I have a 2025 Dark Horse Handling Package which spends a good amount of time on the track, but is a dual purpose car that also sees a good number of street miles. Bought it in January and it's got nearly 6k miles on it so far. The cooling system on the car is overall very good. I do see temps getting up around the 240F CHT range and 280F oil temp range, which from reading up is pretty common and not concerning. I have gotten to where I've felt the engine start to pull some power, and if running windows closed and AC on I'll have a few cases where it'll turn the AC off (which appears to be related to temperature, although I haven't experimented enough to figure out the exact times that happens).

I am considering a hood modification of some form to improve airflow and thus cooling. While it's not "needed" per se, improving cooling isn't a bad thing. I am also looking at potential (minor) downforce improvements that some options advertise which, again, not a bad thing, although not something I'm looking at as likely to improve my times by any meaningful amount.

Right now I'm looking at options of either modifying my hood with options from Race Louvers, or buying a replacement hood that has vents in it. A friend of mine bought an eBay aluminum GTD replica hood for his S550 that he's happy with on quality and has removable vent covers (so the vents are functional), but he hasn't (and doesn't plan to) track that car, so there's not any data I can go with from him. Logic would say it should be airflow an improvement over my stock hood (and look cooler) but logic and aerodynamics don't always align. The particular one he got (but for my S650 vs. his S550):


Bunch of AI generated photos that don't give me a great warm fuzzy but such is the world these days.

Since the car is still a street car, I don't want anything I do to significantly impact the streetability of the car, and I am looking for function. So I don't want a hood that's super fragile, don't want something that's going to increase my weight vs. stock. Hood pins I'd be fine with if needed. In general I'd say I would prefer to not cut up my factory hood, but if that's going to give me the best results, I'm game.

I have looked at some of the DH-R service bulletins on modifications. I don't particularly want to cut up my stock fan shroud as I think that may hurt my street (i.e. sitting in traffic) cooling, and I don't really want to remove the stock grille and put mesh in, but that's one I'd be more open to.

Curious what others have done and would recommend, or if I'm barking up the wrong tree.

Have you looked into any offerings by Anderson Composites? Not sure what S650 options they have, but I have been considering getting a CF hood from them as I don't want to cut my OE hood.

Deadly0ne said:

Have you looked into any offerings by Anderson Composites? Not sure what S650 options they have, but I have been considering getting a CF hood from them as I don't want to cut my OE hood.

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I have. They offer a GTD style as well as two other vented hood styles, and are another consideration. Another produce they have that I'm looking at is the full-span Gurney flap to replace the 2/3 factory Gurney flap that the car came with from the factory (which should increase downforce slightly).

I'd be curious what anyone thinks of their options as well in terms of performance, quality, fit, etc.

The ones I'm finding for my car:

Well as often happens, seek and ye shall find. I did some looking around and found that American Muscle also sold the aluminum GTD style hood I was considering. And, they had 2 open box ones, one at their Kansas City warehouse, which is about 30 minute from my house - thus saving the $200 "oversized item" shipping fee. I picked up that one, so if anyone else is interested, they still have one in their PA warehouse. Since I saved on the oversized item fee, it came out to $600 out the door. That's cheap enough to make it worth trying out. My son and I picked it up.

Initial impressions are positive upon inspection. The vents are functional, and you can either leave them fully open, honeycomb in, or fully closed (with covers that screw in from the bottom).

I'll report back once I install it. My next track day should be in 2 weeks, so I'll be able to test it then.

Can you post some pictures? You'll probably want to run some gurneys ahead of the openings to help the extraction. Having the open holes don't mean much if there's nothing to spoil the air going over it.

Here's a few pictures, I got it installed yesterday. I thought about adding a Gurney flap in front of the vents, and that may be necessary. The pictures don't show it well, but there is a lip just ahead of the vents. Running my hand over it, I can see where it would push air upwards and create a negative pressure area above the vents. Having never seen a GTD in person, I have no idea how this compares, but I would think that Ford made whatever ventilation it had functional given the heat load it has to dissipate.

Upon installation I found some more imperfections in the hood. I would say that's largely because of the clearly thinner gauge aluminum that was used for this (and probably poor handling along the way). For the purposes of what I'm doing for now and the cost, it's fine, but not something to buy expecting to be OEM quality. I also found some of the holes for the trim were the wrong size (too small) and had to get drilled out. But the holes for the windshield washer nozzles were too large, although they stay in place.

Haven't driven the car yet, and my next track event is supposed to be in 2 weekends, so I'll see what I'm able to determine about cooling.

The race car has all sorts of cooler ducting on the underside which feeds the exhaust and they have about a 1/2" gurney. It can't be smooth. I has to hurt flow to work.

I'm not sure about the GTD street car.

