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160 Degree Thermostat in an 8.1L?

bcfitzsimons

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bcfitzsimons Enthusiast

bcfitzsimons

Posted
Posted

So I have this 160 degree thermostat I got off the internet for my 8.1L-

 

Has anyone tried a lower-temp thermostat in their 496?  If so, did it trigger a SES light?  Does your heater work OK?  

 

Thanks-Fitz.

Woody1 Enthusiast

Woody1

Posted
Posted
I cant help you out on the 496, but when i put one on my old 5.3 w/K&n, hypertec'd,gibson cat back, and then went with the 160 stat, I LOST 2 mpg, and didnt notice any improvement in power. Didnt make any lights go off, as hypertec asks when programming, if one has the stat on the truck. It was a Graniteli stat that I put on. I will not put one one my 8.1. hope this helps some....
CMNTMXR81 Senior Enthusiast

CMNTMXR81

Posted
Posted

Is it a homemade one?  Otherwise I have yet to find one for the 8.1 and I've been looking at least once a week.

 

Running a cooler T-stat won't trigger a DTC (Diagnostic Trouble Code) therefore not turning on your SES light.

bcfitzsimons Enthusiast

bcfitzsimons

Posted
  • Author
Posted

No, I bought it from Kenne Bell Superchargers.  Whipple Superchargers also sells 160 thermostats for the 8.1L.  I didn't call Whipple, though-Kenne Bell's price was $8, and I figured that I couldn't go wrong with that.

 

Now, in theory, running a cooler stat will help prevent engine wear.  But, is there a point where the cooler you go, the more engine wear you incur because the engine never really warms up?  And if that's true, would 160 degrees be TOO cool?

 

Fitz.

CMNTMXR81 Senior Enthusiast

CMNTMXR81

Posted
Posted

If Kenne Bell has them, I'm ordering one RIGHT NOW!  :D

 

I've been wanting to run it cooler for like 6 months!

 

As to running too cool.  AS long as you run it long enough, it'll burn off the bad stuff in the oil.  160, 180, 200 degree coolant temp isn't going to matter all that much.  The oil will reach operating temp regardless of coolant temp.

 

If you run your truck 5 minutes a day going to and from work, it won't matter whether you have the stock 210 degree t-stat or a cool 160.  It won't get hot enough either way to burn anything off.  Especially as it gets colder out as it will in Cleveland as it does here in Chicago.

TxDoc Senior Enthusiast

TxDoc

Posted
Posted

While not exactly the same difference, I read  this information on the LS1 site about changing thermostats and thought it may help you:

 

 

The LS1 guys had the 160 vs 180 thermostat issue come up and the recommendation was:

 

"The 180 thermostat will not change your temperature much at all, so if you want cooler running temps go with the 160 thermo. In order to take full advantage of a colder thermostat, you must have your fan settings set to come on sooner. A thermostat opens at the given coolant temperature (i.e. - 160* for a 160* thermostat), sending coolant to the block earlier or later. It does not directly lower operating temperatures. With the stock fan settings and a colder thermostat, the engine will run cooler on the highway, but as soon as you get stuck in traffic, even for a short time, the temp will creep back up again."

 

and

 

" I put a colder thermostat in my car and the gauge reads the same temperature as before! What happened?

 

Answer: If you've taken the steps to modify the fan settings (such as the HPP3) then you should see a difference in the temperature gauge if you have a 98 F-body. If you've got a 99 or newer, you must keep in mind that the gauge is not accurate enough to show a drop in running temps. It is set up to go to a preset level and stay there even if the operating temperature varies by 15-20F. The 98 gauges will fluctuate as the temperature goes up and down, and GM felt that new car owners might be alarmed with this happening. In essence, the 99 and newer coolant gauge is little more than an idiot light."

 

 

How can I modify my stock thermostat to open sooner?

 

"How to make your own custom Thermostat

http://www.ls1.com/customthermostat.htm

 

http://www.ls1.com/customthermostat_files/image001.jpg

 

The thermostats on the 98+ LS1 engines are designed in one piece which includes the outer casing.

 

http://www.ls1.com/customthermostat_files/image003.jpg

 

The Thermostat can easily be dismantled by twisting out the upper portion that holds the springs down as shown.

