The Stovebolt Site Forums The Shop Area Engine Shop Electric fan CFM ? ....updating the entire cooling system

My 49 Half Ton has been overheating all summer. Have replaced the radiator, water pump and thermostat but have not yet run it yet. Am going with an elec cooling fan but only have room for 12" or smaller

What CFM will I need to keep things down about 185 or so in 95+ summer weather? We are also flushing the block just to be sure all bases are covered.

Just looking at an elec fan online catalog I had no idea they drew so much current ! I may well decide to move the battery up front as well so I can run a larger one..

To run a larger fan, pull battery power right off the starter with heavy wires to the fan, use a relay to trigger it on and off. Might save you from moving the battery.

A 12" might not be enough fan, it will only pull air from a 12" diameter of the radiator unless you mount it out away from the core and use a shroud. This will let the fan use the whole core.

Mechanical fans will out perform a electric every time, a mechanical fan with a clutch will work even better. I would use electric as a last resort.

Always use a thermostat, they not only control warm up but also water flow rate.

Tune up plays a major role in engine heat, timing needs to right along with fuel mixture.

Joe

I'm pretty sure that won't be the answer, the regular old fans have been quite successful for nearly a 100 years. And in the case of your very vehicle, about 60 years. You have other issues.

We have used a short shaft water pump but still not much room for a reg'lar fan. Even a 16" elec fan won't fit in there. Must say I'm disappointed to hear they don't work all that well... Chose not to used the water pump re-location plate because of the necessary extra holes needed to stabilize the plate/pump... so we're stuck with little room. The 'old' rad was actually from a 41-46 car and water pump was beginning to seize up. Thermostat was also sticking... New rad is much bigger and intended for a truck...

Will assemble all we can and report back...

What year/ size engine are you running?

1957 235 from a car..

What do you find wrong with drilling the two holes for the plate?
It is very simple and would cure your problems, and you have the plate.

Be cool might have one for your application. I run an electric on my 65 c-10 with factory radiator. It cools my blown 383 just fine. Temp stays around 185. The website list quite a few styles. Perma cool has a 12.5"x12.5"x3.75" that pulls 3300cfm. Listed for $170.00 in my summit catalog.

Was not me that nixed it...it was my mechanic who found it flakey and likely to drill into a water line of some sort... I just follow his advice...

So this thread does beg the question - how do you know what cfm a particular fan will move? Is there a formula for obtaining such a number?
I haven't seen a fan made that has that information anywhere on the fan.

Joe, I've checked lots of fans in stock at Advance Auto. "MOST" all of them list the part number/width and CFM. Of coarse the info is on the box and not on the fan.

I didn't have much room in my panel running the serpentine system so I used a sensor from Speedway and my neighbor gave me an electric fan off his blown 383 and it does a good job.

Dogface, you can put a "pusher" fan on it but I'm not sure how well they work. I did not like the pusher I once used on my '37.
I don't have much room in the 37 to run over a 14" fan so I'm going to a thin 16" electric that will cover the entire radiator and keep it cool in parades.

....maybe something I said will help someone??

I just went by the advertisement. Check out PERMA COOL. They claim 2x cfm of other fans the same size and are ideal for engine swaps. They list all measurements and cfm.

At least one site I have bk marked gives that info for SPAL elec fans...

www.a1electric.com/catalog/cat_spal.htm

Thanks, amigo....I have heard that pusher fans are not all that good too.

Try moving the radiator forward, I relocated the side mounts and moved mine forward about a 1". That was all I needed for a 17" heavy flex fan.

Joe

My thought too, Joe. I was under the (mistaken) impression that electric fans did a good job. ?

Electric fans work great, especially when you don't have room for a mechanical fan. The best rule of thumb for CFM is just to put in the highest CFM electric fan you can fit. Try places like Flex-a-lite, they have the dimensions listed on their website as well as CFM.

It all depends on the shroud and how much of the core the fan can pull air through or push through. No fan will work very good if it only moves air through a portion of the radiator core. The electric fans that really work good, pull a lot of amps and pull air through the whole core. F*rd used a very good fan on the Crown Vic's, if you can find one in the pick & pull, you could save some money. I believe these are the dual speed fans. Be sure to compare amps and cfm, then decide if your charging system is up to the extra task.

