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Typically you would use an electric fan, the stock shroud and driven fan would be hard to work around. From the sounds of things, I'd stick to the spoiler and "track day" hood, punch some holes in the thing and be done.

Edit: I can't add the picture I wanted....search, "XJ hood vents" Jeep guys always have creative ideas, not used for high speed but to get the hot air out.
:thumbsup:

The other thing, since I'm thinking about it. Make sure your suspension is set up correctly for what you're doing. Searching the topic online I don't really see many early mustangs with a lot of aero work on them. Spoilers or splitters sure but not much else....just a thought.
 

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It doesn't seem like it will take much to make it safe at high speeds, vintage racers don't or can't make many modifications, and they seem to do fine. A picture might help of your hood/air cleaner. I assume you just want functional ram air ?
 

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Discussion Starter #64
It doesn't seem like it will take much to make it safe at high speeds, vintage racers don't or can't make many modifications, and they seem to do fine. A picture might help of your hood/air cleaner. I assume you just want functional ram air ?
I kinda ended up with a bit of a ram air setup, but it's definitely not sealed. I'll find some better pictures tonight.

I did find a link to a guy on the SN95 forum that took a stock hood and put a 2010 GT500 heat extractor scoop on/in it. Unfortunately, he crashed the car before testing it on the track. I'll find the link and post it here. American Muscle also sells vents - a bit pricey at $175 for the pair though.

Suspension setup, while nowhere perfect, seems to be more than capable of handling the track for now. I'd love to get coil-overs...but just can't afford them at the moment. Grab A Trak springs fore & aft, 1-1/2" front sway, full TCP subframe & cross brace, and Fays2 Watts Link. The car handles surprising well, and has impressed more than a few folks. :)
 

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Already some great advice in here. Just to add my experience; On my Miata race car I added an airdam & splitter with a horizontal under-tray extending back to the midpoint of the front wheels (couldn't go further back due to class rules) and hood extractor vent. It worked so well that the front end of the car became very planted at high speed, but the back end got VERY loose. High speed snap oversteer isn't fun! I spun the car in high speed corners at 3 races in a row and crashed it into the wall at a hill climb before I finally balanced it out with a big wing. I adjusted the angle of attack on the wing to balance the front aero, now the car is rock solid at speed. At 100+ mph it can corner way harder than the size of my balls will allow ;)

For the hood extractor/vent, it needs to be closer to the front of the hood than most people think. See the picture below of pressure differential across the hood. Usually placing it a couple inches behind the radiator/fan works best.



And here is the pressure differential measured across a Miata hood. The larger the negative number, the more pressure under the hood. You want to cut your vent where the largest negative number is, but obviously also behind the radiator.

 

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Discussion Starter #67
Already some great advice in here. Just to add my experience; On my Miata race car I added an airdam & splitter with a horizontal under-tray extending back to the midpoint of the front wheels (couldn't go further back due to class rules) and hood extractor vent. It worked so well that the front end of the car became very planted at high speed, but the back end got VERY loose. High speed snap oversteer isn't fun! I spun the car in high speed corners at 3 races in a row and crashed it into the wall at a hill climb before I finally balanced it out with a big wing. I adjusted the angle of attack on the wing to balance the front aero, now the car is rock solid at speed. At 100+ mph it can corner way harder than the size of my balls will allow ;)

For the hood extractor/vent, it needs to be closer to the front of the hood than most people think. See the picture below of pressure differential across the hood. Usually placing it a couple inches behind the radiator/fan works best.



And here is the pressure differential measured across a Miata hood. The larger the negative number, the more pressure under the hood. You want to cut your vent where the largest negative number is, but obviously also behind the radiator.


How'd you get those numbers?

Here's the link to the SN95 hood...and I was incorrect originally - he did another hood and did test that one, but as he was going for more of a cooling effect, I don't see much in the way of downforce results being mentioned.

My 70 dollar Heat Extractor Hood

I'm thinking of putting the GT500 scoop in, but closer to the nose like you mentioned. And would adding the side vents be overkill and/or completely destroy the integrity of the hood? I'll end up having it wrapped by a friend, so looks are not very important (just don't want to look ricer :shocked:).
 

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I haven't built my grill to radiator support block off yet. I keep hoping somebody will make a decent one I can just buy. I'm a bit tired of having to fab stuff.

This one looks like it might be decent but it is for the Eleanor 67-8. My opinion, the earlier ones they make do not look too hot.
 

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Discussion Starter #70
Air cleaner sits higher now due to a spacer and taller filter, but this is what it looks like under the scoop:
 

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That type of radiator ducting will aid cooling, but it won't help your aerodynamics any, since it doesn't actually reduce the volume of air entering the engine bay. You'd have to close down the grill opening for that.
 

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Discussion Starter #73
That type of radiator ducting will aid cooling, but it won't help your aerodynamics any, since it doesn't actually reduce the volume of air entering the engine bay. You'd have to close down the grill opening for that.
So, essentially, I need to block off the grill except to the radiator (and trans cooler)?
 

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That's the idea, divert the air around the opening. It may not be very effective with the blunt vertical nose of a vintage Mustang. Look at NASCAR, they have a sloped and tapered nose to divert air flow, with small openings.

Keep in mind, I'm just talking theory, I have no first hand experience.
 

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Discussion Starter #75
It makes sense. My '89 GT grabs air from a plastic scoop under the front air dam that is only as wide as the radiator. The grill is non-existent.
 

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Another idea is to use the air that is being forced in to the grill opening and ace the hood scoop. This is a lil Falcon but the idea is the same.
 

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If you are drag racing you're simply reducing drag rather than also creating downforce (up to a certain speed and then downforce becomes a concern again). For a drag run you want to close off the front and open up the rear to avoid anything that might create a parachute effect. You'll see guys with aluminum, or cardboard, covering up the whole grill. Even covering up huge front mount intercoolers, which on a drag run can act more as a heatsink than heat exchanger. Cardboard and duct tape took me from 104mph to 106mph.

Road racing is going to have similar philosophies for reducing drag but with other concerns such as cooling and the need for downforce. You want as much air as possible to pass through the radiator and then get the hell out and away ofrom the car. If you do it right you can reduce drag, increase cooling and gain downforce all at the same time. But it's also something where inches count and you can create something awesome or be an inch off and create something that doesn't do much for you, or hurts you. For the amateur who can't afford to have fifty different hoods and fenders, or do wind tunnel testing, I suggest KISS. Don't go too crazy trying to maximize aero with huge airfoils or by cutting holes in everything.

If you have a real mind for aero you can probably get a job working for a racing team. There's less aero guys than engine or suspension guys. I knew a suspension guy and an aero guy working in professional racing. One always had work and one had ups and downs. The suspension guy was a mechanical engineer with a good degree from a school that won Formula SAE every year he was there. The aero guy was a computer scientist and was totally self taught in aero.
 

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Discussion Starter #79
Car is setup for road course.

It's funny...I never much concerned myself with aerodynamics until this lifting started. I figured the car was 50yo and was definitely NOT doing what it was originally designed to do lol. Now it's fascinating. I hope to hit up our local vintage races here in August (I think) and get even more info.

Locating a track hood has proven harder than I thought. I suppose as soon as I stop looking one will pop up lol.
 

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Understanding the limitations of these, they could still be used as a foundation for additional hood/radiator/core support sealing or even just as inspiration. Another option since Sparky66 said he only found the one company making them:

67-68 Mustang : Undercover Innovations, Custom Show Panels for your Classic Car

I would at least consider something like this a tool, whether purchased or fab'd, in helping to manage airflow at the grill.
 
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