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mrtexas 06-30-2020 08:23 PM

Electric fans
 

2 Attachment(s)
I know this is not flathead related but lots of hot rod experience here as well. I have a 41 flathead in addition to a hot rod 49. Have a 49 hot rod woody with Ford 302 v8. It came with a 16 inch pusher fan. No room for a crank pulley fan, engine needs to be a couple inches back for that and I don't feel like moving the engine back, modify the firewall, modify steering, cut the driveshaft, new motor mounts, new transmission mounts. When I added AC it started to heat up, maybe overheat. Guy from Walker radiator said Vintage Air condenser blocks air flow too much so bought a Walker condenser that is bigger.

So cruising the web pusher electric fan not near as good as puller? I started the car up yesterday and got the pusher fan running. Sure enough there was a LOT of air hitting my chest even though the fan was pushing thru the radiator. Even removed the DC motor fan to make sure it was turning the right way.

Well the crank pulley is less than an inch from the radiator so not much room for a 16 inch Spal puller fan that is 2 inches thick in the low profile version. So I measured the space for multiple smaller fans. I can fit 3 9 inch fans. Turns out 3 9 inch fans move as much air as a single 16 inch fan. Also amps of 3 9 inch fans 22 anps pretty close to 16 inch fan amps of 21. Will verify the smaller fans fit tomorrow.

So I went to my favorite sheet metal shop and had a fan shroud made up today. I'll put two of the puller fans across the bottom and one fan on the top driver side as in the picture. Have enough room to dodge the serpentine fan belt which is 2 inches from the radiator. Not enough room for 4 nine inch fans either, could put a 7 1/2 inch 4th fan but then 5 more amps.

Some web sites said you need 2500cfm for a v8 but 16 inch fans which seem to be the biggest available only put out 2000cfm. 13# radiator cap. What would max water temp be for that?

What about the passenger side of the fan shroud? Leave it blocked off or put a hole in it to let air flow thru the radiator?

40cpe 06-30-2020 08:46 PM

Re: Electric fans
 

If you cut a fourth hole, I've seen shrouds with flappers over the vent holes that close when the fans are sucking and open when air passes through at speed.

51 MERC-CT 06-30-2020 09:26 PM

Re: Electric fans
 

Quote:

Originally Posted by mrtexas (Post 1904669)

What about the passenger side of the fan shroud? Leave it blocked off or put a hole in it to let air flow thru the radiator?


The three fans will be pulling air thru the fins in unison, suspect that adding a hole will only reduce the efficiency of the three fans by giving a place to pull air from the engine side of the radiator.

JSeery 06-30-2020 09:32 PM

Re: Electric fans
 

Quote:

Originally Posted by mrtexas (Post 1904669)
13# radiator cap. What would max water temp be for that?

Lot of factors, but a rule of thumb is 2-3 degrees for every psi. For a #13 cap, that would be around 26 to 39 degrees. At sea level that would be around 240 to 250 degrees.

mrtexas 06-30-2020 09:47 PM

Re: Electric fans
 

;) good idea
Quote:

Originally Posted by 51 MERC-CT (Post 1904691)
The three fans will be pulling air thru the fins in unison, suspect that adding a hole will only reduce the efficiency of the three fans by giving a place to pull air from the engine side of the radiator.


grumppyoldman 06-30-2020 10:45 PM

Re: Electric fans
 

I have a 16" pusher and 2 9" pullers on my 302 and AC, and have no problems with over heating. Being in a 55 instead of A 41 could be some difference in air flow.

Zeke3 07-01-2020 09:34 AM

Re: Electric fans
 

It sounds like you have a fairly restrictive cooling package if the 16" pusher fan can't push air through it. I do not think blocking the air flow in the upper quadrant of the fan shroud is a good idea. I think it will kill the air flow in that section of the cooling package.

What are the possibilities of moving the cooling package forward to provide room for an engine mounted fan?

19Fordy 07-01-2020 09:57 AM

Re: Electric fans
 

Wouldn't it be best to have as much air flowing thru the radiator as possible for water cooling and also to reduce engine compartment heat?
Looks to me like that 3 hole shroud is blocking a lot of air flow, even with the 3 fans.

Why not run 1/8 in. x 1/2 in. flat steel straps horizontally across the radiator and then mount the fans on them without the sheet metal shroud obstruction.You probably could design the straps in such a way that they could hols all 3 or 4 fans.

Don't t the fans each have their own little shroud? That way you get maximum air flow to and thru the radiator for the fans for cooling your engine and reduces high temps. in your engine compartment. Anything that blocks air flow is not good.

4t8v8 07-01-2020 05:18 PM

Re: Electric fans
 

I put a 302 in a '84 Bronco II. Had the same problem.Solved it by doing some fabrication and moving the radiator forward a couple of inches. Worked great.

woodiewagon46 07-01-2020 05:41 PM

Re: Electric fans
 

Tex, is it possible to move your radiator forward. I know some of the Tri-Five guy's are able move their radiators in front of the radiator support without major modifications. Sorry 4t8, didn't mean to hi-jack your suggestion.

