The Stovebolt Site Forums The Shop Area The HiPo Shop Fan shroud or electric fan?

Driving to work today, the temperature outside was in the mid 70s. I have an aluminum radiator and my engine temperature never reached 180° F. I have the factory fan on my 1965 SBC 283. I want to keep the fan because it keeps air moving inside the engine bay. When I had an in-line six engine in there and no mechanical fan, I was having issues with vapor lock in the fuel line, (but the fuel line did hover over the inline 6 manifold and was subjected to more heat than my V8 fuel line).

I was considering making a fan shroud so that the engine temperature would stay down at the traffic light. Right now the temperature will rise to 190°F or above. On really hot days here in SC, I imagine it would go over 200°F.

I think you can see my dilemma. If I install a fan shroud, the engine temperature will probably drop a few degrees because of more efficient cooling.

I’m thinking of going with an electric fan but would like to hear opinions. I understand that the thermostat controls flow of coolant. I have a 180° thermostat. If the thermostat is only partway open because temperature is not above 180°F, then the radiator efficiency is not as much of a factor. I already have plans in my head to make a fan shroud because sitting at idle the temperature will creep up to around 200° F.

Your temperatures are not out of line. Make the fan shroud and call it good. Electric fans just add another potential trouble spot in your fine looking engine Bay.

If cap is correct and not spewing, you are OK as Martin says. How far is radiator from fan blade? Wait till it actually goes over 200.

Jay, 190 is not that hot in reality. As the others have said I wouldn't be concerned unless it started climbing well above 200. Adding a fan shroud is a must for us in the south, it directs the air flow across the radiator and helps with keeping the engine bay cool.

You can fab one up easy enough or purchase an ABS plastic shroud for very little. I bought a shroud from H&H Classics in Bentonville Ar, for less than $80.00, bolted directly to the radiator mounts.

My recent experience with aftermarket products is not good. I seriously doubt that my fan would line up with the center of the fan shroud. My aluminum radiator sits in the factory position, but is not a factory radiator. I think I can make a pretty decent fan shroud if I put my thoughts to paper and plan well.

Jay, I am largely in favor of electric fans for a number of reasons. One is vibration and life of the water pump. Water pumps are no longer easy to find and they're costly...plus today's pumps are in many cases junk. That OEM fan blade is anything but nicely balanced. I've owned some that were terrible.

Your thermostat was designed to regulate water temperature and that's a good and an important thing. Please keep in mind it doesn't set the maximum temperature but only the minimum temperature. So it is a guarantee a 180 degree thermostat will let your engine temperature get over 200 degrees. Not that 200 degrees is that bad (as has been mentioned).

But a few will disagree (some vigorously) on the mechanical fan thing and I'm just here to present another viewpoint. If you go mechanical with a shroud, please remember to keep 1/2 of the fan blade inside the shroud and 1/2 outside of it for best efficiency. If you go electric, please get a good one. SPAL fans in my experience are the best you can get. I can tell you my experience has been an electric fan will keep your engine temperature at a more constant level. Good luck!

If the coolant isn't boiling, the engine is not overheating. There's a good reason today's temperature gauges have "cold" and "hot" indications, not degree measurements. "Hot" on a gauge for a cooling system with a 15 pound pressure cap is close to 260 degrees. People would get a case of hives if they knew how hot their coolant actually gets in a traffic jam with the air conditioner working hard, but the engine strolls merrily along!
Jerry

Mechanical verses electric fan. How many OEM are building with mechanical fans these days. Must be a reason why!

In the majority of cases it is because the engines are mounted the wrong way...

A lot of the bigger vehicles like the 2500/3500 diesels do still use mechanical fans because they move so much air it is not feasible to use electric motors.

That said, for comparatively small/low power motors I am all about electric fans. They operate at all travel speeds so you don't overheat in traffic, they make the AC work much, much better at low speeds, and they are quieter than mechanical fans.

I have used the factory fans from an early 2000s taurus on a couple swaps and been extremely happy with them. They are a two stage system that moves absurd amounts of air, comes pre-shrouded, and is $10 at any junkyard in the country.

