It's OK...we can agree to disagree. The "always" in your statement [especially for a closed-loop system] is certainly a bold one. As I stated, if the cooling components can't reject as much heat as the engine/pump is generating, the system will continue to overheat. There is a problem in there somewhere...and my approach would be to 1.) check the thermostat and its operation; 2.) clean out (not flush) the radiator to make sure it isn't limed up; 3.) make sure you don't have a restriction/blockage in the system somewhere. Good luck with finding your problem.

 

I definitely should have said faster flow "will never cool worse" rather than "will always cool better" as it is definitely a decreasing return. Yes absolutes are dangerous but you'd have to be putting some serious power into a water pump to outrun the benefit of faster flow.

I don't mean to disagree with everything you said, I was actually responding to your ~2nd post and ended up below another post. I just wanted to clear up the common 'flowing too fast through the radiator to cool' misconception as I've previously believed that myself and seen it disproved.

 

first off i want to say i'm impressed with the quality of the feedback, there are some very smart people on this forum.
second i'll try to answer a few questions that came up. the 502 was a long block ,with an edelbrock hi flo pump added , the former owner will provide part #s for the pump & rad when he returns from a trip thursday or friday, the fan cfm rating is 2500.the car was always a big block car, oe it was a 454,all body parts are original , no front end mods of and kind.
third,after reading 69427's post ( 3 or 4 times to really digest it ), GREG454's post about an 8 * temp drop and LIVE&LETDRIVE's post ( had to read his a couple of times too),i'm starting to rethink some of my previous assumptions(not to mention getting a headache, i haven't done this much thinking in a long time).
fourth,live&letdrive,i have toyed with the idea of a restrictor, as a matter of fact i turned one out the other day and the only hold up was what size hole to put in it to start with , you indicated that is a bad idea, if so would it be useful to try and diagnose , or just a bad idea all around.
thanks again for all the thought and effort you guys have put in this,
don

 

This should show that a high flow pump is usually better. Be aware that once turbulent flow is achieved, a higher flow will return diminishing results.

Perhaps LiveandLetDrive can explain better than I, the relationship between pump gpm, coolant velocity (in ft/sec) and restricters without disclosing any company secrets.



This is true not only in the radiator, but also in the engine as 69427 pointed out with the steam pockets.

If, you are lucky, your solution might be as simple as this.
The first thing I would check is the type of tstat you are using.
A standard tstat can have a tendancy to shut as rpm increase because of the increased flow and their inherent design. You seem to have those symptoms. It would still test fine in the boiling water test. You should run a pressure balanced tstat as in this picture and available at Advance auto. You have to ask for it. Cheap enough.






Secondly, try running at least a 180° tstat or even a 195°. You said you were running 185 normally, but didn’t mention what temp it creeps up to. Trying to run a 502 in a C3 at less than that might be a dream in Florida. I’m in S Florida and in 1 C3 I run a 180 and a 195 in another, both with Stewart Stage 2 pumps and have considered going back to stock pumps because I am running colder than I want, but they are basically stock engines. I use those pumps with the stock radiators because of the added ambient temp caused by the a/c condensers which here are used all the time.

Third, at operating temp (195°) a new aluminum rad should see an inlet/ outlet temp difference of around 20° with a fan speed of over 3000rpm. This is assuming your cooling system is clean throughout.

 

i'm currently running a 160* standard t-stat. the highest temp i have seen is 210,( you know about those long s fla traffic lights) i would be an idiot not to at least try a balanced 180* t-stat , will do that asap.

 

Yeah the coolant has more time to cool, BUT the engine has more time to heat up the coolant in the engine. The net result will always be warmer coolant. The engine's hot surfaces will add heat faster than the radiator's ambient air temperature surfaces can remove that heat.

If slowing down the coolant were to help, then why not slow it down to ZERO? Give the coolant in the radiator all the time it needs to cool down to ambient temp. At the same time, the coolant in the engine is superheated steam. I hope no one really does add cooling system restrictions.

I do agree that the convective coefficient between the coolant and the inside of the radiator is a "diminishing returns" sort of thing. At some flowrate, it won't get any higher, whereas the power it takes to move the higher flow will always be more-or-less linear with flowrate. So I'm not advocating driving the water pump faster, just, don't add any unnecessary obstructive bull**** in the coolant loop, no matter how compelling the marketing brochure is.

Not saying this from my degree in mechanical engineering, but rather, from life experience. Partially opening thermostats, crapped up radiators, blockage in hoses, etc. ALWAYS work AGAINST the interests of keeping the engine cool. NEVER have I had a cooling system obstruction that made me say "Hey, this guy's running cooler than it did when new!"

If it wasn't such a parasitic power loss, I'd have the coolant going ten times faster than stock, to achieve highly turbulent (Reynold's number > 2000) flow.

