Steve; Just curious- How far are your fan blades from the radiator, and do they protrude from the fan shroud, and if so, how much ? /Duck

BOO- YA!!!

Hi Duck - Tthe fan blade leading edge is 3-7/8 from the radiator and it sticks out the back of the shroud by 1/8 or less. The T-bird shroud has a sort of "spherical" shape at the rear 2-1/2 inches or so and I configured the cut down Pontiac fan to have a leading edge that just neatly sweeps the space (with reasonable clearance).

The fan came with a junk GM clutch I had to throw away.......

 
 Steve Metzger       Tucson, Arizona

Just a couple observations.



I was motoring along one evening, cold in December, in a vette on cruise control about 2800rpm. Suddenly, the car lost about 5mph, roared like a jet was making a low pass, and the cruise kicked in and added throttle. I tapped off the cruise, slowed down and pulled over. Everything seemed normal. Got out, opened the hood, and seemed to have a bit more fan noise. I shut the motor off, grabbed the fan, and the thermal clutch was frozen up. Obviously failed at speed. But it made it clear to me how well they worked. I left it on that car all the way thru 400hp, with air and power everything, and a big block radiator, and it ran about 10 degrees warm on a 95 degree day. Way better than any flex fan than I ever had.



I've been running an electric on the 'bird since I put the s/c on, and am about to put an aluminum radiator in it. I was going to build a shroud, but based on Steve's input, I'll be checking to see if I can go that route with the s/c off.



An old time motor home and truck guy told me if I could find a 25hp electric fan, it might keep me cool on a hill in the motor home. That kind of tells the story.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

Is this a case of "Mission Creep"?

This started out because a factory medal fan at high engine RPM pulled the waterpump shaft forward and took out the radiator.

Now we are talking about how to keep a motorhome cool as we climb the Rockies and what happened to a Corvette when the fan clutch siezed.

If you have a high RPM engine and want to reduce the force on the waterpump bearings start by reducing the mass ( weight ) that is on the waterpump shaft. NO FAN-CLUTCH, NO IRON FAN. Look at a fixed aluminum multi-blade fan or a flex fan.

If cooling with a fan shroud is not an issue why try to solve a problem that does not exist.

OK I feel better. Pete

Sorry, Pete, your probably right.  My point was they take a lot of power, and that means a lot of load one way or another.  I never realized how much until I had those experiences.

Glad you feel better. We can all use a little of that.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

Philo:



Many of the water pump re-builders today are re-using the impeller and hub and gluing them down with epoxy or other loctites. I refused delivery of a pump a short time ago that had a used impeller and hub glued onto the shaft. I bought a new pump instead for just a few dollars more.



When we used to buy the kits to rebuild the pumps ourselves it was a definite no-no to reuse either the hub or the impeller because when you pushed these items off the shaft you would remove a thousandth or micro-thousandth of metal. The hubs and impeller are cast so are softer than the steel shaft. Removal of this small amounts of metal would allow looseness and sometimes allow the impeller or hub to shift on the shaft.



To use the truck water pump you should check the impeller to casing clearance as the trucks use a different timing cover than the sedans.



I agree with Steve on the flex fans they are more hype than help.



Ford used a 5 blade 18" fan as an optional extra cooling fan on the Ford and t birds and a 5 blade 18.25 fan on mercs.



I would look for a 5 blade fan and a smaller water pump pulley if you have a engine temperature problem. I run a 5 blade fan with a water pump pulley off a 57 merc with HD generater as these are smaller diameter than the 56 and later pulleys are.



marv

Marv,

I wrote a long winded reply to your informative post this morning, but for some reason it didn't post..............The bottom line was; Where did you get the new pump you trusted and/or what brand was it?

Thanks!

Philo 

FIGHT CONFORMITY! 

The water pump is made by Elgin. I bought it off ebay from one of the supplier. Cost about $80.00

Here is one

item 220773721563

marv

Nah. I do think he's trying to illustrate why an electric fan might not be the best choice in every case.....



I had the same questions when I was selecting the fan for my 292......it's going in a truck (a REAL truck) not a 1/2 ton car that will never tow or carry anything...... so when I work the engine I want enough airflow to keep everything cool. Electric fans are great for most of the vehicles out there cruising along on level ground......



Go try to buy an electric fan system to replace the engine driven fans on a motor home though (or any F-250/350/etc truck that will tow something BIG) and the electric fans required to do the job become VERY expensive and they draw upwards of 50-100 AMPS to make enough power to run the motors....to move the air!



Just consider if your engine driven fan needs 1-2hp HP to turn it at 3500 (towing RPM) that's



around 750-1500 WATTS. At 14V that would be around 50 to a little over 100A (possibly exceeding your ALT output!! )



This is why I am staying with the "high-mount" fan on my F-600 and using a clutch.













yeah.....go for it but you'll need a trailer to bring your big 20kw generator along!!.....a 25hp 12v DC motor would need an alternator capable of supplying more than 1500 AMPS !! Otherwise you'd need to power a 240v motor for the fan!!



I suppose 25hp for the fan is a bit of an exaggeration.......






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1955 F-600/272/E4OD// Disclaimer: No animals were injured while test driving my F-600 except the ones I ran over intentionally!

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This post was created using OpenSuSE Linux x64 and Firefox

I'm not understanding why electric fans are worse for towing. First off, many electric fans have more efficient blade designs than engine driven fans. This means that the electric fan can move more air for a given power draw which makes it difficult to compare electric and engine driven fans directly. Electric or mechanical, it simply has to move enough of a volume of air in order to cool the engine sufficiently; the means of moving that volume should not matter.

Now, looking on Summit, I picked a fan, a flex a lite 398. It is a 16" that moves 2500cfm and draws 17 amps.

Since fans are round, we can assume that the volume that will pass through can be represented by a cylinder. The formula to calculate the volume of a cylinder is Pi x r squared x height. Pi x r squared is 1.396 feet. We know this fan moves 2500cfm in one minute so height must be 1790.493ft. This means that the fan moves a column of air 1790.793 feet long in one minute. That is equal to .339 miles in one minute and since there are 60 minutes in an hour, that equals a velocity of 20.347 mph. So in this instance, this fan will be worthless above about 20mph. In reality it will be a slower speed that the fan is no longer required because the area of the radiator core will be much greater. If we use my trucks radiator, which is 26" x18" or 3.25 square feet, it works out to 5819.103 cfm of airflow across the core at just over 20mph.

Another, Flex-a-lite 180 moves 3300cfm with a 15" blade and 18 amp draw. That's equivalent to traveling 30mph or 8580cfm across the core at that vehicle speed. Just how much air flow do you need?

So if airflow is what is required to cool an engine, how is it that an equally sized, more efficiently designed electric fan is no good for towing? I personally have no experience with towing so there could be a variable I'm not considering but it isn't adding up. In fact, one of my friends has a Chevy 1500 with the towing package and it has factory electric fans.


Lawrenceville, GA