Technical Any Issues with Shortening Fan Blades?

In a desire to get rid of the noisy-ass flex fan on my avatar, I bought a fan/clutch assembly and u-fit shroud from Summit. It's been kicking my ass right from the start (first part I removed was the fan; the PO managed to screw metric bolts into the 5/16-24 water pump hub... came out hard, all the way, and it all went downhill from there) but I'm finally gaining on it.

I ordered a 19" wide shroud and a 17" fan, figuring that would give me adequate room to fit the fan. Turns out the shroud is actually 18" wide, the other 1" was mounting flanges (which I ended up cutting off anyway). Basically leaving me zero on the sides once I cut the hole big enough, and a flimsy install. I can't find a steel clutch fan smaller than 17" (Flexalite has an 16" aluminum one, but it's only rated to 4K rpm), so I'm planning on clipping 11/16" off the end of each blade. I figure as long as I cut exactly the same amount off each blade, I shouldn't have any issues....

 

Should be fine. Buddy of mine is running a fan on his flattie that he cut down quite a bit.

 

No issue cutting. The rpm rating, that's another issue. Only 4,000?

 

If you are worried about throwing it out of balance, I would think that one of the lawn mower blade balancers from a hardware store should work. A cone on a post deal, kind of like an old bubble balancer.

 

I believe the 4000 RPM deal was just a comment about a fan that @Crazy Steve isn't going to use. That's my understanding anyway.

(Flexalite has an 16" aluminum one, but it's only rated to 4K rpm)

 

The steel one I have is good to 7K, the aluminum one was only good for 4K....

 

In addition to making a template and sharp scribe lines, you might consider this. Get a sensitive scale.....weigh the fan before you cut anything. Remove the desired amount from one blade....weigh the fan. The difference is how much you removed. Repeat for each succeeding blade.

 

Exactly that . Do you really thing they spin balanced that fan from the get go. Just cut then trim to final length via angle die grind with sanding disc and use a pointer as reference from a pivot point fixture of some sort.

 

There’s a lot of crazy fans out there

 

Seems like you’ve got your hands full with coverage of PO sins. Don’t make your own sins to make those PO sins not as bad

A shroud and fan need to be RIGHT or they don’t work RIGHT. If cutting a good fan blade is what it takes to get a universal fits nothing shroud to work right then do it. I’m guessing you’re going to get it to fit but not necessarily be RIGHT. Lots of effort to just get it to a level where it’s better than it was but still not as good as it should be.

 

Do you really need the shroud?

 

I am going to take the opposing view, I don't like the idea of timing a fan, a lot of research when into keeping them balanced, cut it if you wish but if it were me I would look around and find a fan a bit smaller. HRP

 

You can always glue nickels on it like a ceiling fan. (Sorry)

 

Years ago I had one of those aluminum fans come apart and stick a blade thru the hood top on a deuce sedan. Since then I've used steel fans.

 

Some people call it a Kaiser blade

 

The odd looking fan spacing is done to break up harmonics that occur during operation. This reduces chance of damaging components like the radiator - similar to avoiding a natural frequency vibration. It will also be balanced as well.

 

hmmm..mmm

 

I thru a blade off a stock 60 chevy fan. It went thru the shrould and the inner fender. I bought a large diameter Vett pully.

 

I agree with 31Vicky and HRP. I think leave the fan alone and make up or refit your shroud.

 

I would NEVER cut a fan down. It would be very easy to add to the diameter of the shroud then mess with the fan. Or buy another shroud that fits the fan you have.

 

Guess not everyone has ever cut a prop that turn @ 15,000 to 17,000 rpm?

 

Did you search flexalite’s web site directly? I couldn’t find the proper size fan through summit but flexalite’s site listed one. I just adapted the part number to match summits system and it popped up when typed in the summit web site search.

 

Trimmed the fan on a flatfender jeep to accomodate an F-head 134 motor swap. Worked fine. I just tried to keep all blades close the same length.

 

I have cut steel fans with no issues. Make the first cut , then use that as a template for the other blades.