 

http://www.ls1.com/customthermostat_files/image004.jpg

 

The wax which controls the opening and closing of the thermostat through it's expansion if inside the casing. You'll notice the channel at the bottom of the casing.

 

http://www.ls1.com/customthermostat_files/image005.jpg

 

Here you can see how the plunger which controls the opening and closing of the valve falls into this channel.

 

http://www.ls1.com/customthermostat_files/image006.jpg

 

To make the thermostat opening earlier it is quite simple. All we need to do is make the plunger longer causing the wax to open it earlier. This can be accomplished by placing a spacer at the bottom of the channel where the plunger sits. People have found that using a spacer of .06 - .09 will yield a thermostat which will open between 172-180 degrees."

 

 

 

 

hope that helps.

CMNTMXR81 Senior Enthusiast

CMNTMXR81

Posted
Posted

I'm well aware of that, remember I have a heads and cammed LS1 that I've crossed this bridge with.  My LS1 has a 160 degree t-stat and I have my low speed fan set to come on at 165 and my high speed fan to come on at 175.

 

On our trucks fans turning on and off aren't an issue since they are pulley driven and always on.

bcfitzsimons Enthusiast

bcfitzsimons

Posted
  • Author
Posted

It probably will suffer 1-2 MPG-then again, that's about 10-20% of the mileage I get now.  But, if I was worried about mileage, I wouldn't have bought an 8.1L V8-

 

I just can't imagine how running the coolant temp lower could possibly be BAD for the engine.  Especially the big blocks with mechanical fans.  I'm just wondering if the fuel injection will go into closed loop mode, or if the coolant temp needs to be 195 degrees for that.  Fitz

CMNTMXR81 Senior Enthusiast

CMNTMXR81

Posted
Posted

Really fuel economy should be unaffected if at all minimally.

 

GM runs them so hot on purpose to burn off any potential left over hydrocarbons that *may* still be present for emissions purposes.

 

I ordered mine, it'll be vehicle number 100,301 in my driveway to have a cooler thermostat in it with nary a problem, my cooling system will last a tad longer and I'll be happier as I can run more aggressive fuel and timing curves now and especially when I do a blower and/or heads and cam (when it'll be a necessity) for optimal power.  :D

 

It really isn't all that big a deal.  It's simple (especially on 8.1's to replace), and can only help performance'wise.

rlchv70 Enthusiast

rlchv70

Posted
Posted
Keep in mind that metal expands and contracts with temperature.  These engines were designed to operate at 200F.  The clearances were set towards this goal.  Lowering the operating temperature will increase the gaps.  This will let more fuel blow by the rings, it will increase the amount of oil consumption, and it will increase the amount of wear.  On the other hand, it could increase the power due to a lower inlet air temperature and it can reduce the amount of frictional losses.  These gains may be offset by the decreased efficiency.
CMNTMXR81 Senior Enthusiast

CMNTMXR81

Posted
Posted

Never had a problem with such.  Metal will still expand at 160 as it will at 200.

 

All in all, the one motor I tore down after I switched to a 160 degree t-stat, the machine shop thought was a brand new crate motor I was building and even after doing all the work I did, I still managed 23mpg vs. the 26mpg I got before.  But in the process, I gained around 80+ rwhp, cut my ET's by nearly a second and increased my trap speeds by about 8mph.  Hmm, that 3mpg loss is killin me!

 

I fail to see any problems with doing this.  You're going to have to do it eventually anyway if you plan on running a blower or doing an agressive set of heads and cam.

bcfitzsimons Enthusiast

bcfitzsimons

Posted
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I have to agree with CMNT.  The actual degree of heat that the pistons, valves, cylinder walls, rods, and crank sees is much higher than 160 degrees or 200 degrees or whatever your coolant temperature is.  The fact that any water that hits the block on the outside turns to steam is testament to that.  Additionally-in terms of clearances-piston-to-bore clearance, valve seat clearances, etc. are all at-tolerance within the first minute or two of the engine running, simply because of the sheer amount of heat that's contained within the cylinder itself.

 

The only thing a lower temp thermostat will do is allow the cooling system to remove any additional heat generated by the engine that wasn't able to be removed by a 200 degree thermostat (up to the system's capacity, of course).  That heat has to leave somehow-whether that be by radiation, through the oil, through the exhaust, or through the coolant.  I'd rather it leave through the coolant.

 

Fitz

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