Carb to Hood clearance ?

so what is the minimun it should be .... from the vent tubes to the hood ? on a deal like mine were the cowl hood goes all the way to the windshield im i losing some hp ? and would i gaing any from going to a foward facing hood ?

ive also notice when im done with a pass to have red dye on top of the carb could i be have an reversion issue or turbulance issue with that hood ?


what do yall think

A properly sized and fitted forward facing scoop can be worth some et and mph over a cowl.

bruno wrote:so what is the minimun it should be .... from the vent tubes to the hood ? on a deal like mine were the cowl hood goes all the way to the windshield im i losing some hp ? and would i gaing any from going to a foward facing hood ?

ive also notice when im done with a pass to have red dye on top of the carb could i be have an reversion issue or turbulance issue with that hood ?


what do yall think

If your cowl does fit the windshield fairly tight, that is where it is going to pull the most air on a rear facing scoop. As far as clearance as long as you have enough that the vent tubes clear, you are OK. Do you have an air pan set up for the cowl??

richter69 wrote:A properly sized and fitted forward facing scoop can be worth some et and mph over a cowl.

I agree.

Also some gains in how the air is pulled into the carb over the airbleeds and such, you just have to tinker with it.

No Travis i dont have an air pan setup

Definatley worth the fab work. You will have to fatten the jetting a size or 2. I made this setup myself and sealed it off with armaflex pipe insulation. Only thing I wish I would have done is to have used an air bell at the carb entry.

Typically 3/4" above the vent does the job. The red dye is telling you that you have air blowing ACROSS the carb and thats a no-no.

Good luck. : )

Im going to ask a stupid question based on the pics and post Ive seen....

you asphalt guys dont run an air filter? Do you not have an issue with dirt/dust/rocks and etc making it into the engine? Does a standard K&N or similar rob that much horsepower to negate its use?

Obviously I cant get away without one but we are typically running the engine the same as most of you guys time wise just for a shorter distance and a little dirtier. Ive shied away from a pan because I dont want to chance water being trapped on top of the carb in a deep pit.

Regardless, Travis, what gauge aluminum is that?

Sorry to hyjack.

With a forward scoop I would run a cleaner or some sort of screen to keep the rocks out. Our tracks dont offer fully paved pits, so gravel and rocks will get in there from the front. I have had headlights busted out waiting behind a car in the burnout box. I have run with and without an aircleaner with no difference in et either way, so if you can fit a good sized filter in there its a no brainer.

IcallhimGeorge wrote:Im going to ask a stupid question based on the pics and post Ive seen....

you asphalt guys dont run an air filter? Do you not have an issue with dirt/dust/rocks and etc making it into the engine? Does a standard K&N or similar rob that much horsepower to negate its use?

Obviously I cant get away without one but we are typically running the engine the same as most of you guys time wise just for a shorter distance and a little dirtier. Ive shied away from a pan because I dont want to chance water being trapped on top of the carb in a deep pit.

Regardless, Travis, what gauge aluminum is that?

Sorry to hyjack.

I believe its a matter of having the room for an air cleaner. Like bruno was saying, I too have a clearance issue with my vent tubes being close to the cowl so theres no way an air cleaner is going on there

PRO SYSTEMS wrote:Typically 3/4" above the vent does the job. The red dye is telling you that you have air blowing ACROSS the carb and thats a no-no.

Good luck. : )

PRO SYSTEMS,

What would you do to cure this problem ?

Nick

Be sure you have a way for air to pile up and not blow through the neighborhood. Forward facing scoops and pans work almost everytime. Cowl hoods work half the time on a first effort and often require tweaking. If you add a cowl hood air pan and the carb doesn't require adding 1-2 jets..get back to work..you're not done.

IcallhimGeorge wrote:Im going to ask a stupid question based on the pics and post Ive seen....

you asphalt guys dont run an air filter? Do you not have an issue with dirt/dust/rocks and etc making it into the engine? Does a standard K&N or similar rob that much horsepower to negate its use?

Obviously I cant get away without one but we are typically running the engine the same as most of you guys time wise just for a shorter distance and a little dirtier. Ive shied away from a pan because I dont want to chance water being trapped on top of the carb in a deep pit.

Regardless, Travis, what gauge aluminum is that?

Sorry to hyjack.

I think I used .040. I really can't remember. I wanted it stiff enough not to buckle when you shut the hood, yet not be to rigid to put extra pressure on the hood.

thanks guys.

Hyjack over.

bruno wrote:so what is the minimun it should be .... from the vent tubes to the hood ? on a deal like mine were the cowl hood goes all the way to the windshield im i losing some hp ? and would i gaing any from going to a foward facing hood ?

ive also notice when im done with a pass to have red dye on top of the carb could i be have an reversion issue or turbulance issue with that hood ?


what do yall think

Nick, On my ole Maverick i ran the old thunderbolt style tubes from a home made pan. It picked the et up a full 1/10 over none at all

I've always heard that the windshield cowl hoods slowed a Mustang down a tenth. When I went from a pro-stock styled scoop to the 8" windshield cowl on mine ,it made absolutely no difference what so ever. It maybe because I've got the inner fenders cut out and it's getting air from there.I like the cowl better be cause of the inceased vision.

