Technical Small electric fans vs engine fan and shroud

I have a 37 Chevy customized sedan with a Chevy 350 with AC and a 700r4 that runs very hot in parades. Originally, I was going to use an electric fan with a complete shroud but didn’t have enough clearance between the fan and the water pump pulley. I installed a Flex-a-lite 1817 Blue Star Stainless Steel 7-Blade 17" Fan and didn’t have a shroud and didn’t want to take time to make one as a friend and I were assembling the car after paint.

The radiator is an aluminum Griffin designed for the 37 and the radiator itself is 16 1/8” X 22 ¼”. The car doesn’t run hot in normal traffic or on the highway but got up to 230F during a 4th of July parade. Since I don’t have a shroud the upper third of the radiator doesn’t have air moving through it when you’re idling along at 1-2 mph.

I had decided to make a shroud but it was suggested that mounting 4 6” fans would be better than the engine fan with a shroud. Access to the radiator area is difficult and, in some respects, mounting the 4 fans looks to be harder than making the shroud. I have no real access to the front of the radiator without breaking the AC loose and removing the doghouse and I want to avoid doing that.


Any advice on running small electric fans versus a 17” SS flex fan with a shroud? Thank for any advice! Tony

 

My car gets up to 230 on hot days, when it gets up to 240 I find a place to pull off the road and let it cool down a bit.

You might or might not have to do something about it. If the car never boils over, then you're probably OK.

 

I can't tell for sure from the picture you provided but it looks like the fan is not centered in the radiator. It looks low. My error?

230 isn't that hot, considering parade traffic. Did it belch or just a hot gauge?

I would try the fan shroud before going to twin electric fans.

 

A shroud is absolutely the best solution........ IF the cooling is inadequate. It should be tailored to clear the blade tips by at least a half inch. (You may need a little more clearance if your engine "torques" or move a lot.) This results in every square inch of the radiator dumping heat into the airflow.
I'm not saying that the hodgepodge of small electric fans wouldn't work. But that's like using 4 bandaids on a booboo when one big one will do the job. A typical situation in which multiple fans are needed is when a radiator is extra wide and not very tall. Then 2 or more in a row might make sense.

 

A mechanical fan with a proper shroud will move more air than any electric. Another thing to consider is what happens to the hot air after passing through the fan. You mentioned parades, so slow movement or sitting still. The hot air will recirculate over and under the radiator, or under the car and back through the grill. Seal the radiator to the grill shell and a bit of belly pan/duct to send the hot air rearward.

 

If you want to stick with the mechanical fan, definitely add a proper shroud to the equation, it will make a huge difference. As it sits now, at idle that fan is just blowing hot air around the engine compartment.

The recommendation for multiple small fans is wrong. If you don't believe me, spend a couple minutes looking around at all the radiator manufacturers and their fan setups, you won't find a single one with a bunch of small fans. A pair of fans, yes, but not a bunch of 6-inchers.

If you want to go with an electric fan setup, get the largest diameter fan you can find and make sure it comes with a shroud. Avoid mounting it via zip ties or those cheesy plastic "through-the-radiator-core" things. Check out Derale or someone like that for a good setup.

One more thing, avoid adding a pusher fan to the front of your radiator as it will likely cause more trouble than it will solve. They tend to block more air than they move.

 

I had a 40 coupe that had the same problem, i did it all to try to cool it. Finally i hit on the key -a stewart hi volume water pump, used a 6 blade alum. fan with as much pitch as i could fit in there, and made a shroud using alum. flashing material from home depot-about 2" or so wide that covered barely over 1/2 of the fan. Never ran over 190, even with a/c on in South Texas. Had a Walker rad. that never really worked well, and a small pusher fan in front in case--but i rarely used it, didn't need to. ----and a 180 tstat.

 

++ on the shroud; most effective thing you can do. If it runs cool on the road the basic cooling system is adequate and pushing more water through it won't help a thing. A shroud will insure that all the air the fan moves will pass through the radiator without regard to the fan's location.

 

Here is what I did with my '37 Chevrolet truck. The engine is a 250 inline with very low water pump. I dropped the radiator and moved it forward as much as possible. I made the shroud to fit the 17" fan. There is a lot going on in the front of the engine so it's hard see just how little room there is. I had to custom make a fan spacer to just clear the crank pulley and radiator core. Mine also has A/C in front of the AFCO radiator. I also added a smaller diameter water pump pulley to speed up the fan and coolant flow at low speeds.

 

A shroud will make a huge difference in your cooling, you want to pull all the air you can thru your radiator. If you can find the article in Street Rod magazine, it explains how without a fan the air bounces all over the place and can actually impede air flow.

 

Avoid parades, problem solved

 

I have a similar set up sbf with an overdrive trans .

the engine is really close to the rad and on a angle so diffficult to get a mechanical fan on it .

previous owner installed and electric pusher fan on a temp switch with a toggle override .

I pull the toggle switch once it gets to temp.
Has never given me a lick of issues all this summer.


But I don’t like it.

this winter I’m going to come up with a way to mount the rad 1”-2” inches away from the engine and install a mechanical fan, and a small shroud.

