WDYD V8 swap cooling problems

What did you do....
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Swapped in a GM 350 when the original F failed and used the original cleaned and tested rad, with a 4 blade flex fan and modified shroud.
Should have rebuilt the F and stayed stock. The swap seemed like a good idea at the time.
I have a 180 thermostat and the engine runs around 200. On a hot day as high as 210.
I am looking at putting the original metal shroud back on the rad and installing an electric puller fan.
Research says the fan must have at least 2800 CFM for a V8 engine and that straight blades cool better than curved.
Does anyone have any experience with using an electric fan on an original rad, fan type and placement?

thanks
 
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FWIW I have a 2001 GM 6.0 lq9 , stock fj40 radiator, custom shroud and the stock GM clutch fan , cools great. Also, 200 or 210 is a little hot but not too bad, I would say it' s the 4 blade fan, try a diff one.
 

Zjohnsonua

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Swapped in a GM 350 when the original F failed and used the original cleaned and tested rad, with a 4 blade flex fan and modified shroud.
Should have rebuilt the F and stayed stock. The swap seemed like a good idea at the time.
I have a 180 thermostat and the engine runs around 200. On a hot day as high as 210.
I am looking at putting the original metal shroud back on the rad and installing an electric puller fan.
Research says the fan must have at least 2800 CFM for a V8 engine and that straight blades cool better than curved.
Does anyone have any experience with using an electric fan on an original rad, fan type and placement?

thanks

A photo will go a long way here. There's a right way to build a shroud and a whole bunch of wrong ways. We need to see what you're working with.

My personal experience was marginal cooling with electric (stock 60-series rad, Contour duals, and Derale PWM fan driver), and remarkable cooling capacity gains with the stock mechanical unit. It should be noted that the stock mechanical fan has 17% more swept area in this example - not an insignificant change.
 
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My last 74 had an older/rebuilt 350 swapped in it and was notorious for running hot. Custom shroud (any HVAC place can make a sheet metal shroud) and a SPAL/non-flex fan should fix your issues. Just my $0.02...
 
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A photo will go a long way here. There's a right way to build a shroud and a whole bunch of wrong ways. We need to see what you're working with.

My personal experience was marginal cooling with electric (stock 60-series rad, Contour duals, and Derale PWM fan driver), and remarkable cooling capacity gains with the stock mechanical unit. It should be noted that the stock mechanical fan has 17% more swept area in this example - not an insignificant change.
it is an 18" fan and it doesn't quite fill the shroud which has a 22" opening and is 5" deep. You can see that the fan is approx 3" from the rad surface

IMG_0852.JPG


IMG_0853.JPG
 

pb4ugo

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I've been running a sbc for 30 yrs. In the beginning I had cooling issues but nothing extreme. As for temp, keep in mind later factory fuel injected sbc's were designed to run around 200*. My carbed sbc 40 runs the stk rad, 160* tstat, a 5 blade 35 degree straight steel fan properly positioned in my fab'd shroud. It rarely gets close to 200* and that usually happens on long climbs while trail riding.

Looking at your pics, how close is the engine to the fire wall. As someone mentioned, if too close it can effect cooling. It seems you have a lot of room between the engine and rad.
 

thatcabledude

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Zjohnsonua

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In your case, the fan is in a shroud, but is not shrouded. This is bad. Start by ditching that spacer and see where the fan blades land relative to the shroud. That fan will have a hard time pulling much air volume at low speeds - just too few blades.

General fan / shroud design best practices leave the fan blade tips ~1" from the shroud (accounts for engine movement), and half the fan depth should run unshrouded in clean air on the engine side of the shroud. Kind of like the image below:

20220725_190725.jpg
 
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Zjohnsonua

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If you get a new fan, make sure you get one for the correct rotation, right @ceylonfj40nut?
 

thatcabledude

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I'd try a larger plastic fan with more blades that better fills the space and will move more air. Cheapest approach. Summit has a bunch. Shorter spacer as well
In a pinch, (or just being a cheap bastard😁) it looks like you could cut that spacer to length if you wanted.

With the proper tools to keep it square/true
 

ceylonfj40nut

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If you get a new fan, make sure you get one for the correct rotation, right @ceylonfj40nut?
Clockwise rotation fan and water pump for vbelt SBCs. Counterclockwise rotation fan and water pump for serpentine belt drive SBCs.

That fan looks like a pre-historic pteradactyl. Museum is only place that’s good for IMO.
 
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Downey

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So I'll tell you what we knew back in the last century. Use a massive 7 blade Caddy air conditioning fan off of a full sized GM rig, on fan clutch, blades bigger, blades have more pitch, blades rigid steel so they don't flatten out with RPM (when engine is the hottest)- - -this set up creates the hurricane inside the engine compartment to blow the heat out the tranny tunnel- - -ANY/ALL electric fans will not do that!!!!!. Fan blade should not be fully captured up inside a fan shroud, if so the air cavitates and can literally blow forward, back out the grille. The Society of Automotive Engineers did some fan/shroud test and found the engines ran cooler when the front edge of the fan blade was at the very rear of a fan shroud, barely inside the shroud.
 
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Thanks guys. I appreciate all the support. I'll have to figure out what works best in my current config. I don't really want to relocate the engine more forward. I will have to investigate if I can fit a large 7 blade fan with a custom shroud to move massive amount of air or if I want to use a 3000 CFM electric and build a custom shroud. Lots of great ideas, and information re fan placement that I had not known about.
If I go electric, does anyone know the optimum distance between the fan and the rad? Vendor supplied shrouds look to be less than 1" and some illustrations show the fan mounted directly on the rad.
Again, thanks.
 
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Thanks guys. I appreciate all the support. I'll have to figure out what works best in my current config. I don't really want to relocate the engine more forward. I will have to investigate if I can fit a large 7 blade fan with a custom shroud to move massive amount of air or if I want to use a 3000 CFM electric and build a custom shroud. Lots of great ideas, and information re fan placement that I had not known about.
If I go electric, does anyone know the optimum distance between the fan and the rad? Vendor supplied shrouds look to be less than 1" and some illustrations show the fan mounted directly on the rad.
Again, thanks.
I believe the suggestions were to get a shorter spacer to work with the current shroud. Jegs and Summit sell a bunch, or as mentioned it could be cut (Id just buy one though unless you have access to the right equipment.) Having it too far in creates turbulence in the shroud rather than optimum negative pressure to draw air through.

I found this link which may help: "If you have a fan shroud, the position of the fan blades in the shroud is very important to maximize airflow. Looking from the side of the engine, the fan blades should be half in and half out of the shroud. If the fan is too far inside of the shroud, it won’t pull as much air through the shroud as it could."
 

ceylonfj40nut

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I would buy a radiator/shroud/fan package if you go the electric route. I am in TX. It did not work for me. I don’t recommend electric fans.
 

Zjohnsonua

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I would buy a radiator/shroud/fan package if you go the electric route. I am in TX. It did not work for me. I don’t recommend electric fans.

x2
 
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I would accept Jim's advise with a couple of exceptions. First finding old 7 blade fans is not going to be easy and second I don't like clutch fans as they are just something else to fail. My compromise is to get one of these. You can get them in a size that fits your space as well as the needed direction.

I've been running a 17" since the mid 80's with no issues cooling my 350. Recently I converted to a serpentine setup and simply ordered the same fan in a counter-clockwise version. Also, from a performance standpoint, as RPM increases the flex of the blade reduces drag so it doesn't steal as much HP to drive.
 

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