I have an 87 TA 305 tpi. When I got the car I had a problem with it getting to hot in town. I put in a 160* thermostat and a manual fan switch. Now it runs on 140* on the highway and about 195* in town, It's never reached the 220 mark since I put in the thermo. The manual fan switch is of no use because it runs cold enough that I don't need to switch it on. Is this to cold? I don't think it is, I can tell a considerable difference in power when it is running cold. Just wondered how cold is too cold?


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1987 WS6 Trans Am
305 tpi, 3.23 gears, 160* stat, 1 1/2" drop springs, flowmaster catback, cam, strut, shock, bushing, balljoint upgrades, and don't forget the system.

 

I've read in alot of articles that most 3rd gens need to be atleast be somewhere around 170-180 for the sensors and(ecm) to function
and I didnt know until a few day ago, a gm tech (retired}, told me that these cars were
intended to run hot right around 210 for emmissions

 

Most will say 140* is too cold, that is probably killing your mpg as well.

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'86 IROC
T-TOPS, TINTED WINDOWS, BRAKE LIGHT BLACKOUTS
GM GOODWRENCH 350
EDELBROCK TES HEADERS
3" Hooker CatBack w/Aero Chamber muffler
EDELBROCK 600CFM CARB.
KN AIRFILTER
ACCEL HEI DISTRIBUTOR
160* Stat
3:73 Posi
Rebuilt 700R4
B&M Megashifter, 5" Autometer Tach w/shift lite

 

anything under 160 is too cold. 160 is even a bit cold, but with a 160 stat usually they won't run that cold anyway. cylinder temperature isn't going to get up to hot enough.

 

You will probably find that you have more power running between 180 and 200 degrees rather than 160. The idea is to keep the cylinder temerature as hot as you can but not so hot that it detonates. GM made the car run 200-225 degrees for emissions and gas milage purposes. To see the real benefit of a cooler thermostat, you need to add more ignition timing using a different PROM, or bumping up the base timing(not the preferred way). Anything below 180 will rob horsepower, and anything below 160 will most likely put the computer into open loop.

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89 Transam GTA, 350TPI, auto, 3.27 rear, dual cats, gray.
Magnaflow cat-back,
K&N open element,
Best E.T. 14.63@95mph

 

I agree with TransamGTA350, in fact, most of those "off-the-shelf" eprom (Jet, Hypertech, ADS etc) designed for a 160* T-stat are not even properly set up. There are a LOT of little settings that need to be adjusted to make the ECM work properly. In fact, even a 180* needs a few changes to make it work properly as GM designed the eprom to work with a 195* T-stat.