 

lots of therory here, let me give everyone a fact.
I personally built a Super jet boat motor, that kicked *** it ran great !
unfourantly, It ran cold lake water into the motor for cooling,
with no type of restriction for the water leaving leaving.

We burnt the motor up completely, due to no restriction in the cooling.
After much debate and reveiw by lots of experts, it was decided
the water did not stay in the motor long enough to absorb the heat.

Built a new motor, added the proper restrictions, and no more problems.

so yes you can have too fast of flow thru a motor.

just like you can have to little of flow thru a motor.
69VETT

 

Having read all the above posts at least once, some twice, I still think to check the below points in order....

make sure the electric/mechanical fan is pulling air through ALL the radiator core, that it is sealed to the radiator on all 4 edges...and should be a couple inches from the core....

see that the rad is sealed well so the air AT SPEED about say 40 mph... has to go though the rad, not around it.....

then remove the thermostat completely and see what happens...

I have a particular negative towards STANT stats, they have given me nothing but grief over some time now...from outright failures to failure to open on ratings, to just what EVER....including failing to open at all.....lovely....

get a MURRAY stat...and get the type marked fails in the OPEN mode....then to drill 2-3 1/8 holes around the edge of the mounting plate....they run better that way for all sorts of reasons, in SO FLORIDA you not have any issues with MINNESOTA type winter cooling problems, if you DO, we all in deep yogurt....

make sure lower hose is not collapsing under high rpm closing off suction/flow....

the obvious about rad size should apply, but I would think you should get more temp drop across that thing than any silly 8 degrees Fahrenheit...make sure you not reading C there....


I found my little 350 '72 here ran fine on freeways all the time, but getting off and into traffic, it would jump up pretty badly so the addition of dual spals cured that but GOOD....and they are install as per above recommendations...

 

Your top paragraph may be fact, but the second one is still theory and opinion.

 

How did the cold lake water run through the engine? Was it forced in by an external pump or was it pulled in my a belt driven pump?

 

Marine cooling systems that are not a closed loop system are known as fresh water cooling systems and use an external pump to get water such as in the lower unit of an I/O or via a thru hull fitting and a separate pump. The existing engine water pump is still used with a different thermostat housing. The hot coolant is then run thru the exhaust manifolds and expelled back thru the exhaust. Generally a 160 tstat is used for marine.



BTW
Have seen several test results and if memory serves me, the max flow of the coolant thru a radiator tube is 17ft/sec before there are diminishing results. It ends up being all about laminar flow and I believe the next generation of coolers are even named that.

 

Correct. Being a closed loop, the slower the flow in a radiator to dispell heat, the slower the flow in the engine, creating hot spots.
I would look at rad size, air flow, and more importantly, the engine itself. Is it too retarded or lean? It doesn't take much HP to idle.

 

That is not a closed loop system, therefore irrelevant.

 

I would assume that withiut a thermostat, using lake/ocean water you'd be able to chill the engine down to damn near water temperature, and thus damage the engine. I've run engines before with no thermostat (emergency situation, wait for the engine to cool down, take thermostat out, drive home) but NEVER when using an infinite supply of cold water as coolant, like on a boat.

 

That's the biggest bunch of crap I've ever heard.

My brother and I have run 1000+ HP jet boats. Overheating was not your problem. More than likely the first motor never came up to a proper operating temperature causing the failure, and the second motor with the restrictor did come up to temperature.

If I were you, I'd find some new experts.

 

And it is so obvious. Slow moving air doesn't feel as "cold" as fast moving air. It's not that wind chill factor really makes the air colder, but the air has the ability to remove more heat (and thus it "feels" colder) than slow air. Coolant is exactly the same. It WILL feel "cooler" to the insides of the engine.

I don't understand where this Old Wive's Tale comes from, but your analysis on the two boat engines sounds exactly right.

 

dtamustang - is this an automatic tranny?

 

There are a lot of experts here but I do want to point something out that I believe is an error posted by several people. The fans, manual or electric, do not pull air through the radiator they push it. If you put your hand in front of the condenser (headlight side) the air flow should push your hand away (toward the headlights) not suck it in. The fans is for low speed only and rejects heat out the open grill. Once the car is moving the fan is out of the picture.

I had what I thought was a cooling problem and turned out to be a gage and sensor problem. If you can borrow an auto meter gage and sender you may be worrying a whole lot less too. The factory gage and sender in my experience are not linear and "panic" as they get to the top end (190+) end of the travel then slow to return.

 

 

Sorry Mark but that is not correct. The factory fans, as well as properly set up electric fans will pull air in towards the engine through the radiator. The air coming in through the nose while moving is actually going assist the the fan and what it is already pulling through. Having that fan push air out would be counter productive when the car was moving, and consider that pulling cold air from the front is far more effective than pushing hot air through. I really hope you do not have a fan pushing air forward through your radiator.