Air Box Design

[28rpu]

JD, Dan --
The Rule Book says "The body shall not be altered in height, width or contour . . ."

The Radiator Shell is a body part, right?  (It's not a mechanical part.)  And putting a hole in it certainly recontours it.
Stan

Using this logic a hole in the hood top is no different..huh : . Nick

[836dstr]

Thanks Jack !

I like your idea about the heat shields.

There is a new product out that fits under an air cleaner top that is scalloped (or radiused)  from a larger diameter at the top to smaller at the bottom and fits on the air cleaner stud. It purportedly aids in directing air into the carb.

This might work well with a closed plenum where intake air passes over the carb primaries and around the sides of plenum and stacks up at the back of the plenum and reverses direction back toward the carb.

It would be interesting to have a small wind tunnel where you could test various configurations.

Tom

[JackD]

The S+S side draft teardrop style has the type of peak feature you
 describe and has worked well for a long time in the center of a 1 barrel.
The drop center shape of the Moroso top complemented the shape of the base
and worked in a 4 B application.
NASCAR stuff has the same internal shape but a surround that takes air
 from the base of the windshield.

[dwarner]

"Using this logic a hole in the hood top is no different..huh  . Nick"

If you cannot see a hole in a plane view is that changing the contour?

DW

[interested bystander]

Having read and re-read the rulebook there is, imho, NO WAY you can have a hole in the grille shell and be legal for Street Roadster.

Taking the discusion in a slightly different direction, Jack D's hints on a properly countoured air cleaner base and top like NASCAR is obviously a power booster, disregarding how the air arrives there (scoop or under hood).  The K&N people among others have worked with some NASCAR teams on items like that.

One should isolate it from engine heat, though.

For port injected motors things become a little more difficult . but a properly designed plenum and an AIR FILTER in the right location will help with power.

It isn't by accident that people like K&N supply both Formula One and IRL with filters-both series port injected.

[JackD]

Hey, go easy with the speed secrets and let them discover it themselves. LOL
The cheap deal rather than an expensive K+N was to get 2 pedestrian type from Pep Boys and glue them together.
 Put them both in the system on top of each other.

[interested bystander]

Jack D- I'm flattered that you PERSONALLY responded to one of my posts.

You were no doubt in the Dago area far enough back  to remember the late Jim Ward-we could probably share a few tales- if your kidney and my prostate hold out long enough!

REX,

 Where are you with all this "Technical" discussion going on?
 Or are you waiting for all of us to make fools of ourselves?

[836dstr]

Jack,

I think that the question of plenum height has been answered. There have been other threads talking about hood scoop design and plenum volume.

The air intake question boils down to 3 options: 1) The duct through the grille shell, 2) A duct along the hood (like on the 357 car and others), or 3) A duct picking up air in back of the radiator.

The basic plenum design around the carburator would be pretty much the same. For now I will look at only last 2 options (although I do have a spare 'glass '32 grille shell on the shelf).

Using option #2, I can envision using a round duct with a bellmouth and simple radius lip. Because of the rake of the car, and the slight taper from the front to back of the hood, the outlet of the duct would be about 1/3 of the way back on the hood; whils laying flat on the grille shell top.

The link to the article on bellmouth design is very interesting !! You see a lot of rectangular scoop openings, most likely because of ease of fabrication. This article is an eye opener on air flow efficiency.

Using option #3 (air thru the radiator) the 3 problems I see are the proper duct or pick-up sizing to offset air resistance thru the fins and tubes; a more severe turn of the air up to the plenum; and the temprature increase of the air. Primary engine cooling is a 20 gallon water tank and electric water pump but the radiator is plumbed into the system. Any ideas on cooling the air? How about spraying Nitrous into air stream? JUST KIDDING !

Another question would be about air reversion at the back of the plenum, assuming a round back surface sealed to the hood. Would some type of air bleed system or port be helpful or detrimental?

Tom

[panic]

Just a BTW: the S+S side draft teardrop style was developed by Jerry Branch for the Harley-Davidson KR with Tillotsen carburetor about 1965, manufactured by Rick Bray under the Cy-Cal Products name in Long Beach. Web-Co had it in their catalog.

[jimmy six]

8-What fins?

[836dstr]

Hi JD,

In the air thru the radiator option, I was refering to the resistance and heat transfer of the radiator core, fins, vanes, what ever you want to call them.

Tom

[Rex Schimmer]

Tom,
Don't even think about taking the air through the radiator core, adde heat, potential inlet restrictions, not a good idea.

Here is another thought, looking at the rules it states that a street roadster may have a hood scoop per section 4.R which allows you to have a scoop up to 11 inches above the hood. It does not state that the scoop has to be on the center line of the hood, so how about centering the scoop in front of yourself and make its shape to help shroud you and your roll bar. You are already a big "blivit' on the frontal area of your roadster, use the air scoop to direct the air around you and not increase the frontal area of your car. The obvious thing that this brings is you have a scoop that doesn't contribute to additional frontal area, and it helps clean the air up going around you. The not so obvious things are that now you have an air plenmum that is sealed to your carb top that has huge volume and this will assist in reducing the air inlet speed to a minimum and recovering the maximum amount of pressure from the high velocity air that is coming into the inlet, i.e. "a little additional air pressure at the carb inlet never hurts!!!!"

Rex

[Dynoroom]

The rules do not say the radiator has to be used to cool the engine. They do not say what the fin count has to be. I could point out a truck that set two records this year at Bonneville that used the front grill opening to channel air that was cooled by a radiator (recirculating ice water) to a collection box that was then fed to the carburetor. Not the first and I'm sure it wont be the last, ask MacDonald, Eakers, McKinney, Fox, etc.

[836dstr]

Thanks guys !

The input is greatly appreciated ! Many things to think about.

An offset scoop (or bulge for a plenum) is an interesting idea. Good thing it's 6 months to the next El Mrage.

Circulating ice water to cool the intake air is also worth considering. The current radiator in the roadster has a 2" core and a large top tank. A single row core purpose build radiator is a definite way to go.

Thanks again,

Tom

[JackD]

With a small thermostat, you can further use the ice water that has
 soaked enough heat from the intake charge to no longer be useful for
that and add it to the block cooling system to work some more.
By the time you are done with those two stages the run will be over and
 you will have the hot water for coffee all around.