...Roger...

I use a 1/16 , probably smaller than other guys use but it works for me.

zzzhopperzzz

It never ceases to amaze me at how many folks don't understand "how" a cooling system really works.. The thermostat opens and closes depending on the temp of the water touching its underside.. Depending on the choice of temps typically from 160 to 195 it will open at the chosen temp. It will also close again the second cooler water touches its rear. Depending on the capacity of the radiator, it could be immediate closure or no closure.. If you have limited capacity in the radiator, the coolant will constantly circulate and become hotter and hotter. If you have "reserve" capacity, a larger radiator with proper airflow, the thermostat will close again from the cooler water from the radiator. (Thus the reheating of this water occurs in the engine AGAIN). The longer the water stays in the radiator, during the closed period, the more the temperature of the water, in the radiator will drop! Bingo, increased reserve! Not too complicated.. Colder thermostats? for what reason, they make LESS horsepower and you stand the chance of constant open thermostat (heat cycling).. 160 therms are for boats ect, that need a cooler engine compartment and have a great reserve to pull from.. (the lake)..

noonie

Check your pump first, if it has the bypass blocked off, some do, then your situation can occur, and you need to drill at least 3 1/8" holes in the tstat to circulate coolant before it opens. It also helps it open at the right temp.

toddalin

No idea where you get this idea. Dyno pulls continually show higher horsepower readings with cooler coolant temps.

ajrothm

+1

Dynoed my engine at temps ranging from 125* up to 180*..... made best power around 140-145*..... Thats the reality....Tested, proven on my engine.... Maybe not all engines are the same but....on my iron head engine, this was the case....It would lose 10-15hp at 160-165* and lose 20hp at 180*.... this on a 650+hp engine. Oil temps were kept in the 170* range or higher

This on a very controlled dyno session where we were continuously draining the hot water out of the tower after every pull and changing it out with cooler water to keep it at 140*.

Increased engine wear? Who knows but a cooler engine(water temp) with hot oil makes the most power....

73, Dark Blue 454

Now I see some are doing full bonzei dyno pulls on cold engines. This just keeps getting better and better.

jb78L-82

I am not sure what the confusion is here^ but it is well known that cooler running engines make more HP and not just a little. I ran my original L-82 4 speed for years with a 160 thermostat and big surprise that at 65,000 miles with 3.70 gears (3,500 RPM at 70 MPH), zero oil consumption! So much for the wear issue!

Also, currently, I run a 180 modified Robertshaw thermostat with a host of aftermarket cooling equipment and the car pretty much runs 175 degrees all day long. There is a VERY big difference in HP with my engine between its current temperature and it's OEM temperature of 225+.

I really don't see the issue about dyno runs on an engine running 160-165 degrees as long as the oil is hot-that is the critical component!

73, Dark Blue 454

So, if I swap from a 180-f thermostat to a 160-f and compare the two at the track (quarter mile) how much faster will my car go? 1/10 second? A half second? A full second?

Do tell.

ajrothm

Lots of variables with this...one being weather conditions but I would be willing to bet that if you were staged at the line at 160* and finished the pass at 170* or less, compared to staging at 180-190* and finishing at 200*+, you would likely gain 1-1.5 tenths...depending on the engine combo. Some gain more. Not to mention the propensity for detonation goes way down with a cooler water temp as does under hood temp, intake air temps....not to mention reduction of fuel percolation in the carb on a steaming hot engine.

On the street, I generally like mine to run 170-180*....

Remember, hot oil and cool water=most power.

73, Dark Blue 454

Trivia question: Anybody care to guess what the operating (coolant) temps are for the Nascar race cars?

Clue: It's not 160-f.

2nd clue: A typical Nascar radiator cap has a rating of 30 PSI vs. 15~ for our rigs.

73, Dark Blue 454

Here's some more documentation to explain that for a street rig, why your coolant temp needs to be much higher than 160-f.

http://www.streetrodderweb.com/tech/...nes/index.html

73, Dark Blue 454

Lower coolant temps don't help HP (see my Nascar trivia question above). A cooler intake charge does. Cooler intake (air/fuel) temps could result from a lower operating temp of the engine. That's been stipulated. But it's a poor way to go about making HP.

