180 Deg Thermostat

[Mark Gilbert]

I can tell you first hand that the length of time the coolant is in contact has little to no impact on cooling. You want more volume/flow to fully pressurize the water jacket and keep steam bubbles from forming. The big block truck engines and later 6.5 diesels went to dual thermostats to increase coolant flow for more capacity.

I noticed improved power and throttle response running cooler in hot weather.

My brothers 99 Suburban and my 99 Tahoe both had the HD cooling systems with the 34" wide dual core radiator and 11 blade plastic fans. Neither ran hotter than 190°F with a 170°F thermostat and had great a/c. My express van had the tiny 31" wide single core radiator and 5 bladed metal fan. Even with a 170°F thermostat the Express would run 220-240°F in hot weather and the a/c sucked in town. I upgraded the radiator to a 454/8.1 1-ton Express 34" wide dual core unit and swapped over to a duramax fan blade on a Trailblazer SS fan clutch. It never hit 200°F on the hottest day, running WOT uphill for miles at a time towing my travel trailer.

You are on a lot of other forms with some variation of the screen name Fast305, right?

If so, your first hand knowledge means nothing to me.

 

[L31MaxExpress]

You are on a lot of other forms with some variation of the screen name Fast305, right?

If so, your first hand knowledge means nothing to me.

Your experience and lack of understanding of how basic physics work mean nothing to me because to me the proof is in the results I see.

When you run more coolant through the block, you eliminate hot spots especially in the cylinder heads. Between the cooler coolant and cooler hot spots it decreases the octane requirement. What this means is the timing can be advanced further than normally possible on 87 octane. I was running a stock L31 at 29° of total timing on 87 octane without knock retard. Stock tune does not even give 24° of timing and often has knock retard. That was also running leaner at 12.6:1 than the 11.2:1 air/fuel ratio the factory tune provides for a target. The factory ECMs also retard the timing over 190°F coolant temp in increasing amounts. The Vortecs also retard the timing anytime the IATs get over about 100°F. I also played around with a "HOT" tune that targeted a WOT air/fuel ratio of 13.2:1 and gave 32° of timing for a short period of time as well and used the catalyst overheat function to progressively richen back to 12.6:1 and retard the timing back to 29°. Gave another 10-15 hp for about 20 seconds. Knocked about 3 tenths of a second off 0-80 times. I could not have dreamed of doing that running at 210°F on 87 octane.

If you have a factory 11 blade fan, properly functioning fan clutch, the factory shroud and a clean 34" dual core radiator you have the best factory cooling system available. A 170°F thermostat and a flowkooler water pump are the best mods a person can make to the factory cooling system.

 

[df2x4]

You are on a lot of other forms with some variation of the screen name Fast305, right?

If so, your first hand knowledge means nothing to me.

If the response you got wasn't enough of an answer for you, yeah that's him. I agree with you too honestly. I know not everything he says is bad info, but it's really hard to believe anything someone says after you've seen them caught in a lie.

Fair warning to anyone not familiar with the story, L31MaxExpress was caught claiming someone else's dyno sheet as one of his own on another forum.

 

[Mark Gilbert]

Well, either way. You can call out my "lack of knowledge" however you want. Why don't we keep communications between you and I to a minimum, in fact zero... Anything else can be said in PM's

Back to the topic. My experiences have been quite different and my reasoning can be taken however you want. Putting a lower temperature thermostat in an otherwise stock vehicle does not help bandaid the actual problem. In fact I have seen it do exactly the opposite..

 

[L31MaxExpress]

Opening the thermostat sooner, allows coolant circulation through the radiator. As long as the coolant is cooler than the engine block and the radator tubes are cooler than the coolant heat will be removed from the system. Obviously higher operating temperatures will give the system increased cooling capacity to a point. However circulating coolant at an earlier point will slow the rate at which the systems temperature rises to equlilibrium. There are several factors in play regulating the maximum temperature. In the coldest weather you can cool an idling engine with only a heater core. In hot weather it would quickly overheat. Coolant flow rate, radiator surface area and air volume all play key rolls into how much capacity the cooling system has. If you leave the coolant flow alone and increase the airflow from a bigger fan you can pull more heat out of the radiator fins and thus coolant. If you increase the radiator area and keep the same fan you also increase the amount of heat removed from the coolant. Now if you increase both the fan and the surface area you can increase the coolant flow rate and move alot more heat out of the engine. I am going into Streetrod world for a moment. Lets take say a 1923 Ford T-Bucket with a 350. Those have a very limited area to put a radiator and its hard to get a good engine fan in them. Those cars will almost always overheat sitting around town idling but out on the road they run cool. At highway speeds you have cool air ramming across the radiator and the water pump is generating more pressure and flow on the system. I have actually played around with one of those cars specifically. It had a 0.080" over 350 in it. It liked to run HOT. I pulled the traditional short water pump off it. Installed a spacer/riser that uses a later GM I6 water pump. Pulled the 16" electric fan off it. Replaced it with a shroud and a mechanical clutch fan. I found a severe duty clutch that offered more fan rpm when it was freewheeling and a 150°F engagement temp. The car was a toy driven only in nicer weather. I pulled the thermostat out of the car and replaced it with a restrictor/spacer that had a machined opening to slow the flow of coolant. Car went from running 250°F on a 85°F day to maintaining 180°F even on a 100°F day. On the highway that car would actually drop down to 165°F.

