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Air intake mod on 258?

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Gelalthedamned View Drop Down
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    Posted: Jul/03/2019 at 12:27am

So, Pierce Manifolds makes a plenum hat for the Weber 38/38.
 This means I could potentially build an air box to fit in the wiper fluid delete spot I got that Godzilla horn and headlight relays sitting, or I could cut a hole beside the headlight and have a filter behind the grill...or I could cut a hole in my hood and make a ram air scoop.
 Routing a short ram over the valve cover to the distributor side of the motor seems to be a waste of effort I think.

 what’s the worst that could happen...zero hp gains?

What would you do, if you weren’t even kinda concerned about stock...because it’s not stock and any excuse to get to go faster is a good idea?
Calamity - 73 Gremlin X zombie rod (daily driver)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 83GT Quote  Post ReplyReply Direct Link To This Post Posted: Jul/03/2019 at 5:32am
Go for the Ram Air...I just Love Hood Scoops.....Wink
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tyrodtom Quote  Post ReplyReply Direct Link To This Post Posted: Jul/03/2019 at 7:06am
The problem with hood scoops is unless they're really high, or placed very close to the front,  they're in a negative pressure area,  and won't get any ram pressure.

The airflow hits the front of the hood,  on most cars,  and is deflected upward away from the surface of the hood,  doesn't start to follow the body contours again until about the windshield region.

I did some tuft-test on a 79 Camaro circle track car years ago,   we studied the airflow around the body to see the most effective spoilers,  and if or not it was best to have a back window or not.

A tuft-test is short pieces of twine taped to the car body that indicates what the airflow is doing.
Aircraft designers still do it.

We did it to the front of the car too,   and that was  on a 79 Camaro body,   but each car is going to have it's own characteristics.

Plus, don't forget most state DMV laws frown on high hood scoops.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Jul/03/2019 at 9:06am
Use the factory air opening next to the radiator and let the air get to the intake through the very front.....

I was aiming that way but decided this was good enough......
I moved the windshield washer bottle back, made brackets to hold it straight. I found a coolant recovery bottle that was tall and skinny and fit around the AMC AC stuff. 


The yellow arrow shows where AMC had the cold air coming into the stock air filter snorkel - I built sort of an air dam at the bottom of the filter box I used so that air coming in through this area would be sort of re-directed to the bottom of the air box where the air enters before going through the filter inside.






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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gelalthedamned Quote  Post ReplyReply Direct Link To This Post Posted: Jul/03/2019 at 9:55am
Good lord man
You got all kinds of stuff in that bay
Calamity - 73 Gremlin X zombie rod (daily driver)
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Gelalthedamned View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gelalthedamned Quote  Post ReplyReply Direct Link To This Post Posted: Jul/03/2019 at 10:04am

Know what I don’t have?
That hole 

 But I can make one!

*i’m thinking boxed filter there is the way to go
With a tunnel feed into it from that spot I cut out on the top there

-I drive through mud every day
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Post Options Post Options   Thanks (1) Thanks(1)   Quote tomj Quote  Post ReplyReply Direct Link To This Post Posted: Jul/07/2019 at 11:02pm
at some risk of starting a religious argument...

below 0.3 mach, about 230 mph, air is basically incompressible. a very well designed scoop at 230 mph can produce up to couple percent pressure increase. at low speeds it's like holding a cup out the window; the air simply spills around the obstacle.

i think the main reason they appear on cars to to get at cooler air. i mean besides for how they look.

inserting a filter in a scoop would negate any pressure increase, even at mach 0.3.

a lot of NASCAR cars pick air up from the little grille under the wipers (cabin air intake) i think mainly because air tends to pile up at the windshield, and "probably" there at least isn't stalled air or low pressure there. no one wants to chop their car up for that!


NASA should be fairly credible in this department: https://www.grc.nasa.gov/www/k-12/airplane/machrole.html

"As an aircraft moves through the air, the air molecules near the aircraft are disturbed and move around the aircraft. If the aircraft passes at a low speed, typically less than 250 mph, it is observed that the density of the air remains constant."


i wonder too, just how much denser cool air is, actually, than warm air. as in molecules of oxygen per unit volume. the math is classically straightforward, not that i know it at all! lol.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gelalthedamned Quote  Post ReplyReply Direct Link To This Post Posted: Jul/07/2019 at 11:33pm
 
 Know how there’s kind of a scoop design on the hood of the 73 Gremlin?
Calamity - 73 Gremlin X zombie rod (daily driver)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gelalthedamned Quote  Post ReplyReply Direct Link To This Post Posted: Jul/07/2019 at 11:41pm
 I made a mock-up for how I’m gonna cut that.. and have a butterfly tied to my throttle position...mostly for just to be wtf.
 The ducting under the hood will be a little tricky, but it’s basically just an elbow dump into my shoddy cold air box.
 Give me a week or so, and I’ll take pics of the finished mod-wreck.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gelalthedamned Quote  Post ReplyReply Direct Link To This Post Posted: Jul/09/2019 at 8:54pm
You don’t care but, this first part should be in the rants and raves section- the plenum base I got didn’t even kinda fit over the top butterfly section. But with an hours worth of hand filing, it now slips down to the bottom ...with a few taps around the edges.
 Guess how many of my attaching bolt holes lined up with the carburetors holes? 2 & 1/2.
 This is on the back burner till I find my dremel.

In the meantime, my constant vacuum from the intake header got relocated from my pcv and now runs into the charcoal canister. (That thing is going inside the airbox too)
 My idle speed increased X300. What’s that about?

Rumor has it that you can increase density by length of pipe. 
Pressure and volume are separate from that and are dictated by diameter and velocity (velocity can be augmented by diameter too...less than 15degree transitions between stepped sizes is the magic #)
  temperature has too many variables, but if I had an air conditioner in this car...i’d so be running a duct from that thing into the airbox 
Calamity - 73 Gremlin X zombie rod (daily driver)
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