Another avenue to look at is opening up the fender liner vents for the oil and trans coolers. Even on the 350/500's they seem small and restrictive compared to my wife's C8.

example here

TeeLew said:

The race car has all sorts of cooler ducting on the underside which feeds the exhaust and they have about a 1/2" gurney. It can't be smooth. I has to hurt flow to work.

I'm not sure about the GTD street car.

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It's really about creating a pressure differential between underwood and above the hood, but I think we're saying the same thing. The gurney I agree should help with that. I do think there should be improved airflow out of the hood vs. the small stock vent, but that's just based on looking at it and touching it, there may be some other things I'm missing.

When you say the race car, which one are you referring to?

Stan Whitney said:

Another avenue to look at is opening up the fender liner vents for the oil and trans coolers. Even on the 350/500's they seem small and restrictive compared to my wife's C8.

example here
View attachment 111128

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I do want to look at the fender area some more as well. I'll take a look at that at some point.

For now, my car is only being used for track days (i.e. doesn't matter what mods I do to it) but am overall trying to keep the mods simple and reversible with the intent of solving a problem. That'll change, but I'm not sure whether I'll move this car towards time trials or the like at some point and that may change what I'm allowed to do.

TheTed said:

When you say the race car, which one are you referring to?

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The GTD (GT3) race car vs. the GTD street car

TeeLew said:

The GTD (GT3) race car vs. the GTD street car

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I thought that's what you were referring to. Yes, that hood is very different altogether.

TheTed said:

It's really about creating a pressure differential between underhood and above the hood, but I think we're saying the same thing. The gurney I agree should help with that. I do think there should be improved airflow out of the hood vs. the small stock vent, but that's just based on looking at it and touching it, there may be some other things I'm missing.

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Ya, the stock vents are decoration.

Well, this whole conversation made me take another look at the GT-4 style hood offered by Anderson Composites and compare that with what data is available from Race Louvers. Seems like without some prominent gurney the cooling ability may not be as pronounced as one would have originally thought. It looks like they (Race Louvers) would like to test the GT-4 style hood, but I haven't seen where they have had the opportunity to do so.

Learn something new every day.

The advantage that the Race Louvers have is that they stand proud of the hood. They have the gurney. AJ Hartman has some really good tunnel work he's done in this regard. The things I've done complete support what he found.

TeeLew said:

The advantage that the Race Louvers have is that they stand proud of the hood. They have the gurney. AJ Hartman has some really good tunnel work he's done in this regard. The things I've done complete support what he found.

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If you have some links on relevant work, I'd be very interested in reading them.

I've spent some time looking over the Race Louvers reports, which I've find very good and thorough. This one:


Was on an SN95, but "similar" in that it had the mesh openings. I think this GTD copy is a bit better because of the slight lip ahead of it, but that still did show a (very slight) increase in downforce and airflow vs. stock. Much worse than the Race Louvers.

Since this hood was cheap enough, I could always make some gurney flaps myself and rivet them on, and there is space behind the vents to install Race Louvers as well if I wanted to. However I'm not sure if that would be an "ideal" spot.

TheTed said:

If you have some links on relevant work, I'd be very interested in reading them.

I've spent some time looking over the Race Louvers reports, which I've find very good and thorough. This one:

https://racelouvers.com/content/Mustang-98-Hood-Extractor-Wind-Tunnel-Data.pdf

Was on an SN95, but "similar" in that it had the mesh openings. I think this GTD copy is a bit better because of the slight lip ahead of it, but that still did show a (very slight) increase in downforce and airflow vs. stock. Much worse than the Race Louvers.

Since this hood was cheap enough, I could always make some gurney flaps myself and rivet them on, and there is space behind the vents to install Race Louvers as well if I wanted to. However I'm not sure if that would be an "ideal" spot.

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Well, you already know your max temperature. You are heading to the track soon. Let's see how the hood does compared to the stock vented Dark Horse hood and whether it improves things, makes them worse, or no change.

Junkyard Dog said:

Well, you already know your max temperature. You are heading to the track soon. Let's see how the hood does compared to the stock vented Dark Horse hood and whether it improves things, makes them worse, or no change.

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That is my plan. We'll see how it goes.

TheTed said:

That is my plan. We'll see how it goes.

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Absolutely, there's no need to over-think it. If you want to play around, though, all you have to do is go to Home Depot and buy some 1/2 x 1 aluminum angle. Cut lengths that match the leading edge and tape them to the hood. Put some blue painters tape down first so you don't mess up the surface. I usually use gaffer tape to hold a gurney if I'm sticking it on something. Masking tape will work. Put one strip across the leading edge of the gurney and a couple small pieces on the back side to hold it down. Test the 1/2" side sticking up for a couple runs and the 1" side sticking up for a couple. Report if you can see a temp or feel a handling difference. For about $12, you can have several hours of innocent entertainment.

Once you figure out what you want for height, have some gurneys printed that exactly match the inner edge of your hood opening. You can paint them so they match and take them out or run them as you wish. These would probably run a couple hundred bucks to make, but they'd look good.