Technical mechanical fan to radiator clearance, whats enough?

I just put an new ($$$) radiator in my 29 and the mechanical fan looks so much closer than it did during mockup with an old (no value) one.

I don't think this fan will flex much, and I build some mid mounts to keep engine from sliding forward.

what do you think a minimum safe clearance is?

 

I tend to be happy with 1" and a steel fan,no aluminum or fibergl*** for me. HRP

 

This is from Flexilite. Another source also says 1". I was wondering about your fan clearance when looking at your most recent pictures on your build thread. I am sure you will figure out some ingenious way solve this problem.

 

My 38 has 3/8" at the bottom and 1/2' at the top with no problems.. Just glad to see you're running a mechanical fan instead of those silly electric ones...

 

At this close, having enough room to get bolts in & out will be as much of a factor as blade-to-radiator clearance.

 

Closer than one inch and you run the risk of the blades coming in contact with the radiator with just a minor bump/fender bender. HRP

 

First off,I learned my lesson years ago about using old fans when, only by a stroke of luck that the blade that came off went straight down, did I avoid disemboweling a good friend who was standing on the front bumper of mt OT 4wd truck leaning over to reach the carb linkage and jazzing the engine I had just built and installed, using an old used fan. That blade chopped a half inch deep gouge into the asphalt. Think what it would have done to his belly had it gone straight up instead of down!
While you're shopping for a new fan blade look for one that gets all it's pitch from projection to the rear, not the front.

 

You know how an old metal radiator fan can experience metal fatigue, over the years.
Add the fact that some just have to rotate the engine by yanking on the fan blades.
Years back, a friend was revving his 235" Chevy for whatever reason, while under the hood.
A blade broke off, hurled through the air, struck him in the head.
He lost his life.
Moral to this story is never use a ****py old fan and never attempt to rotate the engine by tugging on a fan blade.

 

hmmm, you guys really got me considering my use of this old fan. i'll get a new picture the shows how much clearance I have now

 

3 places to never stand around a running car: Front, back and in line with the belts.

 

Like s**** metal 48 I've got 3/8" minimum and have had no issues in 4 years. I made it that close to eliminate a low speed overheating problem in a '34 Ford hot rod with original radiator and '56 265 Corvette engine. I even trimmed an original, stock fan (that I bought on eBay!) to clear the lower radiator hose. Before you laugh or cringe, I bought a few fans, picked the best one, chopped the ends off, balanced it, blasted it and painted it with 2 light coats of Barnes silver. A visual check for cracks is easy with the light color. I also mounted it with a factory GM spacer and grade 8 bolts. Of course I thought about the minor fender bender issue but I would rather have the peace of mind that getting caught in traffic won't be an overheating issue. It's a fenderless, hoodless hot rod. I don't run a fan shroud.

sent from the red phone

 

so I did a little measuring...

my 17" fan is 1 7/8" thick with 7/8 forward of mounting surface. and I have about 3/8" space to radiator and 1/4" to alternator nut/shaft.
I found the Derale low profile "Flex Fan"


will this flex much?
pull enough air at idle?
I suspect someone is using a fan like this........

 

those you have to run at 1" the tips tend to pull in when the speed goes up when they are new they live up to the name flex fan , they often flatten out as time goes on and just spin in the air instead of moving it and cause heat issues , they still make the factory 4 blade style steel fans and they are not that expensive if you look around , racers use them in mud cars as they hold up better and move lots of air . I prefer the fan in Oem mounting if not that 1" minimum so I can get at the bolts/nuts to take it off without pulling the radiator if needed ( put a cardboard or paneling protector over radiator ) I had one that was about 1/2" from the radiator and when the motor mounts went soft from age it slowly started to cut a arc into the tubes till it failed ( machined a nice circle where the hub was) ,I didn't think a engine moved that much .

 

A lot of old Fords came with less than an inch of fan/radiator clearance, and when the motor mounts got old or loose there were many of those circular marks to be seen on radiators. However with attention to maintenance it didn,t happen.
You've mentioned something about adding or building "side mounts" just exactly what do you have for engine mounts? pics?

 

Has anyone tried the Maradyne nylon fans ? They look to be flat front and rated for up to 8k RPM's, according to their website.
http://www.maradynehp.com/tx-twister.html

 

Watch using those aluminum fans. They'll cut ya fast and deep if ya slip with a wrench near them.

 

They have a tech line 800 number listed, call and ask about forward flex under power.

 

Exactly , my 36 is the same. Nothing I can do without shoving the motor back, re doing tunnel and carpet, moving trans, and shortening driveshaft. Not even room for a puller, have spal pusher on front but not sure how much it helps. When walker built their z radiator they added every bit of cover on the back demolishing my 1" clearance. Nylon flat fans are like having no fan at all.

 

As said above NEVER NEVER stand in line with the belts and fan of a running or revving engine. I have drummed this into both of my kids. It almost never happens, but when a blade does come loose watch out.

 

"TagMan", I have used the Maradyne fan once and it worked fine on a hooded model A.. I would use it again..

 

Thanks for all replies, I'm sure many hours of thinking have been spent on fan selection over the years.

I built a pair of these to provide addition eng/trans support and to prevent forward movement. (I have a 265 chevy that only has front eng. mounts) more pics in my signature build thread link



also I found a low profile "semi-flex" fan... the blades are aluminum and a lot thicker than the stainless steel. I don't think they will pull forward much....

https://www.summitracing.com/parts/hda-3617/overview/

 

Thanks for the feed back !

 

never stand in line with ANYTHING that is spinning. my neighbor just had a grinding wheel break loose and hit him in the lip and above his eye.

 

After the experience with my friend, I would NEVER do any kind of a build, without replacing the fan. After his event, I removed the fan from my stock 235, sure enough, fractures in the metal where rivets are located. In my opinion, nothing to think about, except to replace the fan blades with a new one.

 

You have done some beautiful work on your engine / trans supports !

 

thanks again for all the input, i'm going to go with a new fan that gives me more clearance....
bought this and removed the blue, plan to do alittle painting an install this weekend...

 

1" minimum for any type of Flex Fan.
Fixed Steel blades you can get away with less

 

those are as bad as no fan , they flatten out and make noise .. in the parts industry we called them boomerangs , as they went out the door and often returned a week later .

 

I disagree^^.. I've used the maradyne mechanical fan and it cooled my model A with full hood just fine.. It gave me more clearance and did not flatten out at all and made no noise.. Maybe I just got a good one and you got a bad one.. I would use one again.. Just my experience with one....

 

I like lots of clearance and a fan shroud. There is flex in the body mounts and motor mounts. The shroud serves 2 purposes. It makes the fan pull air through the radiator and it contains the fan if it breaks. We were required to have a metal shroud on the dirt track cars. The stock metal fans weren't designed for high rpm. The 65 to 66 Chevrolet shrouds were the most popular.