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 What thermostat 160 or 180
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Two Feathers

26 Posts

Posted - 09 Feb 2016 :  10:20:59 PM  Show Profile  Reply with Quote
For the 461 alluminum head 10.75 to 1 cr...do i use a 160 or 180 im in california so its hot and traffic..clutch fan

The Great White Buffalo

7235 Posts

Posted - 09 Feb 2016 :  11:04:13 PM  Show Profile  Reply with Quote
I always use 160's and then if you need more heat in the engine just swap up.

Bowties are for Pee-wee Herman. "Chevy": even the name sounds cheap, but not as cheap as your Pontiac will be with an LS transplant.
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Two Feathers

38 Posts

Posted - 18 Jan 2017 :  9:13:59 PM  Show Profile  Reply with Quote
Did I read That drilling a small hole in the thermostat flange will help stop air lock in the system ? just ordered a 160 stat and wonder if I should do this

What is the S, in Custom S ?
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Sitting Duck

1510 Posts

Posted - 19 Jan 2017 :  08:05:34 AM  Show Profile  Reply with Quote
I always do. It helps the block get the air pockets out when filling the cooling system,and there is no down side to it. I use an 1/8" drill bit.

I run a 160 degree in my GTO too BTW.

71' GTO Original 400 M20 3.23 posi
13.95@102.1 MPH on street tires

Edited by - 67drake on 19 Jan 2017 08:06:58 AM
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221 Posts

Posted - 19 Jan 2017 :  10:37:53 AM  Show Profile  Reply with Quote
I run a 160 in the 461 and the temp seems to stay in the 180 ballpark. That's with a cheap flex fan.

Robb Hermes
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Blued and Painted

3432 Posts

Posted - 19 Jan 2017 :  11:40:21 AM  Show Profile  Reply with Quote
Cooling and lubrication are closely related.
The viscosity of oil varies with its temperature. A 30 grade oil has a viscosity of 3 at 302F and thickens to 10 at 212F. It further thickens to a viscosity of 100 at 104?F and is too thick to measure at the freezing point of 32F.
The fuel system may like the cooler temps, but the engine oil needs to be near 212 for the least amount of engine ware.

Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.

Edited by - Blued and Painted on 19 Jan 2017 11:42:57 AM
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5361 Posts

Posted - 19 Jan 2017 :  12:24:25 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
I would prefer to run a lighter oil than run close to 210 all the time. I'd think heat kills more motors (and trans) than slightly too cool oil. But, i can see the worry, and i know modern cars love that 210 sweet spot for efficiency.
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