That said, I am running a mechanical fan on my ls swapped 84 because I was too lazy to change it and the mechanical fan works just fine in this layout.

I had a 95 Impala SS which was the LT1 350. it had a two fan electric set up. If you turned the AC on one fan would run. If you got too hot the other would come on. The temp fan was two speeds. I liked it so much I bought a used one and put it in my Ford diesel truck when the water pump failed. That set up worked slick in there too. I am a firm believer in electric fans. You can easily wire them with relays and switches or with temp senders.

The thing that’s holding me back from buying an aftermarket composite fan shroud is that they do not provide any information on dimensions. I would hate to invest over $150 only to find out that it didn’t fit properly and then have to pay $25 to ship it back.

Hit the junkyard and get a set up out of a impala or corvette. They will have them stacked so you can measure them.

There is plenty of information on the web about Spal dimensions. Go to https://www.spalusa.com/ and you'll get dimensions, CFM, side view PDF's with dimensions, amperage draws, etc.

I’m referring to dimensions of the aftermarket traditional fan shroud for the mechanical fan.

**Update**
I found a vendor on EvilBay that was smart enough to list the dimensions in the item description. It doesn’t say where the centerline of the cutout is at the bottom for the radiator outlet but it looks pretty close. Hooray, I might spend some money here soon.

Fan Shroud Measurements: Height: 18" Width: 27" Fan Opening: 19-3/4" Depth: 8-1/2"


LINK TO SHROUD ON EVILBAY.

Given a choice I would go electric. Make sure you buy quality. There is a huge difference. I'll never go back. Mine has 2 speed fans. Cutouts for speed and temp and can be programed to run up to 6 minutes after shut off to cool the radiator. Set it and forget it. I have electric A/C with its own fan on a remote condenser. I also have electric P/S & P/B. I'm not normal. Thank you for your time.

OK, my 2cents: it is hard to beat the simplicity and efficiency of a mechanical fan. You already have a mechanical fan, just add a shroud (apparently mostly for your peace of mind!) and forget it. With a mechanical fan, only one thing can go wrong (the fan clutch), electric ones are not so simple...
Sure electric fans work well too, but good ones are expensive, you need sensors, relay, switches, wiring... And contrarily to what someone else said, they are noisy!
Keep it simple, stay mechanical!

It May sound strange but look it up on Amazon usually no charge return on it.

Since you've got plenty of room to work with, use a clutch fan that only locks up and pulls air when the air coming from the radiator is hot enough to need the extra air volume. Then build a shroud to fit that fan, if you still think you need one. The rest of the time, the clutch fan is just along for the ride, and doesn't rob horsepower or make a lot of noise. There's no point in putting up with all the noise and electrical load of any kind of electric fan that moves enough air to make installing it worth the effort, and a straight mechanical fan is "on" all the time, whether it's needed or not. My father's B-17 didn't have four 1200 HP Wright Cyclone electric motors!
Jerry

I run high quality flex fans on my small blocks in my 3100s. I have between 1/2" to 3/4" clearance from the aluminum radiator on both of them. The only noise I hear is the power steering pump.
I have a shroud on one of them which sits half way inside of it. It stays at 180 degrees all of the time.
I do not have a shroud on the other one yet. I still have to put the bed on it (its being held hostage by a miserable painter) and needs glass. I may run that one for a while without a shroud to see if it runs under 200 degrees with the A/C on.

For 90% of people a mechanical fan is fine and as stated simple and dependable. My primary radiator is about 8" in front of my mechanical water pump and not the right height. I'm also running a secondary Ron Davis hortazontal radiator with a Meziere's electric water pump between the frame rails with a Spal fan. I have Dakota gauges so managing them is easy. I have seen people make nice shrouds with restaurant cookie sheets. They come in lots of sizes. A shroud will keep your air from just looping around your fan and will give more airflow in your engine compartment. Thank you for your time.

