Hood vents

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Well... "manual" fans *can* be found easily that will out pull any electric on the market. But... I'm not sure that a small AL flex fan like that can make that claim. ;)


Mark...
 
Get a hold of TreeRoot and find out how did the louvers on his 80 series hood in Denver.

Ever think about installing a fan on the drivers side vent to pull air in? Do you have inner fender skirts or open air around the shock towers? Install some shorty headers and wrap them with header tape?

My 383 never ran hot, nor were my under hood temps that bad in my 40. I had a huge clutch fan from an old caddy pulling a lot of air.
 
Mark W said:
Well... "manual" fans *can* be found easily that will out pull any electric on the market. But... I'm not sure that a small AL flex fan like that can make that claim. ;)


Mark...
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first of all its a 18 inch 7 blade fan and people think they flatern out quick but they dont flatern out till high rpms which you are not going to be running. thats around 6000rpms. mine pulls enough air that the pusher i put on never comes on. mine runs all day in the heat around 185/195 thats when its about 100 degress outside. i do need to change the thermostat because during the winter it never goes above 160 to cold
 
The ones I have used flatten out at about 3000 or so. And simply do not pull much air even at full pitch. I have had a couple of V8s that would not cool with AL flex fans... Not sure I have ever had one that did cool well with them actually... but when swapped for a good MRK VIII fan these engines ran nice and cool.

Your fan may be completely different that the flex fans I have used... But I have gotten to where I just toss them in the corner and give them away if anyone wants them ;)


Mark...
 
when you say: "flatten out" do you mean they permanantly lose their shape, or the drag of them moving through the air causes them to lose their 'curve' while in motion?
 
They flex flat... loose their pitch due to the drag of the air they are moving. This limits the amount of air they can move regardless of rpm once this point is reached, and limits the drag at higher rpm as well.


Mark...
 
sounds like thin, soft material that isn't braced properly as fan blades. If they get "flexy" enough, what're the odds of them taking out a radiator?
 
I have ran both on mine and have the same fan mentioned above, at idle they both pull quite a bit of air. The 7 blade clutch pulled a little bit more so I used it as a safety factor for extra cooling capacity here in Florida. I didn't have a velometer to measure the difference but it felt like more air was coming out the hood louvers with the 7 blade clutch than the 7 blade flex. I have an extra 7 blade flex if you want to try it.
 
Bret said:
I have ran both on mine and have the same fan mentioned above, at idle they both pull quite a bit of air. The 7 blade clutch pulled a little bit more so I used it as a safety factor for extra cooling capacity here in Florida. I didn't have a velometer to measure the difference but it felt like more air was coming out the hood louvers with the 7 blade clutch than the 7 blade flex. I have an extra 7 blade flex if you want to try it.
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plus then you have the advantage of the clutched fan, allowing you to pull as much air as the relative temperature demands.
 
Mark W said:
They flex flat... loose their pitch due to the drag of the air they are moving. This limits the amount of air they can move regardless of rpm once this point is reached, and limits the drag at higher rpm as well.


Mark...
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Which is the whole point of a flex fan if I'm not mistaken, cause at the higher rpm, you're moving faster (in a normal car) and you have enough airflow through the radiatior at speed you don't need the fan, so why have the drag right? Just conceptually that's a bad idea for a slow moving 4x4 that can run higher RPM at slower speeds where there isn't yet enough air moving when the fan flattens out.


Anyway -

Assuming you have a good shrouded fan - mech or elect. and you've not done anything funky with your engine install that has screwed up the ability of air to escape, and want to add some louvers - you can either have them punched in as has been mentioned

Hot Rod Hood Louvers

$2.50 a louver doesn't seem like a bad deal

or just cut and paste...

Gen-Right Hood Louver Set, 2pc Long BLACK

RunCool Real Heat-Escape Hood and Side Louvers
 
Combat Chuck said:
sounds like thin, soft material that isn't braced properly as fan blades. If they get "flexy" enough, what're the odds of them taking out a radiator?
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They are never flexed beyond the elastic limit of the aluminum so breakage is not a concern.

It is not braced because it is intended to flex to a smaller pitch. So considering the intended purpose of the fan, lack of bracing *is* correct bracing. :)


Mark...
 
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Combat Chuck said:
sounds like thin, soft material that isn't braced properly as fan blades. If they get "flexy" enough, what're the odds of them taking out a radiator?
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I think that is why they call them "flex" fans.;)

When I had a hood and fenders and my rig was a daily driver I put hood vents on my truck and it helped drop the temp of my small block chevy a few degrees. I got them from a marine supply store. They use them on the sides of the engine cover on boats. Getting your hood stamped looks cool but can be costly.
The challenge is getting them mounted on the hood in such a way that the holes don't disturb the struts on the underside of the hood. I reccomend it if underhood temps are too high.
 
when i ran my 501 caddy i used a carb cooling fan mounted backwards blowing out the side vent .im sure any 12 volt fan could be mounted under the hood vent for more air flow.
 
I just cut 2 of the cowl louver sections out of a rust bucket '74. They could be trimmed and grafted to a flat section of hood. Send me a PM if interested.
 
Sorry for the tiny pic:

m_aa826729042b48fd8d4166c0e52772e9.jpg


I believe the stickers are part of the cooling system, but the external hood fan is key.

miklos.webp
miklos.webp
 
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That there is funny now...I dont care who you are...

Just leaving the wheel wells open on my 45 made a huge difference. Driverside mostly, because thats the side the fan pushes the majority of air to. Dropped temps 10 degrees. I run a single 16" Spal fan on a custom shroud.
 
Combat Chuck said:
sounds like thin, soft material that isn't braced properly as fan blades. If they get "flexy" enough, what're the odds of them taking out a radiator?
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a flex fan like in the picture is designed to "flatten out" at a certain RPM...that's the ony way it controls the air flow.... personally I like a OEM clutch type radiator fan.
 
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