What thermostat to choose for 350 and quadrajet
 

guys,

my 350 seems to be running rather cold! about 145-150F.

the thermostat is closed at cold start, I checked that, and after a couple of highway miles it has opened and I can measure a temperature at the thermostat-housing of 165F.

I have been searching the internet and found:

ACDELCO says the standard thermostat is 195F for my engine

and I find some topics on other forums that state that the normal operating temperature would be 195-210.

is this correct?

what is the standard operating temperature of a SB 350

btw, I live in the Netherlands with an intermediate/sea climate. normal summers and winters.

Re: What thermostat to choose for 350 and quadrajet
 

Either a 180 or 195 either one is a good choice. Colder climate guys like 195 for a better heater output in the winter.
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Re: What thermostat to choose for 350 and quadrajet
 

I run a 195 in mine, and always have. That is stock for my '86.

Slonaker

Re: What thermostat to choose for 350 and quadrajet
 

I run a 210. I have not found any deleterious effects.

Re: What thermostat to choose for 350 and quadrajet
 

agree

Re: What thermostat to choose for 350 and quadrajet
 

thanks guys. I am gonna go with a 195F then!
thanks!

Re: What thermostat to choose for 350 and quadrajet
 

I agree with the higher temp thermostat.... may also make your truck run better.

Re: What thermostat to choose for 350 and quadrajet
 

Look on the copper part of the t stat u take out and see if it says 160 on it. May have had one in there.

Re: What thermostat to choose for 350 and quadrajet
 

My truck runs a 195

Re: What thermostat to choose for 350 and quadrajet
 

I would think over there in the winter you will never see 195* on your temp gauge.
Your engine will love you!!

Re: What thermostat to choose for 350 and quadrajet
 

:-)

Re: What thermostat to choose for 350 and quadrajet
 

195*

Re: What thermostat to choose for 350 and quadrajet
 

thanks!
I ordered a 195F and gasket yesterday. Will probably be in next monday!

I will report back on the result.

for now!

Merry christmass!

Re: What thermostat to choose for 350 and quadrajet
 

oke, got the thermostat today and replaced it (195F)

first disconnected the upper hose on the radiator. check out the dirt that came out. If you take into account that I just had the cooling liquid refreshed this summer. Shouldn't it be a lot less dirty?
http://lh3.ggpht.com/_i4YwYZutwgk/TR...0/DSC00180.jpg

http://lh3.ggpht.com/_i4YwYZutwgk/TR...0/DSC00182.jpg

I cleaned the thermostat houding and took a good look. NEver had this piece loose yet.
http://lh4.ggpht.com/_i4YwYZutwgk/TR...0/DSC00186.jpg
http://lh5.ggpht.com/_i4YwYZutwgk/TR...0/DSC00188.jpg

here you can see hoe dirty the cooling liquid is. about a quart came out of it. I tried to catch as much as I could in a little bucket.
http://lh5.ggpht.com/_i4YwYZutwgk/TR...0/DSC00193.jpg

when it gets warmer and the days are longer I am gonna have to rinse my cooling system....damn its dirty....previous owner probably had wather in it for a while I think? or never changed it...

these two bolts??? weer holing the thermostat housing. for now I reused them, but I want to change the housing and bolts this summer sometime.
http://lh6.ggpht.com/_i4YwYZutwgk/TR...0/DSC00195.jpg

anybody ever heard of Restone Thermostats? I got it at a local shop.

http://lh5.ggpht.com/_i4YwYZutwgk/TR...0/DSC00196.jpg

this bucket was clean when I started. Look at the dirt!
http://lh3.ggpht.com/_i4YwYZutwgk/TR...0/DSC00197.jpg
http://lh4.ggpht.com/_i4YwYZutwgk/TR...0/DSC00198.jpg

the old thermostat. Seemed to be a 180F.
http://lh4.ggpht.com/_i4YwYZutwgk/TR...0/DSC00199.jpg
http://lh5.ggpht.com/_i4YwYZutwgk/TR...0/DSC00203.jpg

the new thermostat, 195F
http://lh3.ggpht.com/_i4YwYZutwgk/TR...0/DSC00205.jpg
http://lh4.ggpht.com/_i4YwYZutwgk/TR...0/DSC00206.jpg
http://lh4.ggpht.com/_i4YwYZutwgk/TR...0/DSC00208.jpg

just cane back from a testdrive. Al stays dry. So that makes me happy. Now I a will keep an eye on the temperature the next few days and see if the engine gets warmer!

Re: What thermostat to choose for 350 and quadrajet
 

okay.
I did some driving around.

mostly 12km rides (about 7.5miles) the temperature goes up to about 155F on the gauge, so about 10K higher then the previous thermostat, but still thats pretty cool, dont you guys think?

should the temperature rise when you come of the highway after 5 miles of 60mph , stop at a traffic light and then drive about 3-4 miles though town? mine stays at 155F all the way through town.

