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Old 01-08-2019, 06:48 PM
dano73 dano73 is offline
232 I6
 
Join Date: Oct 11, 2007
Location: Long Island New York
Posts: 91
Manifold Air Tube Function

What is the purpose of the manifold air tubes? I usually take them out and plug em, but on closer inspection, am I wasting my time? The tubes are just passively transferring hot air? So I can just break em off at the fitting with no exhaust leak?
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Old 01-08-2019, 07:14 PM
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fsj454 fsj454 is offline
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PLUGS

My manifolds are out of the jeep on the bench . So I removed air tubes and put plugs in today . Next I will paint wit Por -15 exhaust paint silver rattle can . I have used it on exhaust pipes works good . Activates with heat to harden . NO NO AIR TUBES MUST BE PLUGGED OR IT WILL LEAK
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Old 01-08-2019, 07:33 PM
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nograin nograin is offline
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Location: Philadelphia, Pa., USA
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Quote:
Originally Posted by dano73
What is the purpose of the manifold air tubes? I usually take them out and plug em, but on closer inspection, am I wasting my time? The tubes are just passively transferring hot air? So I can just break em off at the fitting with no exhaust leak?
Intake - needed for choke.

Exhaust - those are air injection tubes directly into the exhaust. The oxygen helps reduce left over HC and also increase the exhaust temperature going into the catalytic converter. Once the engine is warm, '85 and up systems inject air directly into the cat. A check valve should be located on each injection manifold/tube.
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Old 01-08-2019, 10:20 PM
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ZackN920 ZackN920 is offline
350 Buick
 
Join Date: Nov 18, 2015
Location: Stephenson County, IL
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If you leave them open, they will most likely blow some exhaust even with the check valves. Mine do. I'm thinking of taking the check valves off and putting on some kind of block off in their place. I'm afraid to touch the individual bolts that go in to the manifolds. Last thing I need is for one to break.
Oh, and if you just break them off at the base they will most definitely blow exhaust out, so don't do that. That'd be bad-mmmkay...

I still don't understand why AMC had to install them like they did. Could of made it simpler like my Dodge 3.9. Just one hole for the air tube to go to in the rear of each manifold. and NO hollow bolt that goes through that hole, an individual hole for bolt to hold down the tube assembly.
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Old 01-09-2019, 09:46 AM
dano73 dano73 is offline
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Join Date: Oct 11, 2007
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Yeah I know all about breking them. If you look into the exhaust manifold, off the engine, the plugs dont have holes in them. The air tube itself goes into a spacer under the hex head of the plug. What Im saying is how does air get injected into the exhaust since there seems to be no hole in the in the plug going into the manifold, that would allow air in.
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Old 01-10-2019, 08:51 AM
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nograin nograin is offline
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Air injection manifold.


Bolts in manifold.
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'85 Grand Wagoneer
360 727auto, NP229
body by beer (PO)
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no "wood" outside
My other car is a fish
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  #7  
Old 01-11-2019, 10:46 AM
dano73 dano73 is offline
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I dont need them, no emissions here. How does air get injected past this solid bolt? Trying to post a pic but cant. The bottom of that bolt is solid right? So when its threaded in the manifold that hole in your pic, lines up with the spacer on the air tube assembly right? And where does the injected air go from there? Since the bolt is solid, right?
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Old 01-11-2019, 10:54 AM
wiley-moeracing wiley-moeracing is offline
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the bolt is hollow inside so the air goes through it, they are not regular bolts.
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  #9  
Old 01-11-2019, 02:02 PM
dano73 dano73 is offline
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The air injection plugs that go in my manifold are indeed hollow, but the bottom of the threaded plug is solid, I dont see how any air is getting pumped into the exhaust.
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Old 01-11-2019, 03:54 PM
zyzx zyzx is offline
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The spacer that is connected to the air tubes (the part that the bolt goes through first) has a diameter that is slightly larger than the bolt. That part of the bolt is not threaded and also has side holes connected to the hollow center of the bolt. This creates enough space to route the air from the air tube spacer through the bolts side holes then down the main hollow bolt shaft. This is why it's a good idea to use crush washers on either side of the spacer to create an air tight seal.
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