recently in my 455, I had a 180 therm. It would run at 190 all the time but as soon as you stopped moving for a little bit it went to 200 to 210. So i went out and bought a 160 heavy duty therm. from NAPA. i installed it and now it runs at about 172 to 175 all the time, and it take a good long time to get up to 200 degrees. the question i have is what is too cold of a engine temp that make the fuel not atomize right and wash out the cylinders. I know if you run too cold, the fuel goes into the oil. am i ok with anything over 170? thanks
I am running at 175 at idle and 160 when on the road. I am kind of curious myself, as I am hoping I'm not running too cool?? I have a 180 thermostat and a 4core radiator. Runs very cool. BTW, your MO is in the mail!
It is my personal belief that 170* is a little too cool. I guess it depends on a lot of other variables, also. How rich is the carb? What is the oil temp? Ect. I think I heard once that GM determined that engines work "best" in 195*-205* range, but that might have been refering to oil temps...not coolant temps. I wouldn't be scared until water temps went OVER 220*. Jeff
I agree, 170*F might be too cool, especially if you run synthetic oil. The oil needs to warm up to get rid of moisture, and won't do it at 170*F with synthetic. I'm guilty of this too, but my engine will see 190*F on the highway, so I'm not too worried. If you have a 15 psi coolant system (very common for 455 cars) your boil over temp is all the way up there at 247*F. Don't forget that you'll see a temp "spike" when you turn the car off, because the coolant needs to flow past the sensor for it to work correctly. I see 210*F on a very hot (95*F ambient temp and very humid) day around here in summer at around 85mph. I've never boiled over with the system I have now: modine 4 row radiator, semi-enclosed cooling system with factory overflow, 50/50 coolant/water mix and 160* t-stat, viscous fan clutch, 7 blade factory steel fan, factory fan shroud. I've never seen over 220*F even in long term traffic on a hot day with this setup. From discussions on this topic with Jim W. and others, I beleive that it was general agreement to run at around 190*F on a street car with the 455, for maximum efficiency and performance. The 160* t stat is more for racing purposes than to solve any coolant temp problems.
Well I think the whole gist of it was that the low temp t-stat wasn't doing you any favors. Do you use synthetic oil, Adam?
Nope...I use the real stuff:grin: And now I've developed a miss...time to start a new thread about that oneo No:
I had to with four-core, otherwise engine would never warm up to a decent temp, especially in the winter. My defrost was cold !
My GS runs at 170* most of the time. Oil temps are much higher than coolant temperatures, certainly high enough to burn off any water in the system unless the car is used for short trips consistently. I'm not worried and I use synthetic oil. Been doing it this way for 4 years, and the engine is nice and quiet and the oil looks great.
You are correct, Larry, oil temp is not coolant temp. I am not suggesting they are. Lacking an oil temp gauge, all I can do is make an eductaed guess about oil temp vs. water temp and what temp the oil may see at any given coolant. naturally water in the oil would have to get to 212*F to vaporize.
I think all I was trying to say about temps is that you can over-cool the engine leading to condensation in the oil, cyl. fuel wash (especially with rich settings) causing excess wear due to lack of lubrication, and even loss of power from rings not sealing fully. Pistons are designed to expand a certain way with heat, especially forged pistons. I think I'm saying there must be a balance, between too hot and too cold. The general rule is something like 190*-210* oil temperature. Now this is most definetely NOT what must be maintained ALL of the time. That oil temp is the best for power, and engine longevity, IMO. But coolant temps generally closely follow oil temps, although it usually takes oil a little longer to come up, and then usually passes coolant temps. Whether or not oil temps are much higher than coolant temps remains a doubt in my mind. I'm sure it depends on many different variables. Too many to really list, but some are internal frictions, clearances, coolant capacities, ect.
The only time I ever saw water in the oil(other than a head gasket problem) was when a friend of mine had some bodywork done. The shop had the car for two weeks in the winter, and everyday they would fire it up to move it around. When he went to pick up the car, he checked the oil and saw some white froth on the top of the dipstick, and on the underside of the oil fill cap. He drove the car 2 hours back to his home, running at 175* the whole way. Parked the car and checked the oil the next day, it was all gone. As far as forged pistons are concerned, I agree, they are fitted with looser clearances because they expand more as they heat up. If they don't, you hear the dreaded "piston slap" But aren't the pistons heated more from the heat of combustion in the chamber? Would that vary with 20-30* difference in coolant temps? I have forged pistons, and like I said, my engine is quiet, even when it is cold. Chris, just curious, why would synthetic oil be any different than dino oil when it comes to accumulating water or getting rid of it? Synthetic oil is oil that has been manufactured with the best polymers to maximize certain properties. It's still oil. By law, all motor oils must be compatible and be able to be mixed.
Well, I don't see how the temp difference would violate any law, since you can ideed mix them and it's compatible, but I've always been told, from folks here to other old car guys to pros in my family (not automotive mechaniocs, however, aircraft mechanics) that because of the different properties, the synthetic 'holds onto' mositure at a higher temp, sort of the same reason it resists thermal breakdown, if I remember the reason?? I'll have to ask my uncle Will if I recall that correctly. Of course, what the oil company CLAIMS and what is really the case could be two different things...