For a while I used a Flex-a-lite 17" fan with the flat front and even bent narrow fan blades. It fit the tight location but moved very little air. After moving the radiator forward, I was able to switch to 17" curved, much bigger, blade fan which moves a ton more air. Even with the radiator 10" from the grill, I can still feel the air moving when at a fast idle.

I do agree with 46gmc, go as big as possible with the maximum cfm offered if you choose to go this way.

Joe

using an electric fan in the pusher orientation, can actually impede air flow at highway speeds, As far as drilling the holes, as Dave has suggested. I would listen to Dave, he has a whole lot more experience with these engines than YOUR mechanic I am almost certain of that. Unless you have changed something about your truck dramatically, (replaced the six with a blown hemi or something) The original setup works very well with a large margin of extra capacity. I ran mine with a 195 degree thermostat for 25 years, it didn't matter what the outside temp was, it never wavered, I live in Seattle now, but the truck was originally in San Diego, where I drove it for 3 years. It isn't the hottest part of the country, but the cooling was never even an issue. Not even on the trip through death valley with a GVW of 5400 LBS, (it was loaded) I would at least check it with all the new pieces before I went and started removing extremely proven components.

I would go pull style. That's what I run and have never had an issue. I also run the purple Ice additive. I don't know if it helps at all but the label sounded good.

Seconded. No offense intended, but it sounds like your mechanic isn't familiar with the Chevrolet 235.

That is pretty much true...he's a young guy but works with his Dad who is my age and a good wrench in his own right. I'm sorry to offend anyone, especially Dave.. They, having NEVER done this procedure, were worried about hitting a water jacket line and didn't like that the plate does not fit flat on the face of the block. I have to go with what they say... sorry... I have zero experience of my own on this stuff...

I can assure you I am not offended. I am disappointed. I like to help people out and I know how well this setup would work for you. I have been installing these adapter plates for close to 20 years and have had 100 percent success with them. I wish you the best of luck with what ever setup you decide to use.

Thanks Dave...who knows... I may be back to it eventually... I do know you are the go to source for those who can do it themselves...which is most people here...but not me. I been cuttin' on cats and dogs all my adult life and they heal over my mistakes themselves... <smile>....not so with iron and steel...

So...to continue irritatine you all.... <just kidding> here's a pic of the fan and shroud. The shroud is a full back side cover so the fan has to pull thru the entire radiator... Block flush is next then back together for testing... Still hot enough here...maybe 96...to get a good test. The relay is settable to any temp you choose.

http://s1276.photobucket.com/user/Dusty411/media/Radfan_zpscb7c53b6.jpg.html

most electric fans really are not what they are advertized. only two companies that I have ever tested make close to the CFM that they advertize. that is Spal and Tri-Pac. The most CFM is the Spal fan used by Nascar. it flows 2900 CFM of air at 0", or about 2200 cfm at 1.5". which is pitiful as the standard engine fan will push much much more.

to get true fan CFM in your cooling system, you need to know the pressure drop across your radiator core. in most cases, its 1.4" - 1.7" Then you need to get the full fan curves from the vendor and then you can get the actual fan flow for your application. Pusher vs puller almost no difference in performance and I have the dyno runs to prove it.

the key "rules of thumb" for any fan installation are as follows:

Fan IS to be shrouded (this is the biggest improvement to fan efficiency). Did I mention that the fan should be shrouded.
Fan tip to shroud clearance is to be as minimal as can be (to minimize fan re-circulation known as tip loss)
Fan face is to be a minimum of 1/2 the hub diameter of the fan away from the core (this minimizes the useful radiator core blocked by the fan hub)
Your fan is not needed above 25mph, as the velocity of the air from driving exceeds that of the fan.
Fans require horsepower to run.

that being stated. My recommendation is stay with an engine driven fan. if you still overheat, look at the radiator and engine coolant flow.

Thanks for all that info. It took a lot of your time to in put all of that!

The fan just installed is a SPAL pulling 2k or so of CFM. The radiator is new copper/brass. Water pump, thermostat also new. Block is being flushed tomorrow. A full shroud was made so the fan pulls from the entire core. Not sure of the measurements you listed. I'm pretty confident it will all come out well.

The old rad was way under sized and obstructed. The water pump was binding and the T,stat was sticking shut often.