Radiator scientists, gurus, and wizards- lets discuss

Well
radiator in this application is down flow
Max overall size is 19x 23
671 with carbs on top - traditional blower set up.
I'm unaware of any bypass of any type for this set up.
Not really an applicable oem muscle car to follow.

There's got to thousands of blown hemis behind 32ish grill shells on the street.
Those are the ones I need or would like to hear about.
Unsure of the amount of 354 chryslers out to 421 cubic inches with blowers but there's probably a few.


( My warmed up 3.8 SC pontiac GTP transplant has a bypass but that's a completely different set up. )

 

To make a complex deal simple. Run the engine in normal conditions and see what happens. If it overheats going slow check the drop across the radiator. If it is less than say 15 degree drop move more air through the radiator. If the drop is 20 degrees but the temp is still going up you might want to slow the coolant down. If it gets hotter the faster you drive I would try to get more airflow with a good fan.. Alloy radiators a really good. This is a black art, your results may vary. Just because a radiator is in the wind does not mean the wind is going through it.
*** I have found that the electric fans found on 70's & 80's or there about Mercedes are about the best you can get and cheap(25 bucks and they never break) if you go to a place like pick a parts. The Mercedes units come with a steel fan, frame and shroud, big electric motor and believe me you DO NOT want to hold one in your hand and hook up the wires to see if it works...and find out it does...kinda have to trust me on that little deal. Those German boys don't screw around when it comes to cooling fans. They beat the heck out of those silly plastic Chinese made things.
There are still plenty of old MB's in the bone yard.
I believe you could hook up one to the front of your car and it would pull you around.

 

X2 what he said

 

Thanks fossil.
I'm a long ways away from driving it.
But my project is completely on hold until I get the blower drive and radiator and cooling fan mocked up and in place. I've been scrounging and saving for these big ticket items for over a year almost 2 with plenty of "emergencies"'that suck the dough out of the piggy bank everytime I get close. Now I'm under very strict orders to procure these parts immediately by those that have provided the emergencies. Blower drive is on the way and the radiator is the next thing.

So I might be really close to firing this thing up in my shop. May even haul it to Tony's for some engine dyno time and tuning. Anybody else besides me want to know how a 421 cubic inch blown hemi runs ?

 

You are all trying to create cooling systems that will only cool adequately at certain rpm's. There is more to creating a system that will be efficient at all stages of use.
There is a fixation on using race styled cooling systems, a much easier system to build as the race motor is going to be running in a very narrow rpm band so the cooling system is simplified.
One major factor that has been ignored is, in a motor that operates through it's rpm/load range constantly varying the water flow speed is also important. The water pump alone is not efficient at varying this as they are made to pump set volumes at each rpm speed, sounds good however this volume has not been tailored to your application. Sure you can get high volume water pumps but again this is a set volume.
Water flow time through the core is important and with a high volume flow water pump you loose cooling efficiency at lower rpms. The answer is a THERMOSTAT!! Yes, that thing you all took out and threw away long ago as one of your first 'hop up' tricks!
I learned much of this from my father, I grew up working in his Radiator shop from the age of about 10 until I left to join the Army, he specialised in custom and performance cooling systems. He owned Bayswater Radiators and FTG Radiators (Norm from Aussie Desert Coolers apprenticed here).

There is still a great deal more to look into for an efficient cooling system, FPI (Fins per inch) in the core, hose size, how far does your water pump have to push all this water, there is so much that it can not be resolved with a simple conversation on the internet. EVERY application is different, EVERY system will have it's own issues. It is not an exact science because of that.
(Yes the physics remain a constant)

The best way to tailor your cooling system is in person with someone who knows this stuff. Learn all you can, pass it on.

Doc.

 

Thermostats are good..have em in all my cars...even the racecars

 

Yea doc, I'm quite fond of them rascals too.

 

I think y'all are overthinking this one with all the science and numbers....

I am neurotic when it comes to properly functioning cooling systems and here is what I do.

Radiator: Brass and copper radiator - I like US Radiators tripleflow Optima - www.usradiator.com. Aluminum radiators do not transfer heat as efficiently. They were built for racing and the street crowd have jumped on the bandwagon on the basis that if it's a racing part it must be good for the street. Wrong. IMO aluminum radiators pretty much suck and Griffin sucks the biggest - cheaply made junk with epoxied tubes. Once the epoxy separates from the tank it's time to throw it in the trash.

Fan: Clutch fans are the best of the mechanical but I prefer to run electric which robs no horsepower. CFM ratings are one of the most widely abused and misrepresented claims of all. Simple rule - if it doesn't draw the amps it cannot pull the cfm. A 35 - 40 amp constant draw fan will pull a freight train. A 14 to 18 amp draw will not pull the skin off a rice pudding! I always use a shroud. I like Cooling Components Inc fans - 2-5/8" deep at the motor yet with a 40 amp continuous draw have all the pulling power you need and are available with shrouds - www.coolingcomponentsinc.us.com . I have just installed two in tight engine bays where nothing else that powerful would fit. Word of caution - use a 70 amp relay or one of their controllers and check your alternator as you may want to upgrade it. If necessary I will use an additional dual pass finned line cooler for added capacity such as the ones sold by Bob Drake - www.bobdrake.com. If you use A/C try and keep some airspace between the condenser and the radiator core. If you are fat fendered, make sure the incoming ram air is channeled through the radiator core and doers not escape around the sides, top or bottom. Shrouds are great but if you use rubber swing flaps to allow the air to pass through and not stall in the shroud, so much the better. make sure you can get the air out of the engine compartment - louvered inner fender panels are a must for good throughflow.

