47-55.1 Electric fan setup?

[MiraclePieCo]

Originally Posted by Matt_50

And being low on radiator like you said... from searches, a lot of people say a fan should cover 70% of the radiator.

Is this true?

That 70% figure actually comes from the Flex-A-Lite fan page. https://www.flex-a-lite.com/blog/whi...lt-driven-fan/
It's a good policy, but I'm here to say that I'm actually running a low-mount mechanical fan with a warmed-over SBC and my temp runs a consistent 140 degrees. The outside temperature here has been around 90 this week. Looks like I may actually have to install a hotter thermostat just to get my motor up to temp!

Regarding the tired old "flex fan decapitation" stories: My flex fan is rated for vastly higher RPMs than my motor is capable of; no doubt those fans that came apart were either cheap, damaged, abused, or all three. We know they didn't have a shroud!

I've used both mechanical and electrical fans. In every case the mechanical has cooled better. Plus I take comfort knowing I'll never be stuck on the roadside due to blowing a 15-cent fuse. My fan will never stop working as long as my engine is still running.

.

[Matt_50]

Yea, it is hard to ignore when a lot of people say the same thing... I guess there are probably plenty of people who say other stuff that just don't post.


I'm completely new at a lot of this so I do try to go with the general consensus unless a very experienced person let's me ask a ton of questions lol

[MiraclePieCo]

Originally Posted by Matt_50

Yea, it is hard to ignore when a lot of people say the same thing... I guess there are probably plenty of people who say other stuff that just don't post.


I'm completely new at a lot of this so I do try to go with the general consensus unless a very experienced person let's me ask a ton of questions lol

Ignore me too; laziness and poverty oftentimes compel me to do unorthodox things that are highly condemned on forums. I don't want you mad at me when I recommend something that screws up your truck!

[popstand]

removed

[Matt_50]

Thats an awesome picture of how you mounted it too.

[Daze57]

looks good !!!

[e015475]

A fan shroud made from an old T-shirt, fiberglass resin and some aluminum angle and sheet metal scraps.

Fan is a 16" Spal, but you could buy a smaller one and move it around to clear your water pump.

The money side..........



The back side that I fiberglassed.........



On the radiator..... (I'd just started sanding the resin to prep for paint)

[Matt_50]

What size radiator is that?

[MiraclePieCo]

My problem with shrouds:

An AD radiator core is about 19" x 21" = almost 400 square inches surface area.

A 16" electric fan in the center of a shroud is an opening of only about 200 square inches (A=πr2 or 3.14x8x8).

By covering your radiator with a shroud you have just closed off exactly half your cooling surface to ambient air flow. The entire 400 square inches of radiator front surface must force air through the 200 square inches of fan opening in the shroud. This is why some install passive flaps to allow airflow through their shrouds. IOW they cover the radiator, only to have to devise a system to uncover the radiator.

Yes, I've tried shrouds on my cars, but it seems like my fan runs too much. I've had better luck letting the radiator breathe.

.

[Marty68]

https://www.ebay.com/p/3-Core-Perfor...d=163168971034 has anyone used this? my "original rad is leaking getting price to recore".. but v8 sits very low with no shroud...

[e015475]

MPC - agree with you on fan shrouds that sit right on the radiator - seems like you're leaving some cooling capability on the table that way.

On my T-shirt fan shroud, the face of the fan is about 2" off of the radiator and the clearance all around the sides is at least one inch, so theoretically the big SPAL fan should suck air all across the face of the radiator - probably better in the 200 square inches directly in front of the fan though.

I think you'll find that the flaps on most production fan shrouds are there to let air flow across the radiator at highway speeds. When air pressure from forward speed is greater than what the electric fan can generate, the flaps bypass the fan. I think most production cars with electric fans can turn them off at highway speeds too.

BTW - the radiator in my photo is for a GMC AD truck. GMC engines were longer than the Chevy, so GMC sunk the radiator further into the core support and put a goose-neck filler on it to access the radiator. I believe it is about 1.5" deeper in the shroud than a Chevy.

[popstand]

MiraclePieCo is right, you don't need a shroud. Our trucks have a big radiator and a big grille - lots of air. That shroud is going to restrict air-flow thru the radiator and you're going to have cooling problems. These electric cooling fans are not full time, they turn on and off as needed. Yours will be on full time.

[e015475]

To each his own, I guess.

Around here, most custom cars/trucks have problems keeping the engine cool in stop and go traffic with the ambient ant 115F and the additional heat load of an AC condenser.

It really doesn't matter how big the frontal area of the truck is when it is stuck in traffic, because there's no ram air effect stagnating air in front of the radiator and creating pressure differential across the radiator- all that matters is the amount of airflow the fan can pull across the radiator. And it is just physics that a fan in a shroud (correctly designed) is more efficient than a fan just hanging in the airstream.

I can't recall a single production car I've seen in the last 20 years that didn't have a shroud to direct air through the radiator. Both electrical and mechanical fans seem to work, and anecdotally, it seems like there's a lot less overheating problems now than there was when I was a kid 50 years ago and these truck were commonplace. Engineering marches on.

