Cowl hood. Cowl induction

[javajoe79]

 So to any of you guys who have run one or know some good info about them please share what you know. I am building one currently and thinking of a few different options.
 
  First off I am considering making a radius at the back edge near the windshield. On top only or top and sides???

Also rather then a radius at the end, I am considering a rectangular opening on top of the cowl hood, near the back, with radiused edges.

 Now the rule states no closer then 2" to the windshield but is or can a bigger gap be better and why?   

 Engine is currently a single 1350 dominator C LSx Chevrolet with nitrous.

Thanks ahead of time.

[krusty]

     Research the NASCAR Cup cowl intake. Probably some info and pics online. A lot of fab and wind tunnel time has been spent developing this system. Used airboxes can be found online at Roush Yates used parts. Unfortunately, the base is sized for a Holley 4150, but R/Y has an aluminum drop base that fits an 1150 Dominator (I use it as a filter base on our LSR engines). The connection between the cowl and the box is the fussy part. IIRC, you want a nice tight radius on the forward edge of the inlet and a generous one on the rear.        vic

[Captthundarr]

Krusty is steering you in the right direction. Sealig it tight is a must to get the most effect. What's this going on?

Frank

[Cajun Kid]

Cup does what they do because that is all they can do !!!

If they could use a hood scoop or ram air , I am sure the motor builder would prefer that ?

Charles

[javajoe79]

This is on a 96 Sonoma. We had a big prostock style hood on it but now only one carb and we are trying to ditch some drag with just a cowl hood.

[krusty]

      If they could use a hood scoop or ram air , I am sure the motor builder would prefer that ?

   Charles:  How many drag horsepower is the hood scoop vs. the increase in engine horsepower (and at all speeds from, say, 140 mph to 200 mph) ?  While the engine tuner might like it, the crew chief might not.  Yes, it's true  that's what they have to do by the rules, but that doesn,t necessarily mean it's not the best for their program.     vic

[Cajun Kid]

Vic, yes I agree, my main point is the Motor and Motor Builder may prefer another method of induction and since the LSR Sonoma Truck in question does not have to follow "Cup" rules, then maybe there are alternatives  that can increase flow or ram to the carb box better than a "Cup style" cowl and not increase drag or at east have a fair trade off and not be as bad as the big honking pro stock snorkel ?

Just my .02 worth..

but what do I know, I am just a lonely one man operation !!!

[Hot Rod Lincoln]

So to any of you guys who have run one or know some good info about them please share what you know. I am building one currently and thinking of a few different options.
 
  First off I am considering making a radius at the back edge near the windshield. On top only or top and sides???

Also rather then a radius at the end, I am considering a rectangular opening on top of the cowl hood, near the back, with radiused edges.

Thanks ahead of time.

I don't know if this will help of not, but our hood scoop was made at the very last minute last year and ended up being 4" taller than we wanted and not as far back as we wanted. While we were doing "shakedown" runs on the salt I went to the store in Wendover and bought 2 packs of shoe laces. I cut the laces to about 8" and taped them inside the back of the hood scoop 4 strings and then 2 strings at the base of the windshield. It was kind of interesting running 150+ mph and looking at the stings going the same direction I was going. All 6 strings were being sucked into the back of the scoop very forcefully. Our scoop has sharp edges on it. I don't think you need to radius them, but I guess it would hurt.

Jon

[SPARKY]

Find the HR article on Turks Camaro---they did a good bit of scoop work----not much of a penalty if you choose right  with a forward facing pro stock type

[Captthundarr]

I've been considering cutting in a NACA duct into the front area of our 4"cowl hood just in front of the air filter area. Opions?

[tauruck]

 I don't know if what I say will help. Is the cowl there to clear manifold/carb height or to channel air to the airbox?. I used to do aero and airbox systems for a class called modified saloons here in SA. They were Trans Am style cars similar to the image. They used to have NASCAR style airboxes but I figured a snorkel system feeding two hoses to an enclosed airbox would direct good clean air straight to the carb. We're talking 1999. Two ducts in the front airdam with 4" flexible hoses running to the airbox. The airbox had oval snouts for hood clearance issues. The box itself had a ring built into the base to locate the tall K&N filter and a few small tweaks to get the air flowing. The lid also a Carbon piece had a further ring built into it. Any air that came in went straight through the filter. No bleeding whatsoever. My first version went out on a customer car and the older guy that owned/drove called me to say "This thing works!!!" not in those exact words. The design of the layout in the pit lane was much like the NASCAR ovals you have. The mechanic's highlight was to drive the car down the pit lane at the end of the day to get the car behind the wall. On this occasion he did it without the front bodywork on the car. The report that came back was that when he reached about 35mph the flexible hoses filled with air and kinda stood up. He said they were clear of the engine. The other guys saw it and by Monday morning my phone was ringing off the hook. The setup progressed to the point that I had molds to produce composite ducts that attached to both ends via silicon boots. No leaks. I found a very good material and poured my own boots from a tool that even had recesses built in for the clamps. If the rules allow ducting like I just described and you don't have manifold height problems I guarantee this system works. The faster you run the better.

[CTX-SLPR]

Just thinking about this (well something related anyway) with regards to induction.

While routing the air from the front of the vehicle has it's advantages as does the cowl hood if you need the clearance anyway.  What about converting what used to be heater plenum that pulled from the cowl panel and routing the air into the engine from there?  I'm guessing that due to the "fire through the cabin vent" restriction, almost everyone is not using the heater plenum anyway and it's definately higher pressure. 

Thanks,