Coolant: I like to use Evans Waterless engine coolant - www.evanscooling.com - which has a 375˚F boiling point and allows you to use an unpressurized radiator cap. It has the added advantage of not attacking aluminum engine components via electrolysis so your exotic aluminum heads do not corrode to nothing!

I also run an overflow tank on every cooling system - reduces those embarrassing green puddles under the car.

One word from the voice of experience on mechanical fans - do NOT use flex fans. They are notorious for cracking at the hub and letting go. After losing three radiators to flex fans I learned my lesson....

 

Good stuff weasel
Thanks

 

I absolutely refuse to run an electric fan. Recommendations?

 

I'm feeling almost as strongly against the electrical fans, they aren't off the table but sure would rather stay away from it.

I've taken great pains to build this to 1962 time frame. I mentioned my project was on hold , we'll that's because the engine isn't in it's final location yet. Not there because of the blower drive, fan, radiator, sorting out and space issues.
That's a big $$$ mock up to make sure it will fit. Might have to slide the engine back. The radiator and or wheelbase might have to get moved forward and hood stretched. So on hold because of my choice against an efan .

There's only so much room and you can pick your battles and compromises.
If your last thing to work out is a fan , it will be electric due to space issues.

 

Your problem is obvious, the radiator is on backwards. This is a great thread. <?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o>
And also, blowers make A LOT of heat? Richard D<o></o>
Blowers generate their own heat that effects the air fuel charge.I would think that at 70 mph the natural Cfm flow would far exceed the 2600 to 3000 Cfm of an electric fan.
Secondly blowers should be increasing net HP and that needs to be handled by the cooling system. 31Vicky with a hemi<o></o>
To address the comments above, Blowers generate heat when they compress air. Air heats when compressed, can’t violate that law of physics. The tradeoff is that you can make more HP because more air+fuel is being artificially crammed into the combustion chamber. That’s why you see intercoolers downstream of turbochargers. Their packaging is easier than a Roots type blower. Internal combustion engines as we play with them are horribly inefficient as has been pointed out.<o></o>
As far as natural airflow available at, lets say 60mph (5280ft/min) to make the math easy. A radiator 18 x 24 inches is 1.5ftx2ftx5280ft/min = 15840 cfm UNRESTRICTED airflow available.<o></o>

 

See 15,840 is a hell of a lot more than 3000!!!
How the hell can these guys rate a radiator the way they do and up the rating because they upped the Cfm by 400.

That's one of the main questions in this thread

 

Clutch fan. If you run a fixed fan, no flex fan blades - the stainless riveted to a steel center type - as I mentioned in my long winded post....

 

What about fan shrouds ideas, and thermostats, when using mechanical specifically?

 

Quote; treb11 (Your problem is obvious, the radiator is on backwards. ) Dang,,, glad you pointed that out. All this time I've been trying to find a pair of Molded Rubber Hoses to go around the corners. And I thought I knew it All. L.O.L.
The Wizzard

 

Yep, shrouds are a great help and, as I mentioned before, if you have a separate grille make sure all the incoming air is channeled through the radiator core and not around it and louvers on the inner fender panels on fat fendered cars will help get rid of the hot air under the hood. You can still use line coolers and Evans Waterless Coolant with mechanical fans. using a separate trans cooler for automatic trans rather than having it built in to the radiator also helps reduce the thermal load on the radiator. Use a thermostat with a 1/8" hole drilled in it as a bleed hole to prevent air or vapor lock. I like to use a 180 Robert Shaw like this which already has the hole drilled....


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If you are making too much heat then maybe you need to do something like this.
Engine fans need to be fixed pitch steel blades, I like heavy duty fan clutches too. I do not mind the fan noise if I know cooling will be right.
On my racecars I like a 17 to 21 pound cap. Expansion tanks are good and keep the coolant in the system not on the ground. I use distilled water.
On the dirt track and circle track cars I have built I always made the shrouds. With a rigid mounted engine you can get the fan blades to almost touch the edge of the shroud.
I found that after doing this I never needed a forward facing radiator opening again. I closed off the front and the fan pulled air up to the radiator from the chin of the car..no more crap in the radiator.
I would come off the track and the engine would get hotter idling in..park the car bring the rpms(no real load so it was not making the heat it made on the track under load) back up for a short time and the engine would cool then I would turn it off.
If you do the shroud correctly you will see it suck in due to the negative pressure when the throttle comes up.
Just make sure that 25 to 30 percent of the fan blade is in the shroud and the rest is out side to sling the air out. If you stick the fan all the way in a shroud you now have a blender not a fan.
If you can't do the shroud thing than put the fan as close as you can to the radiator, bout 1/2 inch or so..watch for flex and engine movement too.
Your results may vary.