I will probably keep the electric fan also ( belt and suspenders )

bit with a mechanical fan and shroud I know it will always be moving air.

im not overly keen on electric fans.

if it’s your only option I would look at oem fans in a wrecking yard and see what you can get to fit .

 

With a tall rad like that, I would run ZIP's high rise water pump along with a fan shroud to really pull the air through.

 

Nicely done!

 

I made a fiberglass fan shroud for my Hemi-powered A sedan.

It began with two 1" wide by 0.5" thick MDF frames; one the size of the radiator core and one surrounding (and touching) the fan blades, with MDF spacer blocks glued between 'em.

An old T-shirt got stretched and stapled around the frames:

I smothered everything in resin and added a layer of resin-impregnated mat on the inside. Then I trimmed 0.5" off both frames' inner edges; giving max core exposure and 0.5" fan clearance.

Countersunk brackets attach to the rad/grille shell bolts.

I sanded then sealed everything with a thin coat of resin. More sanding & primer. It'll get painted later.

 

Run the biggest mechanical fan you can fit along with a shroud. Just me but I wouldn't be in a parade on a dare.

 

Four 6" diameter fans would be a GIANT step backwards in terms of fan area (so CFM specs of the respective fans need to be considered).
17" dia. = 227 square inches of area
6" dia. = 28.3 square inches each X 4 = 113.2 square inches.
Move the fan as high as you can to get to the widest grille opening possible and build a shroud. Be sure to include some rubber flaps in the lower area of the shroud to allow more air flow when cruising (look at 1-800 examples online to get some ideas). Good luck!

 

It looks to me like your grille is limiting your incoming air. (Custom grille?) Those grille bars look wider than the slots between each of them. That combined with the low fan and no shroud doesn’t stand much chance of cooling your engine.

 

I have not had a shroud on my 41 Cadillac but certainly it would benefit if I did have one. also I’ve never been in a parade situation. As it is I might consider a parade that has a steady downhill route on a comfortable temperature day.

 

Shroud,shroud,shroud, an put a large pusher in front of the radiator for parades!

 

I'd try moching up a shroud with some heavy cardboard and duct tape and then try iding on a very hot day just to see what happens.............

Lots of different opinions on how hot is too hot..........personally I always try to avoid any situation where one mistake can cause lasting results. Not letting an engine reach a marginal/questionable condition is always better than hoping you didn't .

 

I’m wondering if those forward facing vents don’t allow air to vent outward

 

Those “gangster” grilles limit about 1/2 the original flow. A real good fitting shroud and a 6 or 7 blade fan and possibly a smaller water pump pulley may be needed especially at idle. One really helped me.
I made a Fiberglas one for my sons race car with wood, cloth, and resin. I made it split in half for ez install and replacement. I now use the Speedway aluminum ones for circle track race cars.

 

I wouldn't worry about that, there seems to be a lot of open area there anyway.
If you look through the radiator you'll see that the tubes and fins in it block off a lot of it anyway, there isn't unrestricted air flow through it. A rule of thumb says that you need an air inlet about 25% the area of the radiator core to catch enough air at normal road speeds, any bigger and you won't get more flow through the radiator anyway, just turbulence as excess air redirects back out the grille again. At higher speed a smaller opening is enough, at low speed you're not using the speed to force air through the radiator, it's just the fan pulling it through so any bigger inlet than the open area through the radiator core won't be a restriction anyway.

 

I had trouble cooling my hemi because I didn't have enough water capacity in the cooling system....Had a 2 row with 1 and 1/2 tubes built and cured the problem and I live in Vegas....The brass radiator wouldn't cool it and it was from US Radiator super cooler....My blower motor was opposite of your problem...It would cool at idle but heat on the interstate....The blower builds heat when making boost because of compression....

 

If building a full shroud isn't possible, even just a half-shroud over the top of the fan and radiator will help increase airflow efficiency.

Do you have room for a 17" GM or Ford clutch fan? Those will move a lot of air.

 

Well you did answer your own question showing that you fully understand the issue. At least half of the radiator isn't getting air pulled through it when the car isn't moving at enough speed to get air through it. That is a hell of a lot better than most guys do.
I'd go with a shroud rather than fans. Even that fan will pull enough air though the radiator if you direct the air to it rather than past it.

Your fan at least looks like it goes fullwidth on the radiator, mine sits so low that I can't run as big of a fan as I need.














To me a shroud makes a lot more sense than small fans as that

 

A fan shroud would get my vote to maximize the air drawn through the core.

I also imagine that the reduced grille area and headers reduce the amount of low speed air flow in and out. ‘37 Chevs do not have a lot of grille opening.

My ‘37 has a Brassworks radiator and pump, Walker shroud, in a black car with a/c and has always stayed below 210 in 100 degree weather, although I don’t do parades.

 

Guys thanks for the replies!! Lot of really good info. I decided to make a two piece shroud. I've seen several examples of fiberglass shrouds but I'm more comfortable working with sheet metal so I'll go that direction. Avoiding parades is also excellent advice. I'll follow up with pics of what I end up making. Thanks again!!

 

I agree on all 3 of your points ✌️