V8COOPMAN 07-01-2020 06:21 PM

Re: Electric fans
 

If you depend on a fan to SUCK air through a radiator, a shroud effectively allows air to be sucked ONLY through the radiator. That's what shrouds are designed to do. Opening a 4th, empty hole in that shroud defeats the effectiveness of the shroud by allowing the fanS to suck air in from the least restrictive area....the big, open hole....RATHER than from through the radiator, which is more restrictive to air flow. This one is not too hard to figure-out. Physics is physics! You can even prove this to yourself by removing the third fan, turn-on the remaining two fans, and feel the suction through the third hole. DD

tubman 07-01-2020 07:09 PM

Re: Electric fans
 

I agree Mr Coopman. There is a guy on the H.A.M.B. ("Hnstray") whose signature is : “In any conflict between Physics and Style, Physics always wins”.

He's right.

40cpe 07-01-2020 08:18 PM

Re: Electric fans
 

1 Attachment(s)
Here is an example of flappers to reduce suction loss at low speeds, yet allow air flow through at higher speeds. Sorry for the small size, I lifted it from the 'net.

19Fordy 07-01-2020 09:09 PM

Re: Electric fans
 

V8; Would it be good to mount a 4th fan over that 4th hole?

50fordcoupeman 07-01-2020 11:12 PM

Re: Electric fans
 

My avatar has a 302 with a 6 blade puller flex fan one inch from the radiator. The radiator sits in front of the air deflector sheet metal (correct terminology?). There is no shroud but the caveat is no AC either. Absolutely no overheating issues. Could you move the radiator forward to get the clearance you need? Good luck

mrtexas 07-01-2020 11:18 PM

Re: Electric fans
 

2 Attachment(s)
Can lower the radiator by a few inches with lots of welding or move radiator in front of air deflector sheet metal but not the AC condenser. Lots of options. Will try the 16" pusher and 2 9 inch pullers. Pusher in front of the radiator and 2 pullers behind. Fan shroud would then only be 10 inches tall and mostly holes for the 2 pullers. Thanks for all the experience and ideas! Have the 16 inch pusher and will order the 2 pullers.

Is best cooling with crank mounted fan?

V8COOPMAN 07-01-2020 11:43 PM

Re: Electric fans
 

Quote:

Originally Posted by mrtexas (Post 1905064)
I'm assuming the sheet metal in front of the radiator is necessary for hood fitment?


Looking at the rounded rise and curvature of that sheet metal panel, as well as the rubber-looking gasket/seal on top of it, and comparing that shape with the curved external body shape of the blue hood below, that assembly seems to be an air dam of sorts when the hood is closed and the inner hood conforms to the top of that dam. This is designed to prevent HOT air that has already passed thru the radiator from being forced back forward OVER the top of that dam, only to be sucked thru the radiator again....at a higher temperature. Same purpose as the flat block-off plates that we '40 Ford guys install horizontally between the top of grill and upper radiator tank.


Seems like a crank-mounted fan would be too low. I would never put a condenser behind the radiator. Doing so would have hot air from radiator trying to remove heat from the condenser. Ambient air should be 80 to 100 degrees below condenser temp on a hot day. DD


https://th.bing.com/th/id/OIP.EqhWJX...r=1.35&pid=1.7

mrtexas 07-01-2020 11:56 PM

Re: Electric fans
 

Quote:

Originally Posted by V8COOPMAN (Post 1905070)

Seems like a crank-mounted fan would be too low.

Crank mounted fan would be near center of radiator. But there is room in front of the deflector only for the radiator and not the condenser. Pusher would be top 16 inches of radiator. Pullers would be in bottom 10 inches of radiator. Radiator is around 24 inches tall.

V8COOPMAN 07-02-2020 12:08 AM

Re: Electric fans
 

Quote:

Originally Posted by mrtexas (Post 1905071)
Crank mounted fan would be near center of radiator. But there is room in front of the deflector only for the radiator and not the condenser. Pusher would be top 16 inches of radiator. Pullers would be in bottom 10 inches of radiator. Radiator is around 24 inches tall.

If crank-mounted fan is above bottom tank, that placement is optimum. Is that radiator clean inside? I'm not sure why you're having a hard time cooling the engine. Whatever you do, don't let temptation situate that condenser behind the radiator. The result will turn-out to be "not cool" (couldn't resist that).

By any chance, is there some sort of abnormal blockage at lower, rear of engine compartment hindering the exhausting of hot air out the bottom, rear of engine compartment? DD

mrtexas 07-02-2020 03:19 PM

Re: Electric fans
 

Just ordered two puller 6 1/2 inch fans. I keep the 16 inch pusher and add the two smaller fans at the bottom of the radiator. Decided to mount the fans with 1 inch straps. Total cfm will be approximately 2,500cfm.


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