SS cowl induction hood modifications for functionality

[bjhines]

I have been prepping the fiberglass SS scooped hood for modifications to make it a true cowl induction system. This is keeping in mind that allowing air into the engine compartment will cause cooling problems with the radiator(as well as aerodynamic problems).

 

The hood has a plate mounted to provide a flat sealing surface. the aircleaner's base-plate will be extended(like a tray) to seal against the bottom of the hood plate. The aircleaner sticks up through a hole in the hood plate to allow high pressure/fresh air to enter the carby but not the underhood area.

 

 

 

 

The aircleaner of choice. I can get shorter 14" elements if I want. 14" Edlebrock drop base, ~$30 from AutoZone.

 

 

 

This is the flat plate made of Alumalite sign board material. Available from most any sign shop in multiple colors(on one side)

 

 

 

Here is how they interface. This is without the lower tray mounted to the aircleaner baseplate.

 

 

Pass-Thru... Not really due to high pressure at the rear inlet and insignificant airflow into the carby for a true "duct"

 

 

 

 

rear inlet...

 

 

 

The plate is nearly level with the aircleaner. The aircleaner is 14" the plate opening is 18". You can see the passenger side offset of the engine from the offset hole. I also filled the rear hood stiffening channel with thin guage aluminum sheet for a cleaner rear inlet. I will screen the inlets to block the view inside(and keep vermin from nesting in there).

 

The tray is not done yet. I could just make a boxed tray.... or I could make a round fiberglass tray from the bottom of a plastic container. I intend to use foam or a bulb seal to allow for engine movement.

[deja]

Pretty cool. Much like the ram-air used in the late 60s and early 70s. My '70 AMX had one very similar with the addition of a vacuum activated door that would open the hood scoop during full throttle. I removed that door so the engine would always get cooler air. One funny thing, doing about 90 on the freeway I hit a bird, feathers went everywhere. When I arrived home I popped the hood to check the oil and discovered a bird head sitting in the pan that surrounded the air cleaner. Apparently he was decapitated during the 90 mph hit.

[Bartman]

Just curious on how this will work aerodynamically. I understand cowl induction and ram air, but what you posted looks like a combination of both.

 

I would think that air would flow through, so you will get nice cold air from that...but wouldn't that air flowing through prevent any 'cowl induction' flow?

[TravRMK]

That looks sweet! Looks like a K&N filter lid would also help since you have some room between the lid, and the hood.

[280Zone]

Obviously a square or rectangular enclosure will be easier to fabricate but it seems a round enclusure would benefit air flow. I also like the idea of the K&N filter air cleaner lid.

[SHO-Z]

From my understanding a true cowl induction has a sealed air filter with air coming in only cowl area only. NASCA uses cowl induction on their cars to use the high pressure area at the base of the window. I did a calc for one of the guys I work with who drag races a 67 Z28 and came out with about a 10 hp gain at 100 MPH on his 302. One of the options on the old Z28 was a cowl induction that fed thru the vent at the base of the windshield.

Your system will have a HP gain due to colder air. It is still a great job that you are doing.

[bjhines]

SHO-Z, There is going to be a pan from the bottom of the aircleaner baseplate to meet the hood plate.

 

In my opinion the carby does not flow enough air for any of this to act like a free-flowing duct. You can't really think of that NACA-style front duct as anything but a hole with stalled(high pressure) air in front of it. Air will not flow through the 2 ducts from front to rear as it would seem. There is a LOT of pressure over a large inlet area at the rear that is stopping flow through.

 

The windshield stagnation point(high pressure) will still be as effective as ever. The additional front facing NACA-style inlet will also have a stagnation point(high pressure) at the inlet.

 

The front inlet is smaller than the rear. The pressure should be similar at each inlet. If anything... I would guess that air will actually be forced OUT of the front inlet. In any case they are BOTH high pressure zones. They will only add to the positive pressure until one or the other is overcome.

 

There will be a rain/gravel shield inside the front inlet(shaped like a V). There are also going to be rain drains in the carby pan with restricted drain grommets.

Keep in mind that water/stuff has a lot of mass. It's own inertia will keep it out of the rear inlet. The front inlet will get it's inlet area's worth of oncomming debris.