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hotrod1994 07-09-2013 03:40 PM

the stock shroud is tight real tight like 1/4 inch of clearance i never had one before and it helped a little but not enough
maybe ill try spacing the flex fan out some more how far away should the fan be from the radiator?

TheYellaBrick 07-09-2013 05:02 PM

Moving that flex fan deeper into the shroud won't help a bit. Change out to a stock type bladed fan or clutch fan or electric pull type.
The flex fan design is made for it to turn into a low drag disc at speed, and as such will prevent larger airflow rates through the flattened blades.

hotrod1994 07-09-2013 05:44 PM

ok so mount the electric fan on the engine side of the radiator and pull the air through right?

bjuice 07-09-2013 07:16 PM


Originally Posted by hotrod1994
ok so mount the electric fan on the engine side of the radiator and pull the air through right?

Hint ......

Just make sure the fan's polarity is wired properly and the fan is pulling indstead of pushing if your mounting on inside of radiator. This mistake can be made pretty easy if you do not check the pull of the fan before you final mount.

hotrod1994 07-09-2013 11:55 PM

yeah i planed on checking it
thanks guys
i appreciate all the help

roadkill2 07-10-2013 06:49 AM


Originally Posted by hotrod1994
how should i go about checking the the temp at the bottom hose on the
radiator? ir thermometer?

and the flex fan is 3-4 inches away from the radiator so ive got a felling its not getting enough air flow

1) Use a IR temperature gauge. You know, one of those with the laser dot for aiming when you pull the trigger. If you don't have one, you don't have one of the right tools to be drag racing . . You use it for everything. Engine temps, header temps to see if all cylinders are firing, track temps, tire temps, even wife temps . .

It doesn't matter how far from the radiator the fan is, if it fits in the hole in the shroud with about 3/4" all around it. The fan should also centerline or be just slightly inside the shroud. Preferably the Fan blades should be at least an inch or two (or further) from the radiator. The fan creates a vacuum in the shroud and pulls air through the radiator and the closer to the radiator it is, the less area is exposed to moving air. In other words, if you have a 17" fan and it's a quarter inch away from the Radiator, you're only using a 17" circle in your radiator to cool your engine.

On the Flex Fan. It should work just fine for the symptoms you have described. A "Flex Fan" is designed to flatten out as the fan's rpm increases and to pull LESS air as it does. At low rpm the fan's efficiency is the greatest, and the least at high rpm . . it's designed to create less parasitic drag or HP loss at higher rpms where you have moving air that takes the place of the need for a fan . .

The problem with any mechanical fan in racing applications is that they're generally riveted together and tend to come apart at really high rpms . . And if you've got an engine you're gonna buzz into the real high 6's or touch 7000 rpm plus, you should go to a constant speed electric water pump and an electric fan. It's just one thing less that's sure to fail, sooner or later . .

oldandtired 07-10-2013 06:56 AM

[quote="roadkill2"]

In other words, if you have a 17" fan and it's a quarter inch away from the Radiator, you're only using a 17" circle in your radiator to cool your engine.

On the Flex Fan. It should work just fine for the symptoms you have described. A "Flex Fan" is designed to flatten out as the fan's rpm increases and to pull LESS air as it does. [quote]

x2

I had a flex fan on a 331 SBC and was racking the throttle from beside the roadster. The fan blades flexed foward and cut into the radiator. Thankfully I was sprayed with warm water, not hot!! :shock:

roadkill2 07-10-2013 07:09 AM

[quote="oldandtired"][quote="roadkill2"]

In other words, if you have a 17" fan and it's a quarter inch away from the Radiator, you're only using a 17" circle in your radiator to cool your engine.

On the Flex Fan. It should work just fine for the symptoms you have described. A "Flex Fan" is designed to flatten out as the fan's rpm increases and to pull LESS air as it does.


x2

I had a flex fan on a 331 SBC and was racking the throttle from beside the roadster. The fan blades flexed foward and cut into the radiator. Thankfully I was sprayed with warm water, not hot!! :shock:
You had one with the long skinny rectangular blades, didn'tcha? Like I said, you get a lot more efficiency from a shrouded mechanical fan if it's back aways from the radiator. Basically, you get to use ALL of the radiator, not just the area the fan pulls air through directly in front of the fan.

I learned all this from my time at "Hard Knocks U" which was about 3 years of street rodding (About 20,000 miles) in a '34 Sedan with a blown SBC . . with a smaller than stock water pump pulley on it .(Unbeknownst to me) I even had a custom built Electric "S" fan from SPAL ($437) . . Bought a shroud from Walker, put on a cut down "Skinny Blade" Flex Fan (had to build a custom fan spacer) and have no more cooling problems . . But I could write a book . . about both the solution(s) and all the goofy and sometimes applicable advice I got from everyone from cooling engineers to little kids . .


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