350 SB thermostat-- what temp?

[Driftwood]

I'm going to replace the thermostat on my 69 350/350 SB. What temperature do people recommend?

Thanks,
Andy

 

[Stallion]

A lot of people go with 160, but a safe bet would be 180. I think the temps you want also depend on different aspects. I'm sure somebody else will chime in, too.

TR

 

[Ganey]

180

http://performanceunlimited.com/illustrations/thermostats.html

 

[Driftwood]

I don't race my car-- I just cruise around if that is a factor. I'm in Chicago area if ambient temperature is a consideration. Why is 180 safer than 160? Is the fear that too low of a temp will damage the engine?

 

[Stallion]

Well, performance wise I think a 160 is a little less than something like 180 or 190.

 

[Driftwood]

OK-- than 180 it is. Thanks.

 

[Bob Chadwick]

It's possible to run the car too cold as well as too hot. The later Sharks, with their smog equipement, are more efficient at a hotter temperature. I'm not sure on the earlier cars.

 

[MaineShark]

Stock was 195, for smog reasons (higher temp = lower smog).

180 is better for performance.

160 is too cold. You'll increase wear on the cylinder walls, leading to decreased engine life. Better power, yes, but not for long, as you'll lose compression as the walls wear. Fine for a race car that gets rebuilt all the time, but for a street-driven car, you'll see a small increase in performance for a time, followed by a gradual reduction in performance, ending in an engine rebuild.

Of course, if your cooling system isn't capable of cooling it down to the termostat temp, it won't matter what you do to the thermostat. In other words, if the best your radiator/fan system can do is 200, you could put in a 160 thermostat, and not see any change (except in warm-up time).

Joe

 

[Driftwood]

Thanks for the info. Can you tell me in a few words why a cooler engine has better performance? Is it because the air expands less coming thru the carb into the cylinders? Just curious.

 

[MaineShark]

I'm pretty sure that the manifold/carb temp is part of it, as well as the combustion characteristics. I mean, the change from 180 to 195 made a significant reduction in smog (and modern cars run even hotter, in many cases), so I'm sure that the change in the combustion chemistry is fairly equal in size, when dropping 20 degrees below the 180 situation.

I believe that the cooler temp also reduces the tendency to knock, allowing more ignition advance (similar to the way that EGR cools the charge, allowing greater ignition advance).

I'm sure someone here knows the details.

Joe

 

[biltogo]

Stock was 195, for smog reasons (higher temp = lower smog).

180 is better for performance.

160 is too cold. You'll increase wear on the cylinder walls, leading to decreased engine life. Better power, yes, but not for long, as you'll lose compression as the walls wear. Fine for a race car that gets rebuilt all the time, but for a street-driven car, you'll see a small increase in performance for a time, followed by a gradual reduction in performance, ending in an engine rebuild.

Of course, if your cooling system isn't capable of cooling it down to the termostat temp, it won't matter what you do to the thermostat. In other words, if the best your radiator/fan system can do is 200, you could put in a 160 thermostat, and not see any change (except in warm-up time).

Joe

I agree.

I've read a number of "studies", and they mostly say the best compromise of engine life and efficiency is block/head temps in the 180-200 range.

I also have a C4. I don't agree with those Hypertech chips that improve performance by advancing the timing and necessitating a 160 T-stat. It's a marginal gain usefull only when you stomp it,

Getting the coolest intake air possible, is a better time and dollar investment than running the block too cool with overly advanced timing.