 

[PlayingWithTBI]

IOW - it's all about thermal mass removing heat from the system. Air has less mass than the coolant so you need more volume of air. If the coolant is flowing faster it has less time to cool but, there is more volume being cooled. We had aluminum extrusion presses in which we were running 5 - 250HP hydraulic pumps and a 48" hydraulic ram running up to 3000PSI. We used tube-in-shell heat exchangers with evaporative water cooling towers to keep the oil below 135* (considered hot over that) usually 120* optimum. The press had a thermostat in the oil tank (~1300 gallons of AW68 oil) that would turn on and off the water recirculating pumps in the cooling towers. There is a lot of engineering and calculations that went into designing these systems and if the 4 - 250 SQ FT tube-in-shell exchangers got a little plugged the flow of water through them would, of course, slow down causing the temperature differential in and out to increase but the press would start overheating. If a ring in one of the cylinders wore down and started bypassing (causing more heat), the press would overheat. Bottom line the more water flow through the system the more efficient the exchange of heat. Part of the process was quenching the extrusion from over 950* to less than 350* IIRC in less than 1 minute to make tensile strength properties but, that's another equation about heat exchange with water (in this case R.O. so it won't stain the metal) and air volumes.

 

[Frankenchevy]

Your experience and lack of understanding of how basic physics work mean nothing to me because to me the proof is in the results I see.

When you run more coolant through the block, you eliminate hot spots especially in the cylinder heads. Between the cooler coolant and cooler hot spots it decreases the octane requirement. What this means is the timing can be advanced further than normally possible on 87 octane. I was running a stock L31 at 29° of total timing on 87 octane without knock retard. Stock tune does not even give 24° of timing and often has knock retard. That was also running leaner at 12.6:1 than the 11.2:1 air/fuel ratio the factory tune provides for a target. The factory ECMs also retard the timing over 190°F coolant temp in increasing amounts. The Vortecs also retard the timing anytime the IATs get over about 100°F. I also played around with a "HOT" tune that targeted a WOT air/fuel ratio of 13.2:1 and gave 32° of timing for a short period of time as well and used the catalyst overheat function to progressively richen back to 12.6:1 and retard the timing back to 29°. Gave another 10-15 hp for about 20 seconds. Knocked about 3 tenths of a second off 0-80 times. I could not have dreamed of doing that running at 210°F on 87 octane.

If you have a factory 11 blade fan, properly functioning fan clutch, the factory shroud and a clean 34" dual core radiator you have the best factory cooling system available. A 170°F thermostat and a flowkooler water pump are the best mods a person can make to the factory cooling system.

My L31 has a 195 tstat and runs up to 198. My WOT timing is 32 @ 12.8afr and my cruise timing is 36 @ 15:1afr...never detonates on 87 octane...

 

[L31MaxExpress]

My L31 has a 195 tstat and runs up to 198. My WOT timing is 32 @ 12.8afr and my cruise timing is 36 @ 15:1afr...never detonates on 87 octane...

Not quite stock but from memory I was at 9.6:1 SCR and had the 395' marine cam in it that results in about 8.2:1 DCR. The tune I ran driving down the highway unloaded or pulling my 6,000 lbs travel trailer was the same. WOT Timing was 32 @ 13.2 afr for about 15-20 seconds, then dropped off to 29 @ 12.6 Catalyst Overheat/Piston Protect fueling active. Cruise timing (not towing) was up to 48 at 17:1 afr. (NO EGR) With the 30.5" tall tire, 3.73s & 4L85E turning 2,200 rpm @ 70 mph it would net 19 mpg on long trips. On flat land it ran about 45-50 KPA and 18% TPS. Running a 170 stat (usually ran 178°F) it would run without the trailer on 87 fine, but needed 91 towing to keep it from knocking running hard in 3rd gear. I could have backed off the timing but would have sacrificed ~10% in torque compared to burning premium. At 3,000 rpm and 85+ KPA I had to retard the timing 6-8* to stop the knock retard. Down to 18 rather than 24-26. I wanted power. I drove it once foot to the floor in 2nd @ 70-75 mph into a head wind for around 80 miles. Didn't miss a beat.

 

[RichLo]

It had a 0.080" over 350 in it. It liked to run HOT.

I bet it did run hot, why would you ever purposely bore out to .080?? IMO, anything over .030 is yard art (junk block).

 

[wb292]

I guess I should have added more info. This spring I will be replacing the engine. It's got a lot of miles and is smoking. Putting the new engine together I was thinking of running a 180 because it can reach 120 outside in Mohave Valley. In the Summer. And I have a 6% grade for 18 miles to climb on my way home from work. I have a 6 blade 20 inch fan for it. I am also planning on going with a larger aftermarket all aluminum rad. At this point I am gathering parts. If I need to tow something I would like to have as much cooling capacity as I can get. Any ideas would help,