Could this be my flexfan? constantly cooling at low RPM?

how can I check that the thermostat is not opening to early? I read something about closing the big hose to the radiator by hand after a ride and then letting it open up slowly and listening if you hear water running? is there no other visual check?

it is about 32F over here at the moment. could the outside temperature cool the engine soo much it doesnt get up to operating temperature?

Re: What thermostat to choose for 350 and quadrajet
 

Hard to say when your not running a stock cooling fan and shroud, as well as most importantly a stock fan clutch that wont have the fan kick in and hurt the mileage as well as not allow the temps to come up.

You need to use a cooling system flush kit and let it work for a good while to flush all that crap out of the cooling system.

Very hard on oil to not get it up to temp, tends to sludge up and break down very soon.

Re: What thermostat to choose for 350 and quadrajet
 

With the ambient temp. at 35* and 60mph you will be very lucky to get the engine up to temp of 195*. The gauge is telling you that 155* is as hot as it is going to get, try a peice of cardboard in front of the rad. and see if it will get hotter, BUT keep a eye on the temp gauge
Prestone is a good brand of thermo.

Re: What thermostat to choose for 350 and quadrajet
 

today after a little drive i checked with the IR thermometer. about 176F at the thermsotathouse and the same at the top part of the radiator.

this is the IR thermometer I am using:

http://www.ix12.com/shop/images/prod...A-311108_1.jpg

tech specs:
last time i checked, with old thermostat I got, 165F. So there is improvement. But still pretty cool.

And isnt it strange that the radiator is hot, while I only measure 176F and the thermostat is 195F....so the radiator should be cool, because the thermostat should be shut tight?

Re: What thermostat to choose for 350 and quadrajet
 

Thermostats don't shut all the way and always flow a little coolant even when cold.

Sounds like it is cold where you are and you need to use card board to cover the radiator if you want the full temp.

I would be perfectly happy with167*

Re: What thermostat to choose for 350 and quadrajet
 

Not sure if you are aware or not, but the heater core bypasses the thermostat. I see in the second photo of post #14 that one of the heater hoses is hooked up to the intake manifold water passage just to the left of the thermostat housing. Since you do not show an overall pic of the engine bay it is impossible for me to see if that hose goes to the heater box on the firewall and then a second hose goes back to the radiator as it is supposed to. Assuming it does, that is definately a path for coolant to flow and potential source of heat loss, especially if you have the cabin heater on while you are driving.

Re: What thermostat to choose for 350 and quadrajet
 

I know which hoses you mean!
they are for the evaporator of my LPG-system.

here's a overal pic of it. but thanks!
ignore the two red arrows please.
http://lh5.ggpht.com/_i4YwYZutwgk/TK...deze_slang.JPG

Re: What thermostat to choose for 350 and quadrajet
 

Those extra hoses are gonna cool it down a bit too, acting as an extra heat sink. To what degree I don't know, but I assume it would have to.

Re: What thermostat to choose for 350 and quadrajet
 

Im in miami and im not running a thermostat at all... Is that bad?
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Re: What thermostat to choose for 350 and quadrajet
 

Ditch the Flex fan and get a stock clutch fan..then it will warm up and you will reduce your chances of the fan coming apart and destroying your fan shroud and radiator. Flex fans suck.

Re: What thermostat to choose for 350 and quadrajet
 

Wow... guess it helps to have the whole picture of what you are dealing with. :lol:

Unfortunately it looks like there are a couple things going on. I think your number one issue is that LPG does not contain the same BTU's as gasoline. It is a known fact that an LPG powered engine will run cooler than the same engine powered with gasoline. Not much you can do about this.

Next, as previously mentioned the cabin heater and LPG evaporater are robbing some heat from the coolant. PLUS, they are allowing coolant to bypass the thermostat which will delay, if not totally prevent, the thermostat from doing it's job of regulating the temperature.

I am not an advocate of flex fans either. I have seen the damage they can cause when they explode. And I am sure that since it is not on a thermostatic clutch it is drawing air thru the radiator all the time which is compounding you other issues.

Personally, I think you need to do a couple of things. First thing would be to put a restriction in the heater hose line. I would use either a 1/2" ball valve or gate valve between the nipple on the intake manifold and the 'T' that split the flow between the LPG evaporator and the heater core. Or if you want, you could put 2 seperate valves after the 'T' and control flow thru each circuit.

Second would be to ditch the flex fan and get an electric radiator fan. You can control it with an adjustable thermocouple mounted to the radiator. This should help limit airflow thru the radiator in slow moving situations, but if you travel on the highway a lot then you may also need to block some airflow.