Carb to Hood clearance ?

pics gone

that is definetly a sweet idea..... i need to see if i can lay my radiator down or just move it lower

thxs guys

Nick, if your scoop goes right to the w/s you aren't getting any air from there. There needs to be a gap for the air to enter.

On my cowl hood, I can see leaves and things flying into the scoop even at a fairly low speed. I have a hole cut that fits close to the air cleaner.

Unless you have a pan made, your not getting any air forced in there, your just gaining hood clearance.

Bill

well i started designing my own scoop , i will keep everyone updated with the progress ........

Not so sure how much that will help..............be sure you put some sort of screen over the cabr now as all the rocks and stuff can get slung in there...............

Nick here is the one Rick and me built for his after he put the 2 4s on it

richter69 wrote:Not so sure how much that will help....

Jon makes a good point.

That proposed opening size (although decently wide) might not be tall enough IF the air approaching it (running up the curved cowl) creates a tumbling boundary layer of at the opening forcing the bulk of the rest of the air up-over the top of the opening. If the top of the new opening stays where it's at you might have to lower the bottom side of the opening down into the cowl surface to increase the height of the opening (without increasing the height of the scoop it's self).

69F100 wrote:Nick here is the one Rick and me built for his after he put the 2 4s on it

I think a scoop kinda like the svo mustang had would look good on a cal hood.

You can make a "plug" out of expanding foam and cardboard and sand it to your desired "shape" to fit the hole you cut in your hood and then build a fiberglass mold of the plug to lay out your scoop in.

That way you can make a flange to fiberglass it too your hood from the bottom side and it will fit your hole tightly.

That's a good idea Randy

im sure i can double the opening (height) if i notch the hood in the other direction ....just tring to achive a clean look also ...... but i guess i can achive the look of the svo hood if i give it a "v" shape

almost like the inset on these factory hoods

Nick, what about grafting a Boss9 scoop to blend in with the cowl hood. Maybe keep the slope of the cowl, slide the Boss 9 scoop forward slightly to create the recess you are talking about. Just a thought.

Travis

+++++++Guess I should have started back a page, looks like thats what you are tryig to do +++++++++++++

If you are using an air pan, is there any reason not to add a scoop to the side of your cowl hood... kind of like what the Grabber Mavericks/Comet GTs did in the early 70s...?
http://we-insurance.changeip.net/media/2009/07/2009072709410864.jpg

DILLIGASDAVE wrote:you might have to lower the bottom side of the opening down into the cowl surface

Something like one of these.

richter69 wrote:Not so sure how much that will help..............be sure you put some sort of screen over the cabr now as all the rocks and stuff can get slung in there...............

its gotta do more good for the carb then the way it sits now .....i would think ..........

thanks Dave ...i was trying to do that with photobucket .....

Im selling my hood and harwood scoop if your interested.

How about this idea a 5-7" tall Pro-Stock hood scoop with a Cobra type turkey pan.

i found this formula on www.landracing.com

Here we GO!
The underlying question of sizing a scoop is how small can I make it and still feed the engine. Smallness is required because drag becomes prominent when speeds go up and air spills around the scoop opening because it is larger than needs to be. This added drag reduces the top speed of the vehicle. The foundation equation is not difficult and is easily solved.

EQUATIONS


CFM = (Displacement (cubic inches) * Volumetric Efficiency * RPM) / ( Speed (mph) * 2 * 1728 * 60 * 1.467)

CFM(cubic feet per minute) is not a useful parameter in scoop size although it does give you an indication of how much air you are pumping and is a great starting plce for figuring carburetor (jeeze, did I spell that right?). Remember also that the volumetric efficiency is highest at the torque peak (I think!) and can in some instances be greater than 100% because of ram tuning. My advice is that unles you have something like Dyno 2000 which can give you a volumetric efficiency number for your engine parameters, then I humbly suggest that you use 90% or 0.9 in the equation. I also assume you all know how to determine the displacement of your engine? If not, email me and I'll tell you. Awww hell, it's Disp = number of cylinders times bore times bore times 0.7854 times stroke.


CFS = CFM / (60)

CFS (cubic feet per second) divided by the target speed in feet per second gives the scoop size in square feet.


Scoop size (sq ft) = CFS / (Speed (mph) * 1.467)

But let's convert this puppy to square inches by multiplying scoop size by 144 sq inches per sq ft.

Scoop Size (sq inches) = Scoop Size (sq ft) * 144 sq inches per sq ft

Now that wasn't too hard was it? But I will combine all the above and simplify so the math gets easier.


Scoop Size (sq inches) = 0.00047338 * ( Disp * Vol Eff * RPM) / Speed (mph)

EXAMPLE


How big does a scoop need to be to supply a 369 cubic inch engine with a vehicle target speed of 240 mph. Volumetric efficiency of the engine at 8000 rpm is 90%.


Plugging into the friendly formula and find....

Scoop Size (sq inches) = 0.00047338 * (369 * 0.9 * 8000) / 240 = 5.24 square inch opening for a motor at 8000 rpm and going 240 mph.


Now what size scoop opening is needed for the acceleration phase of the speed run? Lets try the same parameters at a speed of 100 mph, WOT, same efficiency...

Scoop Size (sq inches) = 0.00047338 * (369 * 0.9 * 8000) / 100 = 12.57 square inch opening for a motor at 8000 rpm and going 100 mph.


So you can see the problem with using this as gosphel. If you build a sealed air box with the high speed opening, then you will be starving the engine for air at any speed less that the target speed! This will cause the air density going into the engine to be decreased and while the cfm going into the engine may be the same, the mass of ais isn't. This may cause an over rich condition or may even lean out the engine because of poor metering signals for the fuel flow.


This has been a serious effort to try and determine how big a scoop needs to be to meet a given speed requirement while minimizing drag. During the analysis it was found that scoop size for a given speed and engine conditions can be deterined. but that this scoop size is inadequate for slower vehicle speeds at the same given rpm. As a get off the stage commentary, I would suggest that the very best air intake system can be found on the NASCAR Winston Cup cars: the inlet is at the base of the windshield and is a very large opening. Since it is in stagnant high pressure air, ne penality is for drag is observed, plus you get a bit of a boost! I would futher comment that the scoops which have the opening against the glass but which are also very tall and further insulting the air flow problem because the high speed air over the top of the scoop is actually sucking the air from the scoop, not the other way around. Point that puppy into the wind, boys! If you use this or a similar technique or the same methodology, just remember, your milage may vary :^}.


I have been investigating the use of some 2D Computational Fluid Dynamics programs to visualize the flow in a scoop. I have found one that looks interesting, but the freebie demo only has 31 x 31 nodes for the solution matrix. I can buy the full code which has 301 by 301 nodes for a mere 300 bucks...from Japan. Maybe, I dunno...

,,,,,,,,,or just buy a forward facing hoodscoop............damn it aint like your working on a space shuttle.

richter69 wrote:,,,,,,,,,or just buy a forward facing hoodscoop............damn it aint like your working on a space shuttle.

Reinventing the wheel...

I mean how close is it? will the damn hood not shut or what??

If you do a forward scoop get some wheelie bars and W tires................then that bitch will rock..................

here is my solution you can see it in the still shots in the video,i did not know how to get the still shots in to pictures.the car went over .200 quicker and for those who want to know its a 28x10.0 non W tire.


https://www.youtube.com/watch?v=2G39Rdhutnw

well here is the new hood scoop, we will jet up a couple and see how she likes it , before we spray her again

What scoop, j/k, looks great.