K. Girl I bought it from complained about chronic overheating problems. I found a burnt connector at primary fan relay plug. Fixed that but it seemed to run hotter than other TG's I worked on. According to her records the stat was replaced and the temp sender also. Put in an OE stat and it ran cooler but still not right. Replaced the sender with OE and it runs right on the line between cold and 220. Smack dab on it. I would suggest that although Stant make the OE stats for GM, the ones that actually go to GM are probably better quality controlled. My daughters Cavalier ditto, it runs right on the line at 195 in the middle of the guage. Put in a different stat, it is up or down. I used a Weston instruments analog guage with a temp probe and with the cap off the rad on the rock the stat opened at 197 degrees. Not too shabby. My point is that with stock parts and everything in good condition the guages are pretty accurate. Let's face it these cars are getting old and who knows what has been done to some of them over the years. By the way on dual fan setups primary fan comes on at about 220-225 degrees, aux at 238.

 

My stock 350 tpi dual fan, i run 220all day long according to the stock guage. Sitting at lights in traffic when the outside temp is hot, is when my car starts moving up in temp and the fan(s) start coming on. Lately in Md we have had some hooootttttt temps around 100, and i was sitting at this one light for minutes and my car temp went up to like 230 - 235 and the fan(s) kept it there and then started to come down a bit.

so i guess i would pull over when i see my temp rising past 240, but that should never happen unless i have a failure somewhere.

 

at 240 i would pull over. i usually am at 160* 90% of the time but with 100 degree temps and 100 percent humidity it gets up to 220. i manualy turn my fan on at 165*