The Stovebolt Site Forums The Shop Area Engine Shop Inital start up - Thermostate opening...

My 1970 w/ a 292 has to practically overheat, before the thermostat opens..I have tried a 180-195 & there does not seem to make a difference. Once the thermostat opens the needle on the temp gauge stays in the middle...This only happens after the truck sits over night. once its used through out the day all is fine....

Try putting a T fitting in both heater hoses, with a small tube like a 1/2" diameter connecting them. This will create enough coolant circulation through the block during warm up to prevent hot spots from forming before the thermostat opens up.
Jerry

My 250 used to do that, it would climb right up the gauge, open, then cool off and run just fine from there on out. I believe I cured mine by moving the temp sender probe to a port right under the thermostat. It was mounted in the head between #1 and #2 cylinders. I suspect the water gets much hotter there, fooling us into believing the engine is overheating. The probe gets a much more even temperature where it is now. The 250 and 292 heads are the same, and I have heard the 292's run a bit hotter in the cylinders.

Joe

My Blazer would do that before I drilled an 1/8" bleed hole in the thermostat flange.

OK - Will try to answer all...How about I by pass the heater core all together ? - also I'll check & see where the temp sensor is...In other words the sensor is getting a false reading??? - Not sure about the bleed hole?

Ever wonder why all of these quirks never happened when these trucks were new? I remember back in the day I worked for an Olds/ Cad dealer & we had a 68 C-10 service truck, Nothing ever went wrong with it...& trust me it didn't get much love... Thanks for your input....

If you want to endure those yamdankee winters with no heater, go for it- - - -there's a reason people in Tennessee live here, and it has something to do with snow only sticking around for a day or three at a time! Just run a loop hose to circulate the coolant back to the water pump inlet from the heater outlet fitting. If the heater fittings are simply blocked off, it will create dead spots with no circulation and make the tendency to overheat more severe.
Jerry

I had the very same symptoms as you describe. I drilled a 1/8" hole in the thermostat, end of problem.

Ah..Don't use the truck in the winter, it sleeps in a shed...Not that it makes a difference but its a C-30 dump...Now there's 2 votes on drilling the 1/8 hole in the thermostat flange..Just can't imagine it would make all the difference, hoping to be proven wrong....What is the logic in drilling the tiny hole?

It supposedly prevents an air lock from forming in the upper radiator hose. It's mostly a "feel good" maneuver for people who don't want to go to the trouble to create a useful bypass to keep the coolant circulating past the cylinders before the thermostat opens.

Most good-quality thermostats have a jiggle pin built into them to accomplish the same thing without drilling any holes.
Jerry

Not all thermostats have a jiggle pin built in to them and I suspect yours doesn't.
The hole in the flange does two things.
First, it prevents an air pocket when first filling the engine.
Second, in yours and my case, it lets a small amount of water past the thermostat when it is in the cold/closed position. This allows hot water to reach it sooner preventing the spike in temp.

I'm familiar with the jiggle pin and will pull the housing to check it. If its not there I'll just drill it, as I know the thermostat works fine...Thanks for the tip

I don't know how old the 160 degree thermostat is in my 49 216, it came in it and worked great when I got the engine running.
Later I changed over to a 180 to try and do away with cold weather condensation (I drive it year round) and it didn't help that and made the engine run hotter (naturally) so I put the original 160 back in. The engine never gets above the "8" in 180 on the gauge and hasn't lost a drop of anti freeze since I added the overflow tank.
The original 160 has the small hole in it and the new style 180 didn't.
I close my heater valve in the summer and it doesn't cause any heat problems.
Just and FYI.
Heres a picture of the thermostats side by side.

BIG difference...

Volunteer fan (can't decipher the dt), Are you saying that the solid brass accordion-style t-stat has a factory made hole in it?
Carl

Carl, dt = Dave T

IIRC it's a Robert Shaw thermostat and yes it has a small hole in the cover plate which would allow air and/or coolant to pass through it when closed. I imagine it came that way from the factory.
Ironically Robert Shaw used to have one of their factory/plants here in K-ville over by the university. That thermostat was probably made there and it's been in the 216 since at the least 1969 as that was the year it was parked and slept until I awakened it a couple yrs ago.

re. Volunteers, they're picked to win the SEC east this year, been along dry spell.....

At least as far back as 1946 the owner had a choice of the 160 or 180 thermostat.

Alcohol based anti freeze would boil out to fast with a 180 thermostat so people ran a 160. With those that ran ethylene glycol they were able to run 180's.

Now as to condensation. Even if we ran 200 thermostats there still would be water condensation.

You see when you put in air (nitrogen, oxygen) gas (hydrocarbons) and if perfect combustion happened out of the tail pipe the nitrogen would not combine with the oxygen and no NOX would be formed. If there were no traces of sulfur in the gasoline no sulfuric acid/acid rain would be formed. Then if all the hydrogen and carbon and oxygen would combine H2O + CO2 = Carbonated Water.

If you ran your car in Italy you would have San Pellegrino water coming out of the tail pipe.

So engines produce water as a byproduct of combustion so putting in a higher thermostat will not stop the production of water inside the engine.

Though a higher thermostat will better help to vaporize the harmful byproducts of combustion thus making removal of them from the internal areas of the engine improving crankcase ventilation and dilution and slowing the break down of the engines oil.

Also a warmer engine vaporizes fuel better. Un-vaporized fuel tends to condense on it's way to the combustion chamber, does not burn well, resulting in more gas getting past the rings into the combustion chamber, into the oil. As well as wasting fuel.
Jeffrey

Let's remember that a thermostat establishes the MINIMUM operating temperature of the engine- - - -the size and cleanliness of the radiator and the airflow through it controls the maximum temps. Ambient temperature of the surrounding air and the load the engine is pulling will have somewhat of an influence, but keeping things cool is mostly a function of how much heat the radiator moves from the coolant to the surrounding air. Copper is a much better heat conductor than aluminum, so it you choose to use a modern aluminum radiator, be sure to upsize it a little.
Jerry

Good stuff. I did a post on my battle with excessive cold weather condensation a yr or so ago and lost. The conclusion was the bottom end, i.e. piston/rings had too much blowby which carries all those combustion byproducts upwards into the valve cover as opposed to down and out the draft tube, which I had modified to a PCV system to try to force those byproducts to flow that way. It didn't and doesn't although I have very good suction to the intake manifold at most all rpm.
Thankfully the blowby has decreased quite a bit with more usage to the point of the valve cover vents aren't smoke stacks at idle anymore.
As an aside, I get no noticeable condensation accumulation in the valve cover in warm weather....

Question, with high quality moonshine now being legal here in TN, what byproducts could I expect should I add some to ethanol free gas? Spiked avion water perhaps
j/k

Dave

Problem solved !!! - Drilled two 1/8 holes on the thermostat flange and the temp gauge went to about 3/4 at an idle, after I reached my destination...On the return trip it was at 1/2 or mid point on the gauge...and we all know how hot it is today ! - Thank you all for your input...

Glad to hear!