It is your prerogative to run unshrouded like the fan in the pic of the previous post, but I'll stick with a shroud and a big fan where I can idle in stop and go traffic without overheating when it is 115F outside and 140F on the black asphalt. I'm resigned to sticking around this god-forsaken hell-hole in the summer, and I don't want the aggravation of overheating while enjoying my truck.

Best of luck with yours.

I've got to stop answering posts like these with a drink in my hand!

[Clarance J]

I had over heating problems with my truck with the new electric fan I put on. I didn't like it at all. I couldn't get all the switches, relays, thermostat and on/off plus the shroud I made (which did not work like I planed) wiring etc to work together. I decided to go back to the old flex fan I had before with new shroud design. This one worked really well. No more overheating problems. If you are interested in how I made it can be found in my build thread #333 thru 348. I went back to mechanical because there are way less things to worry about. Lotta work but well worth it to me.

Earl

[popstand]

I don't really care whether production cars today have shrouds. My truck will run just fine with no fan at all at normal road speeds. It does need the fan in traffic, stop and go stuff.

I'm guess I'm at a disadvantage here. Besides being a hot rodder for 65 years, I spent over 40 years involved in automotive powertrain development, mostly with GM. Included in that at one time was prepping prototype cars for climate wind tunnel testing at Harrison Division. Harrison made GM radiators.

[Matt_50]

I think I will try without a shroud first. Thankfully I don't live in Dallas anymore and I wont be sitting for forever at times.

But if I do need a shroud I like the cookie sheet idea.


If the fan tapers towards the end and looking t my first measurements.... Will a 16 inch fit?

[mick53]

Here is the fan I got for my 53 1/2 ton. Two rows 1 1/4" wide, all TIG welded. Claim 3300 cfm fan. 16 psi cap. 292/4-71 blower. Electric A/C, electric P/S.

[my56chevytruck]

Originally Posted by Matt_50

Should i make a fan shroud?

you don't need a fan shroud, although they help, and you don't have to mount your electric fan dead center of the radiator either. Yes, a SPAL fan is by far one of the best and I've used many styles, SPAL's do a great job.

[joedoh]

there are two types of shrouds, the first is used on an open bladed fan (air beater) to let the fan blades "pull" the air through the core. this already exists on electric fans, they have the shroud around the blades and dont need another to be efficient.
the second is the kind that covers the core so that ALL the air is routed through the fan. I have guys do that with electric fans but mostly see it on mechanical fans that never stop turning.

if your electric fan is your only fan, it cant hurt to route all the air through it, just make sure the fan isnt restricting the airflow, and even if it does a little the on/off cycle will probably make it a non issue. some guys use a mechanical fan on the motor with an electrical pusher for AC or overheats.

I like keeping mechanical fans where they were, my M3 came with a mechanical fan and the PO changed it to a complex two speed electric setup. he changed the placement of the three pin temp sender to the overflow tank, and the steam can affect the reading, so my temp gauge sometimes waves at me, even though there is no issue. first extra money I will switch back to a mechanical fan and shroud, and a high volume water pump while I am in there. overheating those 6 cylinders isnt a good thing, and I worry about getting complacent "knowing" there isnt really a problem when it starts climbing.

[Matt_50]

I've hooked up the transmission lines and I think a flex fan ( only mechanical fan that'll fit) would hit the lines. So I'll go with a electric one.

The temperature probe... should I use a thermostat housing with a spot for one made in it?

[popstand]

I wired my truck using a Painless Performance kit 10206, and a Painless 30102 fan relay with thermostat kit. There are two ways to wire the thermostat, one is using the thermostat as a ground switch. Attached are the two circuits. Install instructions and circuits for Painless products are available online.

[joedoh]

this is the one I used



https://www.ebay.com/itm/30MM-Silver-Water-Temp-Joint-Pipe-Radiator-Hose-Temperature-Gauge-Sensor-Adapter/264276874056

I had to open the hole with a drill bit and an NPT tap to fit the amazon temp switch. dont forget to hook up a ground if you are using a one pin switch.

[MiraclePieCo]

Originally Posted by Matt_50

I've hooked up the transmission lines and I think a flex fan ( only mechanical fan that'll fit) would hit the lines. So I'll go with a electric one.

You can get 90* trans fittings that will clear the fan, but I chose to install a remote cooler up front instead.

Originally Posted by joedoh

there are two types of shrouds, the first is used on an open bladed fan (air beater) to let the fan blades "pull" the air through the core. this already exists on electric fans, they have the shroud around the blades and dont need another to be efficient.
the second is the kind that covers the core so that ALL the air is routed through the fan. I have guys do that with electric fans but mostly see it on mechanical fans that never stop turning.

I'm surprised I don't see more guys using Zips elevated water pumps that center the fan on the radiator. Model A and Deuce owners use them alot, AD trucks seem like a perfect application.

https://www.ebay.com/itm/Zips-SBC-Sm...-/381219629028

[Volfandt]

I used the ground activation sender/relay method on my 49 GMC. Uses a single wire to the sender which I mounted in the water jacket passage in the intake manifold.

Also made up a home made shroud for the 2700 (rated) CFM fan. Been thinking about adding a couple slats in the corners that would flap open with increased air flow through the radiator via increased speed. They'd remain closed at idle.

[Matt_50]

Joedoh those look good and I like the price! MPC, thanks for the new info, I've never heard of those.