Hot Rods FAN FLEX ??

I'm doing an engine swap in a very limited space. Wanting to use a stock steel fan. Queston is how much fan flex is there. What is a safe distance between the fan blades and the radiator core is enough.

 

enough room to change fan belts and more than the depth bolts are screwed into water pump should do

 

On a hard stop the 700 lb or so engine trans combo would be "push forward" 400 lbs or more on squishy rubber engine and trans mounts.
I might try a test tug to see what happens.
Or raise the rear wheels about 5 feet in the air.

 

You could make a radiator protector. This one was purchased, but they don't list it any more. Held on by zip-tie style trans cooler mounting kit.


Here is one on a Holman-Moody built '63 Fairlane to make it Period correct.

 

Much will depend on the stiffness of your motor mounts, radiator core mounts, and other connecting points.

From my own experience, I can tell you 1/2" was not enough on my '51 Ford F1. 351W, with stock radiator and MII mounts. It worked fine for about a year, but I was under hard acceleration once when I struck a dip in the road where a culvert had collapsed, making a nice V-shaped trench. Probably was only doing 25 or 30 mph, but it was enough to send the fan into the rad. Truck got a new rad and an electric fan after that.

 

On my 53 bel Air with a 350 I have less than an inch and it's plenty. Using a 57 Chevy fan

 

While steel fan blades do flex, the amount of flex varies depending on which fan. I would think a stock steel fan flexes a bit more than a Dreale steel fan rated for 8000 RPM. But as already mentioned the movement of the engine / trans unit, and in some cases radiator mounting, is a bigger factor than blade flex of a steel fan. I get concerned with less than 1".

 

It seems engine movement is more of an issue than fan flexing.

 

I'd also measure the length of the bolts holding the fan to the water pump pulley. When you're down to less than an inch, the bolt length will matter.
I've got about an inch and a half from the pulley to the radiator so that's probably enough but a 15-inch-diameter fan will interfere with the transmission coolant lines at the bottom of the radiator and I'm not finding any 14-inch fans. Any suggestions or is it time to fit the cutoff wheel to the angle grinder and go at my choice of 15-inch fan?

 

Cutting the blades on a fan is a risky business. The fan blades would need to be cut the same and hopefully stay in balance. If the fan blades are out of balance, the fan will wobble and wear on the water pump bearings. When the bearings get worn enough the fan will move all over the place and probably hit your radiator. I would advise not cutting the blades.

 

SBC? 58-65 style mounts?
It can’t move but very small mount as the steel mount parts overlap.
1/2” is plenty. I have run a flex fan for decades with that clearance.

 

Thanks for the heads up. Now to find that ever-elusive 14-inch fan. I just don't want to go down to a 13-inch fan, but will if I have to.

 

I'm using an old Hurst mount up front and a stock 5sp. mount in the rear. I'm having to cut into the Firewall to make room for the fan. Still maybe only an inch space.

 

bttt

 

1 inch is PROBABLY enough space, but as stated earlier, that will be dependent on the amount of movement allowed by the motor mounts, rad mount, body mount, etc. This is one of those build it and find out situations.

 

The plastic fans from Summit work really great. They don't flex forward, they are all to the back, no balance issues, and move a lot of air. They are also quiet. They are also black so hard to see.

 

Good info ANDY