Thermostat

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Well i have an 85 olds cutlass ciera with a 3.8L 4 speed auto with OD. The engine was just recently rebuilt. Im trying to crack as much performance out of the engine as i can. My first question was i have a 195F thermostat in right now, the temp is fine when driving. But on a hot day 90F or so at idle the temp gauge starts to go up. Well we all know a colder engine performs better than a hot engine. I wanna switch the thermostat to a lower one for the summer. I have a couple of options, at first i wanted 160F from Hypertech, than i saw Mr. Gasket makes a 160 thermostat for my car as well and its suppose to be very accurate no matter what the pressure (rpm). Has anybody has experience with putting lower temp thermostats in? Will a 160 be 2 low that it will basically stay open all the time and the coolant wont have enough time in the engine to absorb the heat and the coolant wont be in there long enough to get cooled down that the temp wont show any different. If thats the case Mr. Gasket makes a 180 as well would that be better?

posted by  speedy266

I think your trying to takle this from the wrong end of the problem.
If the thermostat works fine in the winter then surely in the summer it is fully open already and your not able to disipate the extra heat thats why the temp is rising.

If you think about it a bit like this, say you have a hot jug of water, put it outside in the winter and it will be cold in 20 mins because the diffrence in temperature means that it cools quickly.

take the same hot jusg and put it in the arizona desert in the middle of summer and it wil cool a little bit but as it gets closer to the atmospheric temp then it cools more slowly.

So rather than changing your thermostat then you might want to look at other ways of cooling oil cooler for example, electric fan, just flush your coolant system helps. The fan draws alot of power from the engine and isnt that efficent compared to an electric fan.

In the summer another thing you can do is change the concentration of the antifreeze as water can absorb more energy (4.18kj/kg) than glycol (about 2)

but remeber to put it back in the winter or your system might freeze and that isnt good!

If you do reduce your engine temp then the eficenty is likely to go down the manufacuters in the main have got the balence struck between engine wear, perfomance and eficentcy.

If you do add an electric fan or oil cooler you will need to inser an aditioonal thermostat to regulate cooling.

posted by  cinqyg

You said you had it rebuilt, how much were the cylinders bored?

posted by  DodgeRida67

Thank god he's here

posted by  cinqyg

Is that sarcasm?

posted by  DodgeRida67

it was a stock rebuild they were bored to give them a new finished surface.

So changing to a lower thermostat wont help the engine run cooler even by 1 degree?

posted by  speedy266

by moving the temp it will make the car take longer to warm up, and in average conditons then it will bring the temp down, but as your taking about when its really hot and therfore we can sume that the stat is already open full as it raises above normal temp then its basically the diffrence between a fully open thermostat and a fully open thermostat?

posted by  cinqyg

fully open thermostat/fully open thermostat = 1F :laughing:

posted by  speedy266

Well staying on the topic of cooling, i pulled my underhood cover to dampen sound, but it also holds in alot of heat. After i did that the coolant temp gauge always runs one notce lower than it use to. I have coolant lines going to my throttle body, ive read about a TB coolant by pass, as it reduces the temp of the TB and the intake manifold, in turn having cooler air. Anybody done this?

posted by  speedy266

The heat helps vaporise the the fuel, you couls but it would reduce the fuel efficentcy, and have other effects probibly.

I know this soulds dumb, but why are you spending all this time playing with that engine and its cooling for extra power. If its power your after then why not just swap the engine?

I can understand wanting to imporve the cooling if its running hot or you want to tow, but for power purposes byt the time you have done all this you could have droped another engine in.

posted by  cinqyg

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