 

I'm putting a V-8 in the front of a '62 Corvair. It has no grille; I was planning on holesawing it, but now maybe I'll try sucking air underneath? Making a shroud will be no problem.

 

Of all the things you can do to improve low speed cooling , a propper shroud is by far the most beneficial

 

Going back to your original post, I think I might be able to offer a little bit of an explanation to the HP/cooling rating thing.

Everyone is right, in that there are many, many variables to consider, but the radiator manufacturers need some way rate, market and sell their product.

The coolant takes heat from the engine, and the air going through the radiator takes heat from the coolant, and transfers it to the air. Additionally, typical gasoline engine will require certain modifications and displacment to produce a number like 600HP. The power output is determined by variables such as mass flow rate through the engine (fuel and air), displacement volume, and change in temperature of the fuel/air charge before and after combustion. I'm guessing the radiator guys are assuming a certain intake temp and combustion temp based on gasoline along with "typical" compression ratios and "typical" displacements to generate 600HP.

Based on this "typical" 600HP engine generating a predetermined heat load, the radiator guys say it takes a size X radiator with a 2600 cfm fan, to continue removing enough heat from the coolant, so that the cycle can continue. I'm betting the fan rating is based on sitting still with all the air flow being generated by the fan, and not induced by driving and forcing more air through the radiator.

Based on the assuptions above, a typical 700HP engine creates a higher heat load. That extra heat load could come from a higher compression ratio or a blower, etc... Therefore, it takes more cfm to remove enough heat from the coolant to continue the cooling cycle.

So, I don't think the radiator is actually cooling a 600HP engine AT FULL LOAD with just 2600 cfm. It's just their way of marketing a radiator that will cool a typical 600HP engine under typical operating conditions. I doubt any of this will get you any closer to selecting a radiator, but maybe the rating makes a little more sense.

 

I agree with "Weasel" do not use a flex fan I had one fail on my car. Don't get caught up in the aluminum vs. copper stuff. Both are good but my cars have copper and I am very happy with them. As far as cooling your car perhaps just as important as radiator size is a good radiator shroud to direct all the air thru the rad. I live on Long Island and my deuce roadster ran great except when I got stuck in traffic trying to get off the Island. When I built my car I cheaped out and didn't install a shroud and I finally broke down and installed one and now I can sit in traffic for hours at 180 degrees. The latest issue of Street Rodder has an article about cooling.

 

Up for more

 

Thanks willys rule -

I suppose that they need "something" and I'd also suppose its not ever going to be a "something" that always makes sense. So I've come to the realization that their rating is based on marketing and sales and probably multifit inventory or manufacturing not necessarily helping a guy choose a radiator. I suppose that if they had a 5000 CFM fan the rating would go up again??? This thought brought the second question of how much air does the mechanical 7 blade fan move ?

With the radiator being the constant...

The Cfm of a fan is most important at slow speeds and minimal air against the radiator like traffic and lights etc. Also this exactly the times when HP is the lowest. The radiator needs to shed some heat in this situation.

The cooling ability (heat transfer) of the radiator is most important at higher RPMs when HP ( heat) is the highest being generated by the engine. At full load the radiator needs to shed ALL of the heat.

 

Didn't read the whole thread, but I hope this will help...
I did a little research and some number crunching and came up with:
30% thermal loss X BSFC X BTU/lb of gasoline and ended up with a figure of
50.4 BTU/min/hp produced as heat lost to the cooling system in a typical gasoline engine. So if the engine is making 25 hp sitting against the converter in traffic, you'd need to exchange 1260 BTU/min to passing air.

Not sure how that would equate to fan CFM, sorry.

 

Hell man, don't be sorry for that!!!
That's Beautiful

 

It's not a simple set of formulas. Start by reading through the attached PDF document....

 

I might be way off here.If I am,just fire up the flamethrowers.Hehehe.
I noticed that some of the guys said to leave about half to 2/3 of the fan blade out of the shroud.
HOWEVER.In the aircraft industry they use ducted propellers to not only quiet the sound of the AC,but they found that by doing so they increased the efficiency of the prop.Most of the noise of an AC IS prop tip scatter caused by the prop tips breaking the sound barrier.By having the duct ID within IIRC 4 inches of the OD of the prop that kills the tip scatter,thus quieting the prop sound.So,if that works for an AC prop,why would it not work for the cooling system fan for a car?Altho,you STILL have to get the hot air from under the hood.
Good luck.Have fun.Be safe
Leo

 

In ducted fans the housings are really big venturis. The design of a ducted fan is to provide thrust. What you say would work too but the venturi is pretty long and is not needed to push the car down the road. The fan on a car is there to pump air not create thrust...it works better to allow the air to sling out as quickly as possible once it leaves the low pressure area/shroud. Different required results require different designs.
"it is all my fault and don't you forget it"

 

Hi Fossilfish.Thanks for the reply.
Good luck.Have fun.Be safe.
Leo