tested hot engine without thermostat
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
Because the 180F unit would over heat the engine, the temps just keep going and I have to shut down. so I thought 160 might be better. I did check the 180 and it definitely was all open by 180. I think my answer is because I don't have the system pressurized. It is open to the atmosphere because i have the body off. This is what the guy at Napa told me. I am going to hook up the expansion tank tomorrow and see what happens. If so, then I didn't realize how important it is to pressurize the system.
The NAPA guy said that without pressurization the pump can cavitate leading to inefficient reduced flow and potential damage to the pump. I bet this is true because all pumps need a certain amount of pressure to work properly. This is called NPSH. But I bet this is more true of a very high performance or racing application. Not mine.
[QUOTE=7T1vette;1571490823]Billa... I think you mis-read my post. You're concept is correct--and is exactly the same thing I posted. We just said it in different ways. The stat 'regulates' by adjusting the amount of flow through the radiator--which allows the cooling system to cool more. If the stat stays open all the time, the system [obviously] runs too hot for the stat to ever regulate.[/QUOTE]
That is correct.
It's probably more about the assumptions regarding the cooling system. In a properly sized and running system, the coolant coming into the engine will ALWAYS be only a few degrees warmer than the air. If the coolant is entering the engine at 200 degrees, there is a major problem with the cooling system - undersized radiator, plugged radiator cores, broken pump, etc.
In a properly operating system, the thermostat will regulate the temperature of the engine within a temperature range. It will open when it heats up and let cool coolant in and close down as the coolant cools it below its rated temperature. It's as simple as that.
AWilson - once again, I stress that you don't have a problem. The engine is supposed to be at 195-200 degrees! In fact, the manual states that temps higher than the boiling point of water are in no way objectionable as long as you don't have a leak. That's why the redline is around 250. Below 180-190 and your engine wears faster...
In a properly operating system, the thermostat will regulate the temperature of the engine within a temperature range. It will open when it heats up and let cool coolant in and close down as the coolant cools it below its rated temperature. It's as simple as that.
AWilson - once again, I stress that you don't have a problem. The engine is supposed to be at 195-200 degrees! In fact, the manual states that temps higher than the boiling point of water are in no way objectionable as long as you don't have a leak. That's why the redline is around 250. Below 180-190 and your engine wears faster...
The 'downside' to the hi-flow pump is that, in order to move that much more coolant, the pump expends a lot more work than a standard pump. Thus, more heat is generated than with a stock pump. If the entire system is upgraded from stock...including the availability of useable ambient airflow to pass through the radiator...that should be no problem. Otherwise, a hi-flow pump will only cause the system to retain more heat than it did before.
There is increased flow on both the output and suction side of the pump.
You do have a problem. But, you can ignore it for a while if you want. No matter what anyone else tells you, a C3 with NO stat should stabilize at 160-175F; some small blocks with A/C (and with the A/C off) will stabilize at 140F. Since yours doesn't stabilize until 195F, it has a "capacity" problem...it can't reject as much heat as it should. But, since it doesn't overheat with the stat removed, you can get away with it. I assure you that, over time, that temp will get higher. Your first option would be to put some radiator cleaner through the system to rid it of collected scale and corrosion on the inside of the radiator; just flushing the radiator will not get that job done. That, alone, may solve your problem. Once you get it to where the engine will stabilize at something below 175F [or less], you can install the 180 (or higher) stat again.
AWilson
Are you using a "pressure balanced tstat"?
Is this a new rebuild?
Is this a radical engine?
What is the history on the radiator and fan/clutch?
Did you check the temps with a gun etc? If your gauge is 20° off, then everything would be proper.
Keep your timing total in the mid 30's and use the advance can.
If you aren't going to drive it for a while while putting the body back on, I would suggest putting at least 50/50 antifreeze in it to eliminate any possible corrosion inside.
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
Ok guys it's fixed and the NAPA guy, (Kid) was right. I changed nothing and hooked up the expansion tank so that the system could pressurize. I guess to be picky there was a change, I needed to add maybe a quart to fill the tank 3/4 of the way. So without the stat it stabilized and ran for at least a half hour at about 160. Then I shut it down and put the 180 stat back in and it stabilized at what I would say was 175. Hard to tell with that little gauge. So the 15psi of pressure made all the difference in the world. My new 383 with the original 40 year old radiator is running at normal temps. BUT, will it run hotter when the body is on and I have it under load driving it? TBD. Thanks for all the help. It keeps the ideas going until the solution somehow pops up.
Guess I type too slow.
Glad it all worked out.
Pressure is a wonderfull thing. Your NAPA kid is sharper than the experts.
Race Director
Joined: Nov 1999
Posts: 10,643
Likes: 8
From: Foxfield CO 1970 Convertible
OK - retroactive analysis... 
The previous statement is only true if the coolant can get higher than its boiling point, which won't happen in an open system. I think what may have been happening is that the coolant was "flashing" to vapor in parts of the block when the thermostat was installed. When the system was pressurized, this couldn't happen so proper cooling was restored.
Just my opinion...
He said that the pressurized fluid is more efficient at removing heat.
Just my opinion...
Advanced
Joined: Sep 2008
Posts: 72
Likes: 0
From: Essex
not wishing to state the obvious and I want to help,
your symptoms sounds to me like the radiator has seen better days, possibly silted up if more than a few years old, or maybe it has lost too many convection vanes...the little bits that sit between the tubes that carry air around the water carrying tubes.....
Also, your newly rebuilt engine has lot more friction until she beds in causing more heat so maybe this is why you are now seeing this assuming you have apples as apples and not mixed an orange in there...you haven't changed anything else....like got the fan blade bolted on wrong way around.....can you even do this on a C3.... I know you can on 1969 Ford Cortina X-Flow engine but that another storey:o
Don't run without a t/stat, this can cause localised hot spots in block and heads, as the back pressure in the system is reduced, look at some race engines and they carry a t/stat that is simply a drilled disc to keep back pressure within the eystem and ensure water 'wets' all cooling passages.
hope this helps
your symptoms sounds to me like the radiator has seen better days, possibly silted up if more than a few years old, or maybe it has lost too many convection vanes...the little bits that sit between the tubes that carry air around the water carrying tubes.....
Also, your newly rebuilt engine has lot more friction until she beds in causing more heat so maybe this is why you are now seeing this assuming you have apples as apples and not mixed an orange in there
...you haven't changed anything else....like got the fan blade bolted on wrong way around.....can you even do this on a C3.... I know you can on 1969 Ford Cortina X-Flow engine but that another storey:oDon't run without a t/stat, this can cause localised hot spots in block and heads, as the back pressure in the system is reduced, look at some race engines and they carry a t/stat that is simply a drilled disc to keep back pressure within the eystem and ensure water 'wets' all cooling passages.
hope this helps
