I have a 305 TBI and im guessin it has the stock thermostat.. I wanna get something to make the car run a little cooler but im unsure of how low to go.. whats a good number to stop at?

 

try to find a 170*, if you cant get a 180*
although in the summer time you could still hit closed loop with a 160*

 

I got my 170* stat at the gm dealer for $7. No problems with closed loop and helps keep them temps down.

 

If you have read some of my post's you know my opinion on colder stats. Before you change make a record of your mileage. Then check it after you put in a cooler stat. I'll be willing to bet you lose anywhere from 2-3 MPG. There is also a good chance that if you need an emission test you will not pass. There is a common misconception that just because you hit CL that the engine is running efficiently. Closed loop occurs when the O2 sensor gets hot enough to send a voltage to the ECM(500-600 deg.). However fuel delivery(injector pulse width) is also controlled by the coolant temp sensor. If you do a lot of stop and go driving chances are that with even a 160 stat the temp will get to 200 degrees, but if you hit the highway it will cool down pretty fast and that is where the problem comes in. Fuel delivery will be based on a colder than normal temp and the ECM will try to compensate. The end result is a richer than needed mixture. Hence the loss in fuel economy. I would agree in Dallas in traffic you probably could get away with a 160 because the average temp of the engine will always be well above that, but overall the best driveability occurs with a 195.

 

ouch, i wouldnt want my car and 220-230 all the time like the factory had it. i have a carb so i just tune it to run the best it can run at about 170*

1992 Camaro RS LO3/700R4
Holley 600 Double Pumper, Weiand Stealth Intake Manifold, Accel Distributor and Coil, Hedman Headers and Modified Hedman Y-Pipe(Ported and 3" Pipe), Straight-Pipe Cat, Flowmaster 3" 2 Chamber Race Muffler, 160º thermostat, 3.73 Posi, Boxed LCAs, Kumho 255/50s, Polyurethane Transmission Mount, and B&M SuperCooler.

 

I have a 350 tpi with dual fans,anyway i run 220 on the highway, but when i am in stop and go traffic on a hot day the car will eventually climp up to around 230 something which is not burning up but is considered hot, but by no means overheating.

My car works the way gm wanted (factory : stock), a good performer with good mileage and good emissions. But their is some room for improvment. I am going with a 180 stat one of these days and a fan switch to make the passengers fan come one earlier. So i think that with those mods i should run closer to 195 to 200 then 220 to 225. Cooler engine more horsepower(better performer). I think a little cooler engine would not take that much from mileage or emissions, but the better performance and longer engine life would be worth it. And you can always get a chip to change everything for even better performance and better fuel mileage.

 

I would try for the 170 as well.

 

I'm running a 180 stat in my 305 with a flex fan, and I'm averaging 190* temps on the highway. it climbs to about 200 in traffic, but works well enough for me.

 

Consider the stock engine for this example.

If you want max MPG vs HP vs Low Emissions vs Longevity you will want your car to run at 194° at 1000 RPM. That is the factory spec and what it was designed for.

That was not a mistake by GM.

What WAS a mistake is thinking a 195° thermostat would produce these results. In MOST cases it won't.

The reason the thermostat temp issue is such a great debate is because we all live in different environments and drive under different conditions. Therefore it takes different temp stats for us to get the proper temp.

GM thought "one size fits all" ......... and it just doesn't.

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mine 305 TBI has the stock thermostat and mine stays at 150-160 going 65 on the highway.

 

I need to start posting this more. Iv'e found the most consistent temps with a modified 195 'stat. That and a good, clean cooling system. Take a Robertshaw-style thermostat (available at Autozone and others) and drill three 1/8" holes in the top of the housing as shown below. This type of thermostat is considered more reliable and accurate thatn the standard spring-type stats. The holes allow a small amount of coolant to circulate at all times, preventing the temperature spike before the thermostat opens. My car, a 305 TPI has been running this setup for 6 months now, and has never seen the far side of 220, even during a 1hour, 5mph crawl down the strip at the beach over Memorial Day Weekend

 

However.... again... it depends on where you are (environment).

I achieved the same results with 4 holes drilled, in a different location, on a 170° stat.

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