I know this topic has been discussed over and over again but this week it has been very hot. In the 85 to 90 range with high humidity. I decided to experiment with thermostats. I can pull my thermostat in minutes when the engine is cold. I siphon a littel antifreeze out of the rad, and the thermostat housing bolts are well used and lubed.
I also monitor head temperature in each head. My thermostat basicly came out or went in every time the car went out.
I found this.
The final running temperature if anything was a little cooler without the thermostat although it did take longer to warm up.
I did not see the overshoot of the thermostat opening and then the temperature dropping after it opened. I did use 2 different new thermostats. One 160 and a 180.
The most important thing for me was head temperature. When I stop with a warm engine for say 5 minutes like a gas stop the head temperature soars to over 230. With a thermostat it take many miles down the highway before this temperature drops back down to normal. Without the thermostat the head temperature almost immediately drops back down. Certainly within a mile.
For me a big believer in thermostats. I will maintain a good thermostat in my work vehicles but in my vet who is only driven in nice weather it is gone for good.
No more worries about a malfunctioning thermostat and quicker head quenching.

 

Interesting post, I'd never thought about the "heat soak" being different with/without a thermostat?? Will be interesting to see other replies too!

 

Norval

Do you run your vette in cooler weather? Maybe the answer is to take the stat out in summer and put it back in in the fall. I like to start my car in the winter just to hear it run and dream of summer days. Drive it on a occassion too if the weather permits. Only problem I see is that my car runs best at 180 to 200 and if it gets cool out in the evenings it will most certainly drop below that. Any tests on flow rates of stats and pumps? A high flow pump and stat combo might help. How about plumbing the heads? I see some of those stat housings with radiator cap fittings have tapped holes for plumbing heads, this would by pass the stat and allow more coolant to flow through the heads.

 

I am not going to do anything to my cooling system. I have a large aluminum rad, a high capacity aluminum pump and twin tornado 16 inch fans. I do not have a heating problem but I wanted to know so out came the thermostat, back in, back out etc etc.
The head heat soaking is what sold me for the hot weather. Sure I can put it back in when it cools off. In fall the car goes into storage and is stripped down, at least part of it. The valves are backed off etc etc. I do not start it until it is time to bring it out.
So 2 highlights came out of this.
1 It did take longer to warm up but the final temperature was no higher then with a thermostat, maybe a bit lower.
2 Heat soak dissapated alot quicker. Within a mile without the thermostat and many miles with.

If it gets cool in the fall and I am still driving I will put it back.

 

Is any of this information pointing to just using waterneck restrictors rather than a thermostat?

 

I've never noticed the delay in temperature drop from heat soak, and my sensor is in the head. I do run a Robert Shaw high flow stat which has a significant higher flow rating. Maybe I have the best of both worlds..

 

Kinda what I was thinking. I would like to see some test flow data on stats to see which has the highest flow rates. Seems I have seen some advertised as high flow.

 

I pulled the thermostats out of both of my "summer" only drivers. I haven't had a problem that I am aware of. I just feel that I get better cooling flow. Nothing to back this up, just that I fell better without a thermostat!

 

I certainly don't have the answers and I haven't thought about this too much, but...

What is the advantage in the head cooling down quicker? Stops detonation?

Also, I would think quick swings in temperature (either up or down) would be a bad thing. Is the thermostat maybe designed to keep the heads from cooling too fast?



[Modified by jerryp58, 1:52 PM 7/9/2002]

 

With a thermostat my left head cools down quicker then my right head. I have sensors in both with seperate meters. The passenger head stays hotter after heat soaking longer then the right.
I am not trying to start a debate all over agian just posting what I found out and feel about running without a thermostat or restrictor. While I have never in the past run withou a thermostat and believed in them strongly I am changing my tune after repeated trying with and without. I feel without nothing can go wrong and since the engine temperature is no higher and I notice the right head cooling off just as fast as the left I say in hot weather why bother with a thermostat.
Once agian in my daily drivers no way I am going to run without but in my play thing I will leave it out for now with confidence that I am not hurting anything and upping the reliability.

 

norval
what pressure is the cooling system with and without?
i have a psi gauge on the dash and mine runs 14psi.
the reason i ask is i thought the thermostat pressurized the system, but i never checked.
maybe without the pressure is lower; boiling point is lower
then again, maybe not
:troll

 

Pressure increases the boiling point, think pressure cooker. I would image by eliminating the stat you will build more pressure from the stat housing to the waterpump inlet since there is less restriction at the housing. This might cause leaks if that part of your system is not up to snuff.

 

Living in warm climates, I've punched out the guts of a thermostat and run it as though it were always open. This eliminates the chance of failure while supplying the restriction to keep the water up in the heads.

 

I have seen conflicting info on flow rate through the heads. Seems if it flows to fast through there, it won't have time to dissapate the heat but I have no idea that the ideal flow rate is. I just think why do they make those stat replacer restictor plates if slowing the flow down and increasing pressure is not good for heat transfer? I just like the idea of the engine heating up faster and staying above 180 since my engine likes that temp or it runs a little sluggish until it hits it. I guess each engine is diff.

 

The main reason for a thermostat or restrictor is to increase the pressure in the block. With a good balanced flow high volume water pump like a GM 14011012 or a Howard Stewart Stage 3 pump you will see a pressure increase of about 10 to 12# on the block side over the radiator side at higher RPM. The benifit of the higher pressure is to stop localized hot spots in the heads. I have done numerous dyno test on a Superflow dyno where I placed 8 temperture sensors in the head. With no restrictor there was temperature variations of up to 55°. With a restrictor there was temperture variations of only 30°. (All test where done on a small block, Big blocks would be different as they do not have siameese center exhaust ports.)

If you heat a frying pan and then put a drop of water in it you will see that the water will try to move away from the hottest part of the pan. That is what happens inside of a head. The hottest part of the head is between the two center exhaust ports. Without pressure water will push away from these areas causing them to keep getting hotter and hotter even though the water temp guage reads normal. This leads to detenation. With a restrictor the pressure on the block side of the pump is increased pushing water to these local hot spots. On race motors I will plumb an additional -6 line to each cylinder head directly from the water pump to try to keep the temperatures down in this area.

One a street motor where you are at wide open throttle for only a few seconds it probably won't make a difference one way or the other, but if you are on the throttle hard creating a lot of exhaust temperature I would not run without some type of restriction in the thermostat housing.

 

Thanks Pete

That is very good info. I'll keep running with the stat.


[Modified by Fevre, 9:06 AM 7/12/2002]

 

Thanks Pete, btw nice web site. Are you sticking with those sidepipes or going to duals with your new engine.

 

This car is going to stay the way it is, stock L-82. I have been looking for a project car to put the motor I am collecting parts for in. It is going to be an all aluminum 420 with 18° heads so my header choice will be limited.

Right now we are building a new dyno room so everything is on hold until we get that done. Probably be over the winter before i get back to the motor.

 

Pete
That is some real eye opening testing that you did :cool:
It would be great to see it on your web site :yesnod: How about it?

 

Good post guys, lots of good information.

I have used a restricter in our old drag car years ago and it worked well as stated above.

I have also always wanted a manual overide thermostat that used a gooseneck with a bolt threaded down from the top. This way in the summer or if the dang thing stuck closed it could be manually opened. Or I could over ride its thermal closing function by screwing it open and leaving it open. It would then operate as the restrictor plate creating pressure, yet still have the option of returning to an operating thermostatic control.

Oh yeah, put an O-ring on the bottom of the housing for me too.

Well wake me up, Duh, I know it's impossible to have something like this in the real world...........JIM :smash: