Absolute hood scoop final fix.

[ChipBeck]

Heath projects.

 

[LuLu]

Very clean install, looks great, Chip! But, I have my reservations on the "functional" option. Don't mean to sound negative, but if y'all opt for functional, you may be inviting (and nursing) other problems.

 

Gents...If you select functional, remember that this is a scoop...A real scoop in the true meaning of the word. It will scoop out all the debris flying in your air path and push that into your engine bay. This means everything airborne and my first concern would be getting caught in the rain (Yes, I will drive my SGT in the rain, and I have met about 100 other Mustang enthusiasts at ShelbyFest '08 in Hermann MO. who feel likewise).

 

Dumping rainwater on a hot aluminum engine will not be healthy for the engine. Also consider the effect of inducted moisture on your firewall mounted wiring harnesses? Those little pieces of factory tape sealing the harness are not waterproof.

 

Rain aside, if you are "engine bay anal", you just got a new full time job cleaning up the road dust, dirt, bugs, even trash your functional scoop scoops up. Anyone remember the "mailbox" scoop from AMC? That didn't last long (but neither did AMC).

 

Just look at your windshield after a road trip and imagine all that crap cooked on your cam covers, upper intake, headers, and strut tower brace? Y'all in Florida...How about those "love bugs"? Things get so bad down there, folks add window screens to their front girlles!

 

Right now here in Chicago, we are in our yearly "cottonwood" season, and ambient air is fully congested with our "summer snow". It's a PITA keeping this stuff off and out of any vehicle. It collects and clogs almost everything, even my home HVAC condensor has to be rinsed clean with with a garden hose, or, my HVAC shuts down. Likewise LuLu's radiator, or, LuLu overheats. Hell, you can't have a decent conversation with a neighbor without catching one in your mouth! Ahhh...I suppose every regional climate has it's own complications, eh? Just think about your local climate?

 

Keying off the crude (but effective) "tear drop" induction scoops of the mid '60s, "The General" learned something about this scoop stuff and developed "cowl induction". To this day, it's the single and only (IMHO) effective cold air system which boosts performance without causing additional complications.

 

I imagine myself sitting at the SGT design table, and I think Carrol Shelby understood this. If the SGT is indeed a tribute to the '66 GT 350, someone at that table understood that some things have to change because of lessons learned over the years. Thus, no functional scoop, but what we have in the new SGT looks sweet, and pays tribute.

 

Scooping up ambient air scoops up all that contaminates it and none of this "function" will reach back to benefit the SGT induction path. If y'all can tolerate the possible side-effects for style, go for it. Just be aware of what an open scoop will deliver to your engine bay. That said, the hood scoop fix Chip Beck has pioneered is awesome. Thanks, Chip!

 

Just my .02C, drive on, gents.

[cobrakalas427]

Chip - I think you and Heath have done an amazing job on a replacement scoop for the SGT and I'd love to have one myself. I also understand Mac's (LuLu) concern about the potential intake of foreign airborne matter with a functional scoop. My question to you is this...Do you think Heath or yourself could design some type of screen or scoop opening protection device that would address his concerns? Thanks again for all your hard work and investment to date...

[ChipBeck]

Chip - I think you and Heath have done an amazing job on a replacement scoop for the SGT and I'd love to have one myself. I also understand Mac's (LuLu) concern about the potential intake of foreign airborne matter with a functional scoop. My question to you is this...Do you think Heath or yourself could design some type of screen or scoop opening protection device that would address his concerns? Thanks again for all your hard work and investment to date...

 

Gentlemen,

 

A screen, or the black factory plastic block off plate, or nothing at all like the original ‘66 GT350 can be accommodated. But I believe, unless you use your Mustang in an area loaded with June bugs, or drive behind a lot of other cars on gravel roads, the screen is probably unnecessary. I have been caught out in the rain on two occasions in my aluminum bodied 427 S/C Cobra. Very little water entered the open hood scoop but quite a bit did enter the passenger compartment and me as I had no top for the car!! The completely exposed and unshielded Lucas electrics on the firewall of a Cobra make the plastic encased and taped up electrics under the hood of our Mustangs look like they're in a bank vault by comparison. I have been to many Cobra events and have talked to hundreds of Cobra owners. 95% of us have completely open scoops on our Cobras almost exactly like the one on my Shelby GT today. None of us have experienced the phenomenon of our hood scoops sucking up everything in our cars path and forcing debris into our engine compartments and causing damage to our engines by dumping cold rainwater on them. And I have never met a group of individuals more anal about their car engines than Cobra owners. (My Cobra engine, sitting directly underneath an open scoop, is pictured below) But heck, maybe I'm just unaware, so I put in a call yesterday to Gordon Levy who is one of the best-known Cobra mechanics in the nation (he rebuilt and maintained Dick Smith's famous #198 427 red competition Cobra) and over the last 20 years has worked on thousands of Cobras (mostly replicas but several genuine CSX cars as well) with open hood scoops. He told me that he is not aware of, has never seen, nor has he ever heard of an instance where this has been a problem. The closest thing to that I've seen he told me, is that occasionally on a track day where cars are following each other closely, at the end of the day one might find a few rubber marbles (from track tires) or a pebble or 2 in the turkey pan of someone's Cobra. These items did no damage and were simply tossed out. Small debris like dust tend to stay in the car’s airflow slipstream which passes above the top of a Cobras hood scoop as it is center mounted and flush to the hood just like our Shelby GT's. Next I put in a call to Shelby automobiles in Las Vegas and spoke to Tony who has been with them building Cobras with open hood scoops for almost a decade. He told me that in the nine years he has been with them producing Cobras they have never had one single complaint about the open scoops on the cars Shelby produces ingesting debris or water that caused a problem nor have they ever had an engine damaged in any way from anything that came through their cars open hood scoops. Ditto when I spoke to my local Superformance Cobra dealer.

 

At Shelby Automobiles, every car they are currently building, Super Snakes, GT500KRs, and CSX Cobras have functional hood scoops, but, because of its location, an open hood scoop on our Shelby GTs would act more like a heat and air extractor than an air intake.

 

I have learned from Mac’s posts and it's always interesting to hear what he has to say. The majority of Mac's concerns sound plausible and he does us all a service by raising them. But 40 years of experience with, and wind tunnel tests of, these open scoops should put any concerns to rest. It helps to understand the surface vehicle aerodynamics involved, the thermodynamics involved, and Shelby's reasoning for making the Shelby GT (&H) the ONLY vehicle they produce at Shelby Automobiles that does not have a functional hood scoop.

 

I'll keep this as brief as possible but this is still probably going to be a fairly lengthy thread. I use the term “functional” only to describe it as an “open scoop” if that is how the owner chooses to install it. But I have made it clear from the beginning of this thread, that because of its location, this hood scoop will not suck in air, contaminated or clean, and anything that does enter it must be heavy enough and must have been hurled with enough velocity by wind, or the car in front of you, or flying under its own power like a big June bug, to push it through the slipstream several inches above the top of the Shelby GT hood scoop. When in motion, the air pressure under our hoods is greater than the air pressure above the hood at the location of the scoop opening. The reasons for this, although not obvious, are not particularly hard to understand. But it does take a while to explain it.

 

In 1965 when Shelby built the first GT350 Mustang, he didn't have a wind tunnel and very little was known at that time about surface vehicle aerodynamics. Shelby reasoned that a scoop placed in the middle of the hood little more than 1 inch high and facing forward would literally scoop air into the engine compartment as it flowed over the top of the hood at high vehicle speeds (wind tunnel testing 2 years later showed he guessed wrong so he moved the scoops to the front of the hood in 1968). He did not seal that hood scoop to the top of the air cleaner but reasoned that the cooler air he believed would be scooped in might help performance. Shelby stayed with this center mounted forward facing scoop design from 1965 through 1967. In 1967 the Pontiac Firebird was introduced and offered with two forward facing hood scoops mounted in the center of the hood that WERE sealed to the top of the air cleaner in an attempt to increase manifold pressure at high vehicle speeds. Wind tunnel testing at speeds from 30 to 90 mph indicated that the effect of these functional scoops sealed to the top of the air cleaner was a decrease in manifold pressure instead of the expected increase. What was going on here? When a stream of smoke was viewed passing over the top of the car in the wind tunnel the answer became obvious. The center of a car hood is a low pressure area with turbulent air that often flows toward the front of the car at the hood surface. Because the air pressure under the hood, created by the large amount of air flowing through the huge radiator opening, is higher than the air pressure above the hood but below the slipstream that flows above the “center of a forward moving hood”, the center mounted forward facing scoops were actually sucking air out creating a partial vacuum instead of the desired higher pressure. Further wind tunnel testing revealed that the only area of an automobile hood where favorable air speed, pressure, and velocity, occurred (the technical term here is laminar flow) was from the leading edge of the hood to approximately 14 inches behind the leading edge of the hood. These aerodynamic discoverys resulted in a Shelby moving the hood scoops of GT350s and GT500s to the leading edge of the hood in 1968. In 1969 the first Trans Am had hood scoops on the leading edge of the hood as well, and the Camaro went to cowl induction at the rear of the hood. Even today, in order to make a modern Mustang hood scoop functional, Shelby has to place to scoop openings at the forward edge of the hood in this high pressure area in the front 12 inches of the hood. (Photo below) At the area of the hood behind this point the airflow detaches from the hood and flows four to 5 inches above it at high velocity and in a straight rearward direction until it smacks into the windshield about 4 inches above the windshield hood junction. Some of the air in the area beneath the main flow at the hood/windshield junction / swirls downward with the bottom of the eddy traveling toward the front of the car at fairly high speed and moderate pressure making the “cowl induction” that Mac described so efficient. I agree with Mac that in addition to cowl induction being efficient, its design prevents pebbles or large bugs from getting into it because although air can turn 180° quickly and easily, a pebble or large bug can not.

 

The air beneath the main flow above the center of the hood also swirls downward in a turbulent manner at very low speed and low pressure, most often toward the front of the car at the surface of the hood. This is the area where the Shelby GT hood scoop is located and the reason why it is totally ineffective in drawing air (or debris) into the engine compartment. It is more of an extractor than a scoop and would be more effective in this location flush mounted to the hood if it were turned rearword like the hood scoops of 1970 to 1979 Firebird Trans Ams. Most rain, dust, and small insects, are forced into the main air flow 4 inches above the Shelby GT hood scoop and they pass well over the top of it. The picture below, taken in Ford Motor Company's wind tunnel and provided by SVT clearly shows what I've just said. Air striking the front of the hood of our Mustangs flows along the surface of the hood for about 12 inches (laminar flow) at which point it detaches and flows four to 5 inches above the hood until it hits the windshield about one third of the way up where it reestablishes attached high pressure laminar flow which continues until the airflow detaches again about a foot behind the top of the windshield along the roof and does not reattach at any further point. Above the trunk of our cars the primary airflow is about 10 inches from the top of the trunk. All airflow below that is turbulent and low pressure. These surface vehicle aerodynamics are the reason that normally aspirated NHRA Pro Stock drag racers place their center hood mounted Scoops at least 4 inches above the surface of the hood (see photo below) and that Ford Racings FR500 Mustang requires a rear spoiler that is mounted 14 inches above the height of the trunk. Lifting the hood scoop and spoiler up high enough in these two examples places them into high-pressure and/or high velocity air so they can work as intended.

 

I've said many times that I am not an automobile expert, I just read a lot and I know some of the best automotive engineers in the business. But as regards dumping cold rainwater on a hot aluminum engine, here I have considerable experience. The small trickle of water that would make it through even an efficient automobile hood scoop would in no way damage the engine. Let me give you a few examples. The Good Guys car show here in Scottsdale every year showcases hundreds of hot rods that drive all over our town for the entire week. Many of them have no hood or cowling at all and are running aluminum engines that are completely exposed to the elements. They drive around in our occasional downpours with no concern for the health of their engines. I have driven my Jeep Rubicon across rivers completely submerging the bottom two thirds of its engine in the ice cold water of the river with no ill effect. Finally, the engine in my Glasair III aircraft has aluminum cylinders and an all aluminum case. On several occasions I have descended out of high altitudes and at maximum power settings. In these conditions my cylinder head temperatures read 425° and my exhaust gas temperatures are 1400°. I have flown into driving rain storms where the rain is just above freezing slamming massive amounts of ice cold water through the very efficient cowling scoop directly into the sides of the front two cylinders. Lycoming engine testing has shown that in such conditions, as the first raindrops hit the red hot cylinders they do cool those cylinders more effectively than air would but that even a heavy spray of water on the cylinders of a running engine cools them gradually enough to avoid any damage. A spray of water on an operating engine does not damage it akin to hurling a red hot non-operating engine block into a huge tank of ice cold water, which might damage it. At the Reno air races every year spectators can see a stream of water vapor behind the unlimited gold racers as during the course of one race over 200 gallons of cold water is sprayed directly over the cylinders and the oil radiators to help cool these engines that are running supercharger boost pressures 4 times what they were designed to handle.

 

Next, the windshield of our Mustangs is approximately 1640 square inches. Over 1000 square inches of that area is in high pressure laminar flow. The opening of our hood scoops is approximately 16 square inches, all of it in a low pressure, turbulent, non-laminar flow area. During a drive, the debris passing through this very inefficient open scoop would not be comparable to the debris on your windshield that is over 100 times the size of the scoop opening. Look at the picture of my Cobra below, it is Kirkham # KMP304, the scoop is completely open. Next is a picture of the engine and my Kirkham. It is true I don't drive the car all that much and unless I get caught out I do not drive it in the rain but the engine as you see it here has been driven with an open scoop over 2000 miles and almost 12 months since the last time that engine was detailed. My engine compartment is not packed with debris and the rainwater that has come through that scoop did not make it to the feeble Lucas electrics on the firewall nor did it damage my all aluminum Shelby American FE engine #CSX460.

 

Some of what Mac said is right on, a big love bug or beetle would have more than enough mass, like a race tire rubber marble or small stone, to blow right through the slipstream above the scoop and enter it. But even if it did, it wouldn't hurt anything.

 

Our cars already have a functional air cleaner scoop. The opening for our Ford Racing air filters is in the grill of our cars in a very high pressure area. It is far more efficient at pushing cold air into the area around the air filter than would be the stock hood mounted scoop ducted back to that same air cleaner. How long has it been since you've cleaned the aluminum area around your air cleaner? How much debris is in there? Is it filthy and packed with stuff? All of the contaminants and debris that are currently driven through your very efficient grille mounted air cleaner scoop that are not sucked through your air filter flow directly into your engine compartment now. The amount of debris driven into your engine compartment by your stock grille mounted air filter scoop, however much you have, is greater than the amount that will enter your engine compartment if you choose to open the scoop on your hood.

 

The bottom line is, screen, or plug, your hood scoop if you like, or don't use an open scoop at all because, as I have stated from the beginning of these threads, opening the scoop will not increase the performance of your car. Or follow Veronica’s advice and just leave the damn thing alone!! I just think it looks cool. And it does provide room for a modified strut tower brace that Heath and I are building that will clear the top of my now ordered Ford Racing Whipple Supercharger. Mac, I appreciate your positive comment on how the installation looks, I agree with some of your comments, and disagree with some. I'm just laying out this information as best I understand it. You and I will hook up soon enough, and when we do, the drinks are on me. You sound like an old Marine as am I, and if you're not, you should have been. Semper Fi.

 

Chip

 

[ChipBeck]

My Kirkham #KMP304 Cobras open hood scoop and a pretty clean engine. Note the cheesy Lucas electrics on the firewall.

 

[mrhugger]

I for one am glad he kept it brief! Steve

[AKSHELBY]

bump

[SGT/SC#0471]

Wow I think I am with Veronica on this after that explination...

 

Thanks for the info!

[fatboy]

My Kirkham #KMP304 Cobras open hood scoop and a pretty clean engine. Note the cheesy Lucas electrics on the firewall.

 

 

 

i want that Cobra. gimme

[zdle]

My Kirkham #KMP304 Cobras open hood scoop and a pretty clean engine. Note the cheesy Lucas electrics on the firewall.

 

Chip , just thinking if you knew where in front of the scoop the laminer flow starts to seperate form the hood?, could you put a vortex generator , or a gurney (very low height probably) there to get some air to tumble into the scoop ? just a thought , course then testing that would be the work part .............Zale

[69dejavue]

My Kirkham #KMP304 Cobras open hood scoop and a pretty clean engine. Note the cheesy Lucas electrics on the firewall.

 

 

 

Which reminds me. Why do the British drink warm beer? Refrigerators by Lucas Electric!

[69dejavue]

Gentlemen,

 

A screen, or the black factory plastic block off plate, or nothing at all like the original ‘66 GT350 can be accommodated. But I believe, unless you use your Mustang in an area loaded with June bugs, or drive behind a lot of other cars on gravel roads, the screen is probably unnecessary. I have been caught out in the rain on two occasions in my aluminum bodied 427 S/C Cobra. Very little water entered the open hood scoop but quite a bit did enter the passenger compartment and me as I had no top for the car!! The completely exposed and unshielded Lucas electrics on the firewall of a Cobra make the plastic encased and taped up electrics under the hood of our Mustangs look like they're in a bank vault by comparison. I have been to many Cobra events and have talked to hundreds of Cobra owners. 95% of us have completely open scoops on our Cobras almost exactly like the one on my Shelby GT today. None of us have experienced the phenomenon of our hood scoops sucking up everything in our cars path and forcing debris into our engine compartments and causing damage to our engines by dumping cold rainwater on them. And I have never met a group of individuals more anal about their car engines than Cobra owners. (My Cobra engine, sitting directly underneath an open scoop, is pictured below) But heck, maybe I'm just unaware, so I put in a call yesterday to Gordon Levy who is one of the best-known Cobra mechanics in the nation (he rebuilt and maintained Dick Smith's famous #198 427 red competition Cobra) and over the last 20 years has worked on thousands of Cobras (mostly replicas but several genuine CSX cars as well) with open hood scoops. He told me that he is not aware of, has never seen, nor has he ever heard of an instance where this has been a problem. The closest thing to that I've seen he told me, is that occasionally on a track day where cars are following each other closely, at the end of the day one might find a few rubber marbles (from track tires) or a pebble or 2 in the turkey pan of someone's Cobra. These items did no damage and were simply tossed out. Small debris like dust tend to stay in the car’s airflow slipstream which passes above the top of a Cobras hood scoop as it is center mounted and flush to the hood just like our Shelby GT's. Next I put in a call to Shelby automobiles in Las Vegas and spoke to Tony who has been with them building Cobras with open hood scoops for almost a decade. He told me that in the nine years he has been with them producing Cobras they have never had one single complaint about the open scoops on the cars Shelby produces ingesting debris or water that caused a problem nor have they ever had an engine damaged in any way from anything that came through their cars open hood scoops. Ditto when I spoke to my local Superformance Cobra dealer.

 

At Shelby Automobiles, every car they are currently building, Super Snakes, GT500KRs, and CSX Cobras have functional hood scoops, but, because of its location, an open hood scoop on our Shelby GTs would act more like a heat and air extractor than an air intake.

 

I have learned from Mac’s posts and it's always interesting to hear what he has to say. The majority of Mac's concerns sound plausible and he does us all a service by raising them. But 40 years of experience with, and wind tunnel tests of, these open scoops should put any concerns to rest. It helps to understand the surface vehicle aerodynamics involved, the thermodynamics involved, and Shelby's reasoning for making the Shelby GT (&H) the ONLY vehicle they produce at Shelby Automobiles that does not have a functional hood scoop.

 

I'll keep this as brief as possible but this is still probably going to be a fairly lengthy thread. I use the term “functional” only to describe it as an “open scoop” if that is how the owner chooses to install it. But I have made it clear from the beginning of this thread, that because of its location, this hood scoop will not suck in air, contaminated or clean, and anything that does enter it must be heavy enough and must have been hurled with enough velocity by wind, or the car in front of you, or flying under its own power like a big June bug, to push it through the slipstream several inches above the top of the Shelby GT hood scoop. When in motion, the air pressure under our hoods is greater than the air pressure above the hood at the location of the scoop opening. The reasons for this, although not obvious, are not particularly hard to understand. But it does take a while to explain it.

 

In 1965 when Shelby built the first GT350 Mustang, he didn't have a wind tunnel and very little was known at that time about surface vehicle aerodynamics. Shelby reasoned that a scoop placed in the middle of the hood little more than 1 inch high and facing forward would literally scoop air into the engine compartment as it flowed over the top of the hood at high vehicle speeds (wind tunnel testing 2 years later showed he guessed wrong so he moved the scoops to the front of the hood in 1968). He did not seal that hood scoop to the top of the air cleaner but reasoned that the cooler air he believed would be scooped in might help performance. Shelby stayed with this center mounted forward facing scoop design from 1965 through 1967. In 1967 the Pontiac Firebird was introduced and offered with two forward facing hood scoops mounted in the center of the hood that WERE sealed to the top of the air cleaner in an attempt to increase manifold pressure at high vehicle speeds. Wind tunnel testing at speeds from 30 to 90 mph indicated that the effect of these functional scoops sealed to the top of the air cleaner was a decrease in manifold pressure instead of the expected increase. What was going on here? When a stream of smoke was viewed passing over the top of the car in the wind tunnel the answer became obvious. The center of a car hood is a low pressure area with turbulent air that often flows toward the front of the car at the hood surface. Because the air pressure under the hood, created by the large amount of air flowing through the huge radiator opening, is higher than the air pressure above the hood but below the slipstream that flows above the “center of a forward moving hood”, the center mounted forward facing scoops were actually sucking air out creating a partial vacuum instead of the desired higher pressure. Further wind tunnel testing revealed that the only area of an automobile hood where favorable air speed, pressure, and velocity, occurred (the technical term here is laminar flow) was from the leading edge of the hood to approximately 14 inches behind the leading edge of the hood. These aerodynamic discoverys resulted in a Shelby moving the hood scoops of GT350s and GT500s to the leading edge of the hood in 1968. In 1969 the first Trans Am had hood scoops on the leading edge of the hood as well, and the Camaro went to cowl induction at the rear of the hood. Even today, in order to make a modern Mustang hood scoop functional, Shelby has to place to scoop openings at the forward edge of the hood in this high pressure area in the front 12 inches of the hood. (Photo below) At the area of the hood behind this point the airflow detaches from the hood and flows four to 5 inches above it at high velocity and in a straight rearward direction until it smacks into the windshield about 4 inches above the windshield hood junction. Some of the air in the area beneath the main flow at the hood/windshield junction / swirls downward with the bottom of the eddy traveling toward the front of the car at fairly high speed and moderate pressure making the “cowl induction” that Mac described so efficient. I agree with Mac that in addition to cowl induction being efficient, its design prevents pebbles or large bugs from getting into it because although air can turn 180° quickly and easily, a pebble or large bug can not.

 

The air beneath the main flow above the center of the hood also swirls downward in a turbulent manner at very low speed and low pressure, most often toward the front of the car at the surface of the hood. This is the area where the Shelby GT hood scoop is located and the reason why it is totally ineffective in drawing air (or debris) into the engine compartment. It is more of an extractor than a scoop and would be more effective in this location flush mounted to the hood if it were turned rearword like the hood scoops of 1970 to 1979 Firebird Trans Ams. Most rain, dust, and small insects, are forced into the main air flow 4 inches above the Shelby GT hood scoop and they pass well over the top of it. The picture below, taken in Ford Motor Company's wind tunnel and provided by SVT clearly shows what I've just said. Air striking the front of the hood of our Mustangs flows along the surface of the hood for about 12 inches (laminar flow) at which point it detaches and flows four to 5 inches above the hood until it hits the windshield about one third of the way up where it reestablishes attached high pressure laminar flow which continues until the airflow detaches again about a foot behind the top of the windshield along the roof and does not reattach at any further point. Above the trunk of our cars the primary airflow is about 10 inches from the top of the trunk. All airflow below that is turbulent and low pressure. These surface vehicle aerodynamics are the reason that normally aspirated NHRA Pro Stock drag racers place their center hood mounted Scoops at least 4 inches above the surface of the hood (see photo below) and that Ford Racings FR500 Mustang requires a rear spoiler that is mounted 14 inches above the height of the trunk. Lifting the hood scoop and spoiler up high enough in these two examples places them into high-pressure and/or high velocity air so they can work as intended.

 

I've said many times that I am not an automobile expert, I just read a lot and I know some of the best automotive engineers in the business. But as regards dumping cold rainwater on a hot aluminum engine, here I have considerable experience. The small trickle of water that would make it through even an efficient automobile hood scoop would in no way damage the engine. Let me give you a few examples. The Good Guys car show here in Scottsdale every year showcases hundreds of hot rods that drive all over our town for the entire week. Many of them have no hood or cowling at all and are running aluminum engines that are completely exposed to the elements. They drive around in our occasional downpours with no concern for the health of their engines. I have driven my Jeep Rubicon across rivers completely submerging the bottom two thirds of its engine in the ice cold water of the river with no ill effect. Finally, the engine in my Glasair III aircraft has aluminum cylinders and an all aluminum case. On several occasions I have descended out of high altitudes and at maximum power settings. In these conditions my cylinder head temperatures read 425° and my exhaust gas temperatures are 1400°. I have flown into driving rain storms where the rain is just above freezing slamming massive amounts of ice cold water through the very efficient cowling scoop directly into the sides of the front two cylinders. Lycoming engine testing has shown that in such conditions, as the first raindrops hit the red hot cylinders they do cool those cylinders more effectively than air would but that even a heavy spray of water on the cylinders of a running engine cools them gradually enough to avoid any damage. A spray of water on an operating engine does not damage it akin to hurling a red hot non-operating engine block into a huge tank of ice cold water, which might damage it. At the Reno air races every year spectators can see a stream of water vapor behind the unlimited gold racers as during the course of one race over 200 gallons of cold water is sprayed directly over the cylinders and the oil radiators to help cool these engines that are running supercharger boost pressures 4 times what they were designed to handle.

 

Next, the windshield of our Mustangs is approximately 1640 square inches. Over 1000 square inches of that area is in high pressure laminar flow. The opening of our hood scoops is approximately 16 square inches, all of it in a low pressure, turbulent, non-laminar flow area. During a drive, the debris passing through this very inefficient open scoop would not be comparable to the debris on your windshield that is over 100 times the size of the scoop opening. Look at the picture of my Cobra below, it is Kirkham # KMP304, the scoop is completely open. Next is a picture of the engine and my Kirkham. It is true I don't drive the car all that much and unless I get caught out I do not drive it in the rain but the engine as you see it here has been driven with an open scoop over 2000 miles and almost 12 months since the last time that engine was detailed. My engine compartment is not packed with debris and the rainwater that has come through that scoop did not make it to the feeble Lucas electrics on the firewall nor did it damage my all aluminum Shelby American FE engine #CSX460.

 

Some of what Mac said is right on, a big love bug or beetle would have more than enough mass, like a race tire rubber marble or small stone, to blow right through the slipstream above the scoop and enter it. But even if it did, it wouldn't hurt anything.

 

Our cars already have a functional air cleaner scoop. The opening for our Ford Racing air filters is in the grill of our cars in a very high pressure area. It is far more efficient at pushing cold air into the area around the air filter than would be the stock hood mounted scoop ducted back to that same air cleaner. How long has it been since you've cleaned the aluminum area around your air cleaner? How much debris is in there? Is it filthy and packed with stuff? All of the contaminants and debris that are currently driven through your very efficient grille mounted air cleaner scoop that are not sucked through your air filter flow directly into your engine compartment now. The amount of debris driven into your engine compartment by your stock grille mounted air filter scoop, however much you have, is greater than the amount that will enter your engine compartment if you choose to open the scoop on your hood.

 

The bottom line is, screen, or plug, your hood scoop if you like, or don't use an open scoop at all because, as I have stated from the beginning of these threads, opening the scoop will not increase the performance of your car. Or follow Veronica’s advice and just leave the damn thing alone!! I just think it looks cool. And it does provide room for a modified strut tower brace that Heath and I are building that will clear the top of my now ordered Ford Racing Whipple Supercharger. Mac, I appreciate your positive comment on how the installation looks, I agree with some of your comments, and disagree with some. I'm just laying out this information as best I understand it. You and I will hook up soon enough, and when we do, the drinks are on me. You sound like an old Marine as am I, and if you're not, you should have been. Semper Fi.

 

Chip

 

 

 

Chip; what about the old NACA duct style hood inlets?

[LuLu]

Chip; what about the old NACA duct style hood inlets?

You just HAD to copy the whole thread, didn't you. LOL!

 

BTW...Been meaning to ask you, 69, what's your CSM number?

 

I know you don't have your SGT in your possession at this time, but I've been wondering about that. You say so little about it? No mods yet? No seat time? Zup, my friend?

[69dejavue]

You just HAD to copy the whole thread, didn't you. LOL!

 

BTW...Been meaning to ask you, 69, what's your CSM number?

 

I know you don't have your SGT in your possession at this time, but I've been wondering about that. You say so little about it? No mods yet? No seat time? Zup, my friend?

 

Mac, I will PM.

[69dejavue]

Chip- just wondering about the efficiency of the Shaker Hood Scoop. That was also a low profile but claimed to have a ram effect and colder, more dense, air.

[FordRocks1]

Any updates from some of the folks that has purchased the heath scoop?

[ChipBeck]

Chip- just wondering about the efficiency of the Shaker Hood Scoop. That was also a low profile but claimed to have a ram effect and colder, more dense, air.

 

69,

 

As Mac pointed out some time ago, the only hood scoop farther back than about 12 inches beyond the leading edge of the hood that would be effective at all is cowl induction close to the base of the windshield and facing rearword. A shaker hood scoop facing forward in the middle of the hood is worthless. Wind tunnel tests show that any manufacturer claim of their effectiveness is misleading. Extensive wind tunnel tests led to Pontiac turning their hood scoop rearword on the 1970-1978 Firebird Trans Am as air close to the hood that far back is traveling toward the front of the car like eddies in a river close to the bank. Examine again the photographs contained in this thread, especially the one of the Mustang in the wind tunnel where the smoke clearly shows how the air separates from the hood about 12 inches rearword of the leading edge. The dynamic that causes this phenomenon is friction. No matter how aerodynamic the shape of any object is, as airflow pours over it, the airflow up against the surface of that object slows as it encounters friction from that surface. As the air immediately adjacent to the surface slows, the faster air behind the slowing air is forced up over the top of it to get around. The faster air flowing over the top of the slower air that has been bogged down by surface friction causes an eddy or whirlwind. If you've ever gone tubing down a river you have experienced this phenomenon. While you're in the middle of the river you're flowing downstream at a good rate. But when you get close to the bank you slow down considerably and often find yourself flowing back upstream as you are caught in an eddy. Surface vehicle aerodynamics are well known today and have been studied extensively in wind tunnels. Look at the functional hood scoops on modern cars. They are all at the leading edge of the hood (the new Camaro, Shelby KR, Shelby Super Snake, Cooper Mini, late-model Trans Ams, etc.) unless the manufacturer is trying to achieve a retro look (our Shelby GTs, Dodge Challenger, Saleen Parnelli Jones Mustang, etc.). The forward facing a shaker hood scoop like the one used on a Saleen Parnelli Jones Mustang is a cosmetic item and nothing else. There is no high-pressure or high velocity air at that scoops opening. When I get a chance I will post a photograph of the opening of my hood scoop with loose paper strips covering the opening so that you can see the airflow at speed. While the scoop facilitates some airflow that may keep my supercharger cooler, the airflow is as often out of the scoop at speed as it is in.

 

The hood scoops on Shelby Mustangs from 1965 to 1967 were in the middle of the hood facing forward because the carburetor was in the middle of the hood and nobody understood at that time that a scoop was ineffective there. In 1968, because of wind tunnel testing, the hood scoops were moved to the leading edge of the hood where they were effective. To achieve the retro look of the 1966 Shelby Mustang, Shelby Automobiles mounted our hood scoops in the same location they were mounted in 1966. For the same reason they weren't effective in 1966, they can't be made truly functional today.

 

Chip

[FordRocks1]

All I have to say is that if Subaru is making the scoop functional I see no need to worry with a functional scoop on our SGT. I see STIs running around from the 04/05 hard and have no issues with things getting in their engine bay from water,bugs or debris.Furthermore they are still making WRX and STI with functional scoops so obviously something is right and they are benefiting from it granted I know they are TC and they need the scoop to breath better.

 

[ilmor]

All I have to say is that if Subaru is making the scoop functional I see no need to worry with a functional scoop on our SGT. I see STIs running around from the 04/05 hard and have no issues with things getting in their engine bay from water,bugs or debris.Furthermore they are still making WRX and STI with functional scoops so obviously something is right and they are benefiting from it granted I know they are TC and they need the scoop to breath better.

 

 

I think their "scoop" is really for purposes of providing cool air to the intercooler, is it not?

[FordRocks1]

I think their "scoop" is really for purposes of providing cool air to the intercooler, is it not?

 

 

Yes it is because their intercooler sits on top of the engine....

 

[ChipBeck]

All I have to say is that if Subaru is making the scoop functional I see no need to worry with a functional scoop on our SGT. I see STIs running around from the 04/05 hard and have no issues with things getting in their engine bay from water,bugs or debris.Furthermore they are still making WRX and STI with functional scoops so obviously something is right and they are benefiting from it granted I know they are TC and they need the scoop to breath better.

 

FordRocks1,

 

For the purposes of this thread I am defining the term "functional hood scoop" as a scoop that is simply open to the engine compartment. A truly functional hood scoop would be plummed directly into a sealed air intake system and would provide enough ram air to raise manifold pressure at reasonable vehicle speeds.

 

I have driven my Shelby GT for over 2000 miles now with an open hood scoop. It has allowed little if any debris into the engine compartment. I have driven my Shelby Cobra for several years now with an almost identical open hood scoop, again, with an imperceptible amount of anything entering that scoop. I have had no problems with water, bugs, or debris, fouling my engine compartment as a result of my open scoop.

 

To address the last line of your post, there are three potential benefits from a hood scoop. The best hood scoops excel in all three areas. Those three benefits are.....

 

1. To raise the manifold pressure of a normally aspirated engine at practical vehicle speeds above what the manifold pressure would be without the hood scoop.

 

2. To provide any engine, (normally aspirated, turbocharged, or supercharged) with lower temperature (denser) intake air from outside the hot engine compartment.

 

3. Cosmetic reasons (they look cool).

 

The practical benefit of a hood scoop on a forced induction car like the Subaru is # 2, to pull cooler, denser air from outside the engine compartment and # 3 (it looks good). # 1 does not come into play on this Subaru.

 

On a normally aspirated car like our Shelby GTs, the forward facing, center hood mounted scoop can only provide # 3. It looks good, and, IMO, it looks a whole lot better when it's open. The black plastic block off plate screams phony. That scoop was open into the engine compartment on the 65 and 66 GT350, it's open into the engine compartment on Shelby Cobras, and although it provides no performance benefit, it looks genuine when it's open into the engine compartment on the Shelby GT.

 

Chip

 

[Chill]

Wow, this is great Chip. You and Heath are to be congratulated. Many thanks for all you two have done. When I replace the stripes (with paint) I'll be using one of your scoops.

 

Thanks again!

 

Chuck

[FordRocks1]

Chip,

 

Thanks for the explanation and yes I too would like to have one of your scoops, I am just waiting for the right time to purchase one for I what I've read it is not cheap but way cheaper than another hood.

I also think it is cool as hell to have it open, it looks more solid.

Chip, do you know how many people have actually bought this and is the person still making them?

 

Thanks,

 

Chris

[ilmor]

FordRocks1,

 

For the purposes of this thread I am defining the term "functional hood scoop" as a scoop that is simply open to the engine compartment. A truly functional hood scoop would be plummed directly into a sealed air intake system and would provide enough ram air to raise manifold pressure at reasonable vehicle speeds.

 

I have driven my Shelby GT for over 2000 miles now with an open hood scoop. It has allowed little if any debris into the engine compartment. I have driven my Shelby Cobra for several years now with an almost identical open hood scoop, again, with an imperceptible amount of anything entering that scoop. I have had no problems with water, bugs, or debris, fouling my engine compartment as a result of my open scoop.

 

To address the last line of your post, there are three potential benefits from a hood scoop. The best hood scoops excel in all three areas. Those three benefits are.....

 

1. To raise the manifold pressure of a normally aspirated engine at practical vehicle speeds above what the manifold pressure would be without the hood scoop.

 

2. To provide any engine, (normally aspirated, turbocharged, or supercharged) with lower temperature (denser) intake air from outside the hot engine compartment.

 

3. Cosmetic reasons (they look cool).

 

The practical benefit of a hood scoop on a forced induction car like the Subaru is # 2, to pull cooler, denser air from outside the engine compartment and # 3 (it looks good). # 1 does not come into play on this Subaru.

 

On a normally aspirated car like our Shelby GTs, the forward facing, center hood mounted scoop can only provide # 3. It looks good, and, IMO, it looks a whole lot better when it's open. The black plastic block off plate screams phony. That scoop was open into the engine compartment on the 65 and 66 GT350, it's open into the engine compartment on Shelby Cobras, and although it provides no performance benefit, it looks genuine when it's open into the engine compartment on the Shelby GT.

 

Chip

 

 

Somebody didn't tell Ford Racing where to put the hood scoop on the new Cobra Jet!!

 

http://www.autoblog.com/2008/10/07/more-pi...00cj-cobra-jet/

[ChipBeck]

Somebody didn't tell Ford Racing where to put the hood scoop on the new Cobra Jet!!

 

Those are supercharged cars so the ambient air pressure in that scoop is fine. (like the Subaru WRX) If that scoop is open it would allow the supercharger to suck cooler air from outside the engine compartment.

 

Chip

[ilmor]

Those are supercharged cars so the ambient air pressure in that scoop is fine. (like the Subaru WRX) If that scoop is open it would allow the supercharger to suck cooler air from outside the engine compartment.

 

Chip

 

Ahhh, I see! Thanks.

[mrichards]

Chip - I found the thread finally You have provided a great wealth of info to fellow owners. THANK YOU!!!!

I'll send a PM to get on the list for the right solution.

 

Any news on what SAI is offering for the warrantee replacement these days? I've seen no response from SAI in many weeks.

[ChipBeck]

Gentlemen,

 

I was out at Falcon Field in Mesa, Arizona today to get my Glasair III ready for a flight. I talked to Heath while I was there and he showed me five hood scoops he was shipping out shortly. Having now built several he appears to have it down to a real science and I can honestly say that these five examples are all nicer than the one on my car. I liked them so much that I intend to have another one built to put away in a box in case my car is ever involved in an accident. Veronica thinks I have lost my mind. I told her to count her blessings. A lot of other guys mess around with whiskey and women, so she shouldn't complain too much about my gasoline and cars!!

 

In any event, I conned him out of one to take home for a day to photograph. It may not look that impressive in dull white primer and without the mounting holes drilled, but when you hold it in your hands, it's an absolute work of art! Hard as a rock, slightly flexible like a very stiff fiberglass fishing rod, and able to withstand 400° indefinitely without warping. What you see here on my dining room table will soon be painted, polished, and adorning the hood, of a Team Shelby member. Cheers!

 

Chip

 

[JeffIsHereToo]

Gentlemen,

 

I was out at Falcon Field in Mesa, Arizona today to get my Glasair III ready for a flight. I talked to Heath while I was there and he showed me five hood scoops he was shipping out shortly. Having now built several he appears to have it down to a real science and I can honestly say that these five examples are all nicer than the one on my car. I liked them so much that I intend to have another one built to put away in a box in case my car is ever involved in an accident. Veronica thinks I have lost my mind. I told her to count her blessings. A lot of other guys mess around with whiskey and women, so she shouldn't complain too much about my gasoline and cars!!

 

In any event, I conned him out of one to take home for a day to photograph. It may not look that impressive in dull white primer and without the mounting holes drilled, but when you hold it in your hands, it's an absolute work of art! Hard as a rock, slightly flexible like a very stiff fiberglass fishing rod, and able to withstand 400° indefinitely without warping. What you see here on my dining room table will soon be painted, polished, and adorning the hood, of a Team Shelby member. Cheers!

 

Chip

 

VERY nice!

[SWEDEMAN]

Gentlemen,

 

I was out at Falcon Field in Mesa, Arizona today to get my Glasair III ready for a flight. I talked to Heath while I was there and he showed me five hood scoops he was shipping out shortly. Having now built several he appears to have it down to a real science and I can honestly say that these five examples are all nicer than the one on my car. I liked them so much that I intend to have another one built to put away in a box in case my car is ever involved in an accident. Veronica thinks I have lost my mind. I told her to count her blessings. A lot of other guys mess around with whiskey and women, so she shouldn't complain too much about my gasoline and cars!!

 

In any event, I conned him out of one to take home for a day to photograph. It may not look that impressive in dull white primer and without the mounting holes drilled, but when you hold it in your hands, it's an absolute work of art! Hard as a rock, slightly flexible like a very stiff fiberglass fishing rod, and able to withstand 400° indefinitely without warping. What you see here on my dining room table will soon be painted, polished, and adorning the hood, of a Team Shelby member. Cheers!

 

Chip

 

 

 

SAI needs to take a hint...do it right by getting the right people to do it!

Nice scoop.