I'm thinking about putting a 170* thermostat in my IROC. I mainly want to extend the engine's life. (performance enhancements are always welcome, though) If I put the new stat in, what kind of changes am I looking at? Also, will I HAVE to adjust the cooling fans to turn on earlier, or will the engine be OK without cooling fan adjustments. I live in the Midwest where temps range from 5* in winter to 105* in summer.

1989 IROC-Z -- 5.7 L TPI -- TH-700R4 -- Hypertech Street Runner Chip -- AC Delco Ignition Wires -- Edelbrock TES w/ Dynomax Cat-Back -- K&N Filters -- AFPR (50 PSI)-- MAT Relocated -- All The Free Mods

 

It helps if you do the thermostat and fan switch mod at the same time, but you can do either one and come out just fine.

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1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.25 @ 107.18 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Webmaster: SoCal F-Bodies
-=ICON Motorsports=-

 

I USE to be a strong advocate of running cooler T-stats, but after seeing the effects of it (now that I am learn about the eprom), you are best to leave the T-stat.

Putting a lower temperature T-stat only "tricks" the ecm into giving more fuel, but it isn't necessarily the best thing to do. It really is a "fudge" on the ecm, when you REALLY need to burn a custom PROM.

From various articles I have read by various racing authorities (Smokey Yunick qualifies), they state that you want your engine as HOT AS POSSIBLE to get the maximum power out of your engine.

I understand the benefits of a cooler temperature on the TPI plenum, but the problem is the current GM prom anticipates a higher temperature CTS and coolant flowing through the TB. Putting a lower temperature T-stat (compounded with a TB bypass) makes the ecm run far too rich. You just waste gas and make your car possibly slower.

Trust me, until very recently, I was a strong advocate of a lower temperature T-stat, relocated MAT and TB Bypass. But I am now seeing that this is not a good thing.

PS: Just altering the fan(s) switch is not enough in the prom. You have to adjust the idle and the a few cold start tables if you TRULY want to run a lower T-stat. If not, the ecm thinks your engine is still cold, and you (again) just burn more gas.