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Air intake mod on 258?

Printed From: TheAMCForum.com
Category: The Garage
Forum Name: AMC 6 Cylinder Engine Repair and Modifications
Forum Description: AMC-made I-6 engine mechanical, ignition and fuel from basic repair to high-perf modifications
URL: http://theamcforum.com/forum/forum_posts.asp?TID=100821
Printed Date: Jan/23/2020 at 9:28pm


Topic: Air intake mod on 258?
Posted By: Gelalthedamned
Subject: Air intake mod on 258?
Date 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?


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Calamity - 73 Gremlin X zombie rod (daily driver)



Replies:
Posted By: 83GT
Date Posted: Jul/03/2019 at 5:32am
Go for the Ram Air...I just Love Hood Scoops.....Wink

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1983 Spirit GT 258 4-speed
2014 Star Stryker - Daily Ride


Posted By: tyrodtom
Date 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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66 American SW, 66 American 2dr, 82 J10, 70 Hornet, Pound, Va.


Posted By: billd
Date 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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Posted By: Gelalthedamned
Date Posted: Jul/03/2019 at 9:55am
Good lord man
You got all kinds of stuff in that bay


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Calamity - 73 Gremlin X zombie rod (daily driver)


Posted By: Gelalthedamned
Date 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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Calamity - 73 Gremlin X zombie rod (daily driver)


Posted By: tomj
Date 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!

wikipedia: https://en.wikipedia.org/wiki/Compressible_flow" rel="nofollow - https://en.wikipedia.org/wiki/Compressible_flow

NASA should be fairly credible in this department: https://www.grc.nasa.gov/www/k-12/airplane/machrole.html" rel="nofollow - 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 https://www.grc.nasa.gov/www/k-12/airplane/fluden.html" rel="nofollow - 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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1961 roadster american, 195.6 OHV, T5
1968 american, 199ci, T96
sr-ix.com



Posted By: Gelalthedamned
Date Posted: Jul/07/2019 at 11:33pm
 
 Know how there’s kind of a scoop design on the hood of the 73 Gremlin?


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Calamity - 73 Gremlin X zombie rod (daily driver)


Posted By: Gelalthedamned
Date 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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Calamity - 73 Gremlin X zombie rod (daily driver)


Posted By: Gelalthedamned
Date 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 


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Calamity - 73 Gremlin X zombie rod (daily driver)


Posted By: Gelalthedamned
Date Posted: Jul/11/2019 at 11:06pm
Guess which object I didn’t calculate the space for?
 *Make it fit*
-the horn is now in the forward section offender well 


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Calamity - 73 Gremlin X zombie rod (daily driver)


Posted By: billd
Date Posted: Jul/12/2019 at 7:42am
Originally posted by Gelalthedamned Gelalthedamned wrote:

Good lord man
You got all kinds of stuff in that bay


LOL - it's an Eagle. Two vacuum cans - one for the HVAC and such, another for the Select Drive system, PDC (Power Distribution Center), PCM (hidden under right hood hinge-  - oh THAT was fun!!), coolant recovery, cruise control, headlight relays, mega-wiring for the EFI and sensors and all that stuff, foglight wiring to PDC, washer tank, air filter box, power brakes, hydraulic clutch master cylinder, front differential hangs from engine mount brackets, EFI fuel rail, all the AC stuff....... and I'm sure I'm forgetting about something. The engine bay is only a fraction the size of my Javelins and the 4.0 isn't a tiny six.

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Posted By: ChillyB
Date Posted: Jul/13/2019 at 7:32am
Running an AC compressor (parasitic load) to cool your air charge is not a way to make power.  It's a reasonable way to lose power, and without making the cabin comfortable.  The compressor will sap more power than the cooler charge could ever provide.  


Posted By: Gelalthedamned
Date Posted: Jul/19/2019 at 10:13am
Originally posted by billd billd wrote:

Use the factory air opening next to the radiator and let the air get to the intake through the very front.....

 
 Billd...do you like Star Wars?


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Calamity - 73 Gremlin X zombie rod (daily driver)


Posted By: Gelalthedamned
Date Posted: Jul/19/2019 at 10:31am
because..guess what 



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Calamity - 73 Gremlin X zombie rod (daily driver)



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