PRO SYSTEMS wrote:Be sure you have a way for air to pile up and not blow through the neighborhood. Forward facing scoops and pans work almost everytime. Cowl hoods work half the time on a first effort and often require tweaking. If you add a cowl hood air pan and the carb doesn't require adding 1-2 jets..get back to work..you're not done.

is that something you guys put in your design when yall do carbs ?? sounds like i need to desing an air pan

56Tbird wrote:I've always heard that the windshield cowl hoods slowed a Mustang down a tenth. When I went from a pro-stock styled scoop to the 8" windshield cowl on mine ,it made absolutely no difference what so ever. It maybe because I've got the inner fenders cut out and it's getting air from there.I like the cowl better be cause of the inceased vision.

i wonder if it would make a diff. at all when im on the spray ?

How many promod cars do you see with cowl hoods?

I'm sure that the promods need alot more air intake than our motors need.I'm sure at some point there's a big need for more air and helping it in the carbs with a pan or scoop is a must.

richter69 wrote:How many promod cars do you see with cowl hoods?

plenty , but most of them have a big ole hat sticking up through them sittin a top a big ole huffer

Carburetors are for lawn mowers and weedeaters anyway

Wide cowl scoops on P/M & T/S cars do give some more needed valve cover room on some body styles. Without the cowl scoop some of the PM/TS car bodies would have the valve covers poking through a flat hood line a decent amount.



In my opinion the problem with using a rear draw windshield cowl scoop on drag car is directly related to the increase in height of said scoop (& the increase of volume of the rear opening). The NASCAR stuff works because their pulling air directly at the base of the windshield/hood where the angle of the hood vs the angle of the windshield creates a high pressure boundry in a small area. But on a drag car as the cowl scoop gets taller & taller (and opening at the windshield gets bigger & bigger) you loose more & more of the high pressuer area at the base of the windshield. Use a tall enough cowl and you might find that the air rushing past the outside of the opening at the back of the scoop & up what's left of the windshield height can actually pull air volume out from inside the scoop instead of cramming air volume into the scoop.


The old P/S truck class from the late 90's is a perfect example of how a rear draw windshield cowl just really isn't an efficient scoop on a drag car. They quickly learned that pulling air from the back of the cowl at the windshield didn't work good enough and had to change the air pan/duct work inside the cowl so it ran forward to the front of the truck so they could pull air from the grill instead of back at the windshield.

Just because you run a cowl type hood does not mean you have to draw the air from the back. Actually a cowl hood can and will most likely be more aerodynamic than the forward facing scoops. I don't know how to post a picture from another site, but I will link you to it so you can see how others make it work. This car is a local racer who runs in the 4's to 5.00's in the eight a mile. It is also piloted by girl on problably one of the 20 worst tracks in the nation. It is a 1/4 mile facility but is kind of small and rough around the edges. Maybe one of you BIG TIRE guy's here can drag the pictures into this post, I am not smart enough for that.


http://members.boardhost.com/street-freaks/msg/1263602522.html


So Bruno, if you have a way to lay your radiator back a little at the top, You could make an airpan set up much like this and close the back off of the cowl hood all together. There are way to many cowl hood guy's out there that ARE making thier setup work. Take a look at the NMRA Hot Street class for instance. These N/A small blocks with a cubic inch limit of 440, weigh 3200, NO FORWARD FACING SCOOPS , 10.5 tires ( See other thread about this ) and are running as fast as 8.30's and 8.40's during the last race of the season. So get out in the garage and start fabbing. You will always have someone who will tell you that you should have done this or you should have done that, but try something for your self and learn from it. Hell I've built things 2 and 3 times just to get to where I want to be before it will work., there is no shame in doing it for yourself.

Travis

Travis those camaro pics are exactly what I'm talking about. They built their air pan inside the cowl so it faces forward and looks like it pulls air from the grill just like the Pro Stock trucks did in the late 90's.

If you guys with cowl scoops want to try something similar but don't feel you have the sheetmetal or 'glass skills, Jerry Haas does offer a forward facing PST style air pan on his web site that might work. It's at the bottom of the page.

http://www.jerryhaas.com/hoodscoops.html

DILLIGASDAVE wrote:The old P/S truck class from the late 90's is a perfect example of how a rear draw windshield cowl just really isn't an efficient scoop on a drag car. They quickly learned that pulling air from the back of the cowl at the windshield didn't work good enough and had to change the air pan/duct work inside the cowl so it ran forward to the front of the truck so they could pull air from the grill instead of back at the windshield.

Dave,
Sorry I missed the last sentence.I am temporarily laid off as you can see by my post count in the last few days. Ain't the internet a great place??

Travis