 

I think cutting it might work, but I wouldn't do it. I considered it myself, and I own a blade balancer. Flex fans are an another issue. I have a factory steel flex fan from a 77 C10. I was informed by GM that they do come apart. But since it was so old, they were not about to replace it, at no charge. I have run an aftermarket flex fan on other engines. I was not thrilled with their air moving capacity. Nor do I have any way of knowing if they improved mileage, or increased performance, which was one of their selling points. My uncle ran a radiator shop for years and liked clutch fans. But he never put on his car, that I can recall. So that said, I'd take a long hard look at the shroud. Better to fix that, and eat fan blades.
Good luck!

 

Way back in the early '80's, I helped some friends with a dirt Late Model, and they were concerned with every ounce of weight, along with balancing anything that rotated. They had a water pump that they used to balance the fan and pulley with, I am pretty sure he removed the seal from it to eliminate the drag. As long as you maintain balance, removing material from the ends should cause no issues, especially if you finish them off in a way that would eliminate any stress risers. Those balanced fans were run a little under crankshaft speed, which would reach 7500 rpm for up to 100 laps.

 

If only I had a choice.... The original builder of my avatar did multiple things 'differently', using what I'll politely call 'unique' solutions to issues. The issue here is where the radiator is and how its mounted. Now, before I go any further, just let me say that this ain't no catalog car; other than the M2 front suspension, every other 'specialty' part on the car was either modified stock with used parts or scratch-built. This car was built the old fashioned way, and you have to admire that. But I don't have to admire the design/engineering decisions; I've had to rework three other 'design flaws' since I bought the car, this just turns out to be the next one in line. I'll also admit I didn't look at it close enough before ordering parts although I know now that it wouldn't have made any difference; I've got the right parts (or as close as I'm going to get), it's just a very difficult job.

So back to the fan shroud. The radiator has been pushed forward about 6" from the stock location. In the new location, I have 5.5" from the end of the water pump to the radiator; not enough room to install a fan if moved back. The builder was generous in firewall-to-engine clearance, but I'm sure as hell not planning on cutting out all the mounts, shorten the driveshaft, etc. to move the motor back. Yes, there's shorter water pumps, but I've got the '62-65 all-aluminum cover/pump on my SBF, so I'd have to change that to do anything different.

So the radiator stays where it is. Now, this was another 'unique' design. The radiator is 18" wide (as wide as will fit in the space; Anaheim Radiator built it well..) but has no mounting flange of any sort. Instead it has two 'U' shaped brackets (one on each side) that attach into the two bolt holes in the top of the radiator support yoke. Sounds and looks hokey, but is surprisingly solid once bolted down. Been there a long time like that, it does work. But if I try to install any sort of conventional flange or use a wider shroud, it will block access to these bolts; they're already hard to get to. And to throw one more turd into the stew, the engine/radiator centerlines are offset by 1/2", so while a 18" shroud and 17" fan theoretically would work if everything were perfect, it's not....

All of the above was the easy part; the real challenge has been fitting the shroud. Because the yoke is now between the radiator and the engine, I have a diagonal brace running across each bottom corner of the radiator. The yoke has to stay, that's the part that attaches all the front sheetmetal to the frame. So the shroud has to be notched to clear the braces, but has to be tight enough to avoid too much 'leakage' around the braces. My old carcass won't go in there far enough to really see, so I've been sneaking up on my trimming so I get a semi-airtight opening. I've had that radiator in and out of the car more times than I can count... but I've almost got it, one more day should do it.

If I ever pull the front clip to reconfigure the radiator support and have the money for another radiator sized differently, all this could be addressed. But right now, cutting down a $40 fan is the best option....

If anybody is interested in pics, I could post some in the next day or two...

 

The car has never actually overheated, but has come close more than a few times. The existing fan was 19" (wider than the radiator) with no shroud, but it's noisy as hell; that's what started all this. I figure the improved efficiency with the shroud will offset any fan size difference, as well as helping reduce the noise.

Worst case, if it doesn't work out I can pull the fan/clutch/shroud and reinstall the flex fan (with non-metric bolts this time... )….

 

If cutting that fan solves an issue then do it.
If cutting the fan creates several more???

Just to remind others who come here looking for answers - cut it evenly and make sure it’s balanced.

 

Hey Steve, I'm another one who has trimmed/cut a fan blade (without issue).
I think you'll be fine, I seriously doubt any minute difference (If any), would present any problem.
Isn't it fun, detecting/correcting po's ingenuity (I'm sure some people who've bought my cars, are scratching their heads).
Why do people do..what people do?