Radiator scientists, gurus, and wizards- lets discuss

Fossil Fish hit the nail on the head with the problem I experienced with a 440 in a 71 Demon. I had the three core big Chrysler radiator, large clutch fan with shroud and it still would boil in the drive up. I blocked the water bypass hole in the pump housing, cut holes in the inner fenders etc. The solution ended up being a 195 degree t-stat. The water was moving too quickly with the cooler rated T-stat to disapate enough heat. One the water was slowed down in a cyclic rate I never had a heating issue again.

 

To each his own, but I don't think coolant can go "too fast" in a heat exchange system. (Assuming you keep it sub-light, you know. )

Analogy:
If you had to travel through a refrigerated warehouse that was about a hundred yards long, would you walk fast or slow? And why?

Now extrapolate that walk to the coolant's "walk" through the radiator. And I think things will become clear.

Consider these points that offer some explanation to the anecdotal evidence seen here and in many other threads.
http://www.flowkoolerwaterpumps.com/cooling_faq.html

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The points raised here about mysterious overheating when it "shouldn't" are valid. I think the trouble is that many of these installations have modified the things around the radiator and the engine in such a way that the air doesn't flow as it should. Most modern cars are designed so that, at speed, the fan cuts out. What makes the air flow through the radiator is a slight negative pressure created behind and below the radiator as the car pushes through the air. Now for that to work, the radiator itself must be the easiest way for air to flow in and fill that slight vacuum. Unfortunately, things like cowl hoods, holes in fenders, etc. can actually work completely against that goal. They may help when the car is sitting still and hinder when moving!

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I thought more about the blower and realized that there's probably no period-correct bypass setup for a 6-71. Considering that they came on diesels, they would not have needed one. There's no throttle plate for them to suck against. Unfortunately, that means the blower will build up heat while just idling.

You could fabricate a working bypass, but I think you would have to make a special adapter plate for the top of the blower and place the carbs under the blower to avoid fueling problems (double-fueling the air and overly rich mixture at idle and cruise). Probably not what you want on your 1962 rod.

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In your specific situation, you have a maximum size for the radiator. If that's a hard constraint, you will have to work with it. I would max out your available dimensions. Consider that 18x24 is a fairly common size, so you may want to see if that can fit. And your water pump and thermostat should probably be stock pieces. The only questions left in the mechanical design are how many rows and what fan? Consider that those two factors can work against each other. The more rows you have, the harder it is to pull air through them. And the effectiveness of the rear rows will drop off because the temperature difference between the air and the coolant will be less as the air moves back and heats up. A typical car would have 2 rows, I believe. You may want a little more cooling than that. So why not try a 3-row and work from there?

Also consider "waterless" coolant or "water wetter" that can give you a little cooling boost.

 

Thanks Mazza!
I was thinking about the number of rows and the added air restriction.
The FPI count provides the majority of restriction and these contact points provide the heat transfer.

For the sake of discussion, what would be more effective at cooling ?
A 2 row with 14 FPI or a 4 row with 7 FPI? (Tube size and count being equal for this. The restriction to airflow should be much less on the latter and pass more air. Maybe it would be a wash on cooling ability because the contact point count would be the same and only be a bigger package ??
I ask because I did find a supplier of cores that has almost what ever configuration you could want.

 

I've been battling these issues forever, I love big blocks with blowers. A '53 Studebaker has very limited radiator space, and blower drive systems eat up fan space, so I've built a car that needs every trick in the book to sit at a traffic light. I still can't reliably drive this thing in traffic, so I still have work to do.

 

WHAT??!!
The idea is that the coolant picks up heat FROM the engine.

In your analogy, why would you run through the warehouse if you WANTED to get cold???

 

Well I'd run because I wouldn't want to get cold.
The energy I was creating would keep me warmer and I'd shed less heat if I was in there less time.

I'd want water in an engine block to have close contact to the surface area and move slow enough to pick up heat. Then in the radiator, close contact to the surface area and enough surface area to shed more heat that its picking up in the engine.

If the heat generated matched exactly the heat being shed (100%/100%) then the system could operate continuously. Although it be dangerously close to failing if something changed the slightest bit. All you need is just enough but this is living on the edge.

If the heat generated exceeded the heat being shed by even 1% ( 100%/99%) then the system would eventually overheat.

 

Vicky,
That's why the engine heats up and cools back down, right? (Theoretically) we only need max cooling at max heat output (power). Under any other circumstances, we are back away from "the edge" and able to cool the engine back down, IF we have a correct state of tune and adequate airflow through the radiator. Since many engines heat up coolant under almost NO load (idling in traffic), that means the slower coolant flow is picking up more heat from the metal, which isn't a bad thing IF we can keep getting rid of it.

IMO, as long as the system isn't puking coolant out, don't worry about 210-220 deg at idle. If there is enough airflow to keep it there, that won't hurt a thing.

 

I don't want to get cold! Springtime is finally here and I want to enjoy it!

I didn't explain myself well. What I was getting at is that heat transfer takes place over time. So the longer you spend in that freezer, the colder you will feel. That's why we would all hustle through it.

