Having replaced the radiator in Clarence with a new aluminum one, with the lower radiator hose connection moved all the way to the corner of the tank, and mounted lower, I can now install a larger fan. For many years I had to run a 14" fan but now can go up to 19", the largest I can find. However, now I'm way too confused by the available options. For 99.9% street/highway driving, what are the pros and cons of the various types? Opinions welcome, but reports of actual experience requested.
I used a flex and it seemed okay. BUT.... every person I talked to that had a steel, fixed blade fan, swore by them. It seems with cooling issues, everyone's results may vary.
I always felt clutch fans are the ultimate choice. They free up some power as well as offer cooling 'as needed' by virtue of the spring/clutch used. Flex fans are noisy in some apps, and some like the noise but I don't. As to what flex fan, my experience was with a BBC and I went from a clutch fan to a plastic flex fan driven by a Moroso electric motor kit when I went racing. Always ran cool but there was no street time involved. I don't even know who made the fan, it was black plastic, maybe 6 blades, moved a lot of air.
Did the exact same thing on sbc racing & on street worked great for both situations, still on car 30+ yrs. Now v belt driven with alternator. When racing, went through the lights at 7800 rpm...many, many times. I believe it is a moroso fan. Sent from my SM-T217S using The H.A.M.B. mobile app
I run a flex fan in my Ford with a shroud, a brand name one from Summit, maybe a Derale. I had a steel fan in it and it ran hot in traffic. With the flex fan it really helped at slow speeds. It is a little noisy when I hit the loud pedal hard, but an improvement over what I had.
Look for Engine Masters ep 20 on youtube. They did a cooling fan test for hp losses. Good looking traditional fixed blade steel fan lost about 30 hp if I remember right. Everything else was better from that standpoint.
The way I remember it was the plastic fan was the worst. That's what we ran in all our race cars, if we only knew!
I like to look to the OEM to see what they did, because they had to make stuff work and last a long time. If it's something that doesn't need the ultimate in cooling, a simple four blade steel fan works fine, and was used in millions of cars from the 20s to the 70s or so. If you need more, a 6 or 7 blade steel fan will move more air, but make more noise and take more power. Clutch fans started in the late 50s for the cars that needed maximum airflow through the radiator, and were usually combined with a shroud. In later years, they went to plastic fans, and electric fans. If you are building a car to modern standards of efficiency, these might be the way to go...but be sure to get one that is OEM quality, not crappy universal cheap quality. Both of my rides have big engines, they both have clutch fans.
I had a flex fan on my chevelle until a blade flew off. I went back to a factory six blade clutch fan and it cools better than the flex fan by 10-15 degrees. With a solid lifter cam and headers i dont hear the fan.
Back when we were dirt racing this was the best fan we could find. It's a factory GM fan, but I don't know what from. It's big though, and might be overkill for a street car. We may have lost some power pulling it, but " if you want to finish first, first you have to finish." Other than wrecks, running hot was the biggest cause of aDNF. Good luck
I have an OT Chevy Duramax diesel p'up that uses a clutch fan to very good effect, no cooling issues ever. On my sbc powered Hiboy I didn't have enough room to install a clutch fan, so I used a Zip's water pump riser and a six blade fan from Speedway, bought a shroud, but never installed it because I haven't needed it. I am aware of the Engine Masters video and have watched it. Have no doubt that a conventional fan eats horsepower, but I find myself wondering about a variable that I don't think was considered in that dyno test: What about the effect of forward motion of the vehicle and the airflow from that reducing the effort required to spin the fan? In any event I would use a clutch fan where the vehicle allowed room for the clutch.
Mike, I have been running the Flex-a-lite Nylon fan on my Coupe for the past 29 years and it does the job fine.
17" 6 or 7 blade steel fan with a clutch on my 51 Fleetline, with a SBC with a shroud. No problems anymore.
I have run the stock steel with clutch, fiberglass flex fans, and electric (attached to the rad). From my experience, I prefer the clutch fan or the electric fan. I used an electric fan to cool my big block 55, with a stock 55 rad, for the last 30 years in all driving conditions, including hauling a camper on the freeway at 70 plus mph. I have two other, off topic big block cars that use clutch fans with excellent results. I also swapped a Ford engine into my Bobcat loader, and it has been using an electric fan for the last 30 years to cool the water and the hydraulic oil. One of the other posters mentioned it, but a tight fitting shroud is important for the efficiency of the fan. If you are overheating when you are idling around or are in traffic, you need more fan, or larger radiator. If you are overheating when you are on the highway, you need more cooling capacity. Bob
That Engine Masters fan comparison video was a real eye opener on parasitic drag and power loss. Saw it a couple months ago. For those that haven't seen it. The same engine was used, they only swapped the fans out and did identical dyno pulls. So they have numbers backing up their test, not just butt dyno. If the OP isn't worried about power loss, no big deal, but just neat info to have.
that engine masters dyno test left out one very important thing...when you are driving, the car starts moving, and the parasitic loss goes way down when the car is at speed. The dyno just sits still.
There are many fans , and just as many applications , Derale part number DER17517 17" around 50 bucks. .
On that "ol" farm truck i refer to once a while, i used a 10,000 flex fan, yes they can be a bit loud, but they deliver a LOT of AIR at the LOW rpm range that the truck operates in, WAY under 5,000 rpms, and Good AIR at idle, where we need it, see DIFFERENT fans for different applications. 10,000 fan picture---> .
This 17" all steel fan is what I use on all my hot rods,I just ordered another to replace a electric fan on the mordor. This makes the 7th I have used and my cars NEVER run hot! HRP
FWIW I had a clutch fan fail and lock up at 60pmh on cruise control. The car slowed like it hit a snow drift, and it sounded like I'd been buzzed by a prop plane. Then the cruise control started adding throttle and the whole works scared the crap out of me. So, I know those clutches work, and that they do use substantial power when fully engaged. They're my first choice whenever I have room.
years ago a coworker had me test drive his car, because he though the transmission was acting up. The fan clutch was locked up..... yeah, they do work, most of the time.
This is where I'm leaning. 19" Derale Rigid Race Fan from Summit. Anyone ever used one of the "add on" clutches? Any experience you care to share with us? I'm thinking I'll put on the 19" steel fan and maybe in the future add a clutch if it looks like it might be worth it. Right now I will use a 2" spacer (that's already there on the 14" fan I'm currently using) between the water pump and the fan. The clutches look to be a couple of inches thick so it should bolt right in there in place of the spacer.
You want a clutch fan, a thermostatically controlled clutch fan. It would be perfect in old Clarence.
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