Reducing the temps of the intake charge by reducing the engine's operating temp comes at the expense of engine longevity.

So here's my challenge. I've posted several docs that support my statements.

I challenge somebody to find ONE credible doc that says a 160-f thermostat is ideal for street-driven our C3's.

Here's a good place to start: www.google.com

...Roger...

So ajrothm's dyno test showing more hp was a result of the intake manifold being cooler. Interesting. Thanks for taking the time to explain.

toddalin

Ever stop to think that your application of this NASCAR trivia is wrong and the reason NASCAR runs the temps and pressures that they do is because they have no other choice?

If you try to make 600+ hp for hours on end you will generate a lot of heat. Maybe they can't stuff a big enough radiator/cooling system under the hood to get these cars to run at optimum temperature for power. Even if they could, how effective would the system be in drafting situations?

But if they slap these engines in boats where they have all the cooling in the world (i.e., the ocean), do you think they would still run those temps?

Look at the temps that power boat racers run at who can run at pretty much any temp they like regardless of power level.

toddalin

Helps a bit, but goes beyond that.

ajrothm

No way....my engine was dynoed in a relatively cool dyno room with ventilation, it was pretty open had fans blowing in there. My intake was never getting too hot anyway, regardless of the water temp. We were making pulls 15-20 mins apart so the engine oil and surface temps really didn't have time to cool. We we dumping the coolant tower after each pull so we could refill it with cool water, then warm it up to 140-145* to make a pull. Oil temps were kept in the 170-180* range. We were keeping every pull exactly the same once we figured out what water/oil temps made the most power. Not sure why exactly cooler water temps made more power....maybe it was due to the iron heads, maybe cooler intake or whatever...but it definitely did make more power at a cooler water temp.

noonie

Can't compare.

Almost all salt water boats come with a 140° tstat and likewise freshwater boats come with a 160°. These tstats open at that temp and continue to open for another 20°.
The actual acceptable running temps in both cases ends up being from 160° up to 185° under full load.

Marine manufacturers are fully aware that marine engines will wear much faster than their automotive counterparts because of the temperature difference. The industry average for a pleasure boat is only 50 hours.

The desireable operating temp for marine is 180° the more expensive boats are equipped with "fresh water cooling" so the engine can use antifreeze etc, just like a car.

toddalin

This has nothing to do with temperature. This has to do with not pumping salt water through your engine vastly accellerating its interior deterioration.

I've had pleasure craft and in fact traded a boat for my Corvette. We ran a 160 degree thermostat in that (351 Ford Winsor) and it was just a car thermostat.

noonie

It has all to do with temperature.
Salt creates deposits at over 145° as do other contaminants in raw water cooling whether sea water or fresh water.
Most boats run closed engine compartments, lots of contained heat.

They run colder for these reasons, not for increased power as you suggested.
That’ why I said you can’t compare.

Here in Ft Lauderdale, almost everyone I know owns a boat, as I do, and given the choice, they opt for fresh water cooling with higher than 160 running temps.
My former neighbor builds marine racing engines for a living. If some customers run raw water cooling, he increases the piston clearance amongst other changes. It’s purpose built.

zzzhopperzzz

Wow, I thought most anyone knew engines of the gasoline type become MORE efficient as they heat up, (up, to a point)... More efficient = more available horsepower.. As for boat temps, you picked the right one to "pick" on. I've built over a thousand freshwater boats and worked for Viking in St. Pete on their "Super Hawaii" project.. The engine temps are kept low NOT for horsepower reasons or corrosion reasons.. Heat buildup is VERY dangerous on any boat, it causes gas fumes to do funny/dangerous things.. Like creep up the sub-floor.. Most all factory boats come with a 160 thermostat for this reason.. (to lower engine compartment temps).. Zinc diodes take care of the corrosion problem.. (Both in and out of the engine) You might notice that the thermostats in most factory boats are of the stainless sort also.. I've noticed a huge "response" difference in cold vrs hot, (160 vrs 195), hot always has better response..