I think some people visualize the cooling system to that point and then stop. The thought process is something like, "The coolant has to spend a certain amount of time in there or it won't get cold enough, and the engine will overheat." But they overlook the fact that it's a closed system ... and for every drop of coolant moseying through the radiator getting nice and cool, there is a corresponding drop of coolant moseying through the engine, picking up too much heat, and boiling!

Therefore, you want "enough" coolant flowing through the engine and the radiator per unit of time to shed the heat produced by the engine per unit of time. It's mostly about mass flow rate. And, of course, you need enough mass of air flowing across the radiator to take the heat from that coolant. It has to be enough to let the engine run at the desired temperature without overheating.

This is what I was getting at before. Sorry if I confused anyone.

 

I've been reading up on the waterless coolant.
This is pretty interesting stuff and still trying to get my head around it.
But basically the dreaded 220 zone really doesn't apply because the stuff doesn't boil until well into the mid 300 zone. The 250/260 zone is flash boiling the water in the cooling system and creating vapors that can't cool because there's zero surface contact and zero cooling. That starts the More boiling more vapor less cooling spiral until the thing melts from uncontrolled temps probably pushing 1000s of degrees. If you push off the flash boil point for another 100 degrees that really extends the legs of the cooling system.

I don't know what temps the internals can handle if the cooling jackets get up to 320 without boiling, mainly because its been boiling at 250.
Interesting to think about

 

Too much damn 'rocket surgery' going on here about thermal dynamics. It's not about the semantics and the hows and whys but just about getting an efficient cooling system that works. Airflow, triple pass radiator such as the US Radiator optima core shroud and Evans waterless coolant should get you there. Boiling point of 375˚F, running an unpressurized cooling system and no corrosion from electrolysis all make it a must in my book. Invest the money in your cooling system and eliminate the problem....

 

I don't know about too much, but I was completly unaware of "waterless coolant " until this thread.

 

I agree with your conclusions, Weasel, but re-read the thread title. It wasn't "HEY, give me a canned cooling system solution without teaching me anything"...

BTW, I did quite a bit of research years ago into cooling systems on automotive power plants for use as stationary engines. What I found was pretty amazing. Most all automotive water pumps are most efficient at 3000-3600 shaft rpm. That's why trucks, generators and pump engines all overdrive the water pump from the crank. A high rpm racing engine will UNDER drive the pump as much as 50%.

If all you are doing with your "traditional hot rod" is cruising the fairgrounds and running the freeway in high gear, spin that pump up faster... The thermostat will still restrict the max flow, but the pump will build more block pressure at lower engine rpm; which in turn transfers heat better and helps eliminate those steam pockets.

 

I had a 70 F'lane 302 and back in the gas crunch 70's I was messing around for better gas milage, what I found..
1) Thermostat...As previous poster suggested, good quality [$$] like Robert Shaw at around $20.00...Your common low cost are not that consistant in the quality department and will deviate pretty quick..If you suspend one in water on a stove and heat the water up you will see that the thermostat opens very quickly, if I remember it was as little as 10° from closed to full open..Just because an engine is idling with a 180° stat and staying at 180° doesn't mean the stat is full open..Cold/Hot weather the therm is the water flow limiter, regardless of fan speed/engine rpm or load..

2) Radiator..Has to be able to cool the most water flow at the highest temp entering by enough so the themostat can regulate, at idling and high rpm..Measuring in and out radiator temps can be interesting....A 160° therm the engine ran at 165°, 180° was 185°, and 195 was 200°...BUT the water always exited the radiator at 140°!! Wether ambient temp was 20° or 90°, idling or 55mph....

3) Fan...Must be of enough capacity to cool whatever temp/flow rate or engine rpm the water inters enough so the therm can regulate, i.e. the above mentioned 140°..

4) Figure that 1, 2, and 3 have to service each other, catch 22....

5) a. Always use a thermostat..period..
b. Use a healthy radiator but be prepared to have to block it off some [or alot] in cold weather..
c. Fan is really a culpret to me, too much and cold weather is a problem and too little idling is problem..variable pitch mechanical would be nice..

6) In one of my cars [with AC] I run a healthy 4 row copper radiator, healthy 6 blade alum fan from 61 buick and block half the radiator off for weather colder than 50°...

 

In my race cars, I run High Compression, and no power adders. I use an aluminum radiator. The biggest I can fit. Compression /HP makes heat

It is simple, The radiator has to be big enough to cool the coolant faster then the engine can heat it... at a specific flow...

Air passing through it plays into the cooling. Flate tubes allow more surface for the air to pass over....

The radiator has to have the capacity to cool faster then the engine can heat coolant.

 

Coincidence, I was doing mileage work on a '69 Mustang with a 302, what did you get with your's? I know, off-topic, I'll make up for it.

 

""Coincidence, I was doing mileage work on a '69 Mustang with a 302, what did you get with your's? I know, off-topic, I'll make up for it.""

Man that was a long time ago but the first thing that popped into mind was maybe like 14/15 around town summer, 13/14 winter..Never ran enough highway to check there..Rear gear was 3.00 and c4 trans..Car weight was 3660...After running a 65 Comet with 200 6L, 4spd, 3.20 gear and 2750# I was spoiled...