Fan shroud arrived. I must be the luckiest guy this side of the sun. I might go buy a lottery ticket!
Shroud arrived undamaged. Molded plastic. Really sturdy too.
My current fan circumference is 18 + 15/16”. So let’s just say 19”.
The shroud nests over the radiator core perfectly. I could not ask for a nicer fit. Lower hose cutout is in the perfect location. (So years ago I picked a radiator off of eBay that actually has dimensions that match an original radiator. Pure luck!)
I have 3 fans blades to choose from. The 19” fan comes within 3/16” of the shroud and is too close for my comfort. The 18.25” fan is pictured and has about 5/8” clearance but the fan hub is thicker. In fact, the button on the end of the fan spacer only indexes in the inner 2 layers of the fan blades. That might be dangerous.
The smaller of the fans is just over 17”. Too small I think.
The fan spacer I have seems perfect. The fan blades enter the shroud part way. See photo.

I will ask a question and risk criticism.
Is it reasonable the trim an equal amount (about 3/8”) off the ends of the blades of the 19” fan to get it to measure 18.25”? I’d use a template to make sure each blade was trimmed the same amount. I’d also check to make sure it was balanced afterwards.

Or maybe there is a safe way to modify the 18.25” fan. The 18.25” fan has four bolts and 4 rivets that are all connected to the inner layer that DOES INDEX with the fan spacer.

I'm sure somebody out there will have another opinion, Jay but I'd go with the 18.25" fan. I haven't seen many pump mounted fans that ran anywhere close to balanced, so I would leave it be. Good luck!

The 18.25” fan is a good size but the outer layer of the fan blade sandwich isn’t indexed. That might be dangerous. The 4 bolts function as another form of alignment, so it might be ok. Another option would be to look for another fan spacer with a longer button on the end. That would solve everything.
It’s installed and no noises, so I’m happy. I could seal it up better where it meets the lower core. The pic shows some daylight coming through. It might not make any difference. Now would be a good time to add a warning sticker at the top of the shroud to avoid finger loss but the uninformed.

Link to video.

More advice is welcome.

At the risk of being repetitive- - - - -you have plenty of room to install a clutch fan. Just eliminate the spacer. If the centering button enters the fan hub at all, even 1/8", it will do its job. The BOLTS hold the fan on, not the centering button.

NEVER, EVER, CUT A FAN BLADE FOR ANY REASON! IT'S DEADLY DANGEROUS!

You could also drill and tap the centering button for a bolt and a flat washer. A little red LocTite will make the spacer and the fan blade a single piece installation.
Jerry

I don't think the 19" fan will grow under rpm. 3/16" should be fine. If it fits the button well I would go with that one first.

Second is the 17" If it fits on the button and spaced into the shroud right that one is a go as well.

I can measure my fan/shroud difference later today if you like.

I have to agree cutting fan blades is a no no is my book as well. I have never done it, but I lost a fan blade at rpm once. Thankfully it went down instead of up. Local kid was killed with a fan blade when I was in college. He was leaned over the engine bay reving the engine and it came apart and obviously went up vs down.

Alright lets look at this from another direction. The 18.25 fan is a great fit, the only issue is the index on the fan spacer hub. Is it possible to find a longer fan spacer and machine it down to the length you need and leave the index pin longer? Just an idea, don't shoot me...

Remember that the motor mounts are rubber, and the engine will move a little under torque loading. I'd want at least 3/4" of clearance between the fan blade tips and the shroud. Losing a little airflow around the fan is far better than listening to the fan blades creating their own clearance dimension the first time you get on a hard uphill pull.

In my shop, I'd thread the spacer for an Allen head bolt, and finish machine the OD of the bolt head to extend the centering snout, but I've got a lathe handy.
Jerry

The shroud itself could be easily clearanced.

The 18" is riveted and bolted together, looks like it's been that way from the get go, I would run it as is. I don't think I have seen a stepped fan spacer locating spud.
If this was a 7000 rpm race motor, I would think twice about it, but everyday driving, I would have it on and trying it out already.

It's not hard to spin a spacer out on a lathe and a rotary vice on a mill makes the holes easy. There are a lot of spacers out there. Find one a little longer than you need and take the material off the pin end to make the pin longer if you need to. It's always easier to find something you can alter. My 8 rib water pump pulley started it's life as a Ford reverse rotation pulley. I cut the groves in it and cut down a spacer then had them powder coated for $10. I have no idea what I'm doing and I pulled it off. Thank you for your time.