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4 barrel intake |
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matty 401
AMC Addicted Joined: Jul/06/2007 Location: Iowa Status: Offline Points: 1727 |
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Posted: Mar/11/2018 at 1:20pm |
why is the carb mounted sideways on the 4 barrel intakes ? the 2 barrel is not so why is the 4 ? just wondering
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72 matador 401 the beast
79 concord 2 door 72 matador 304 grasshopper 68 Rogue 406 93 Cherokee 4.0 5 speed |
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billd
Moderator Group Forum Administrator Joined: Jun/27/2007 Location: Iowa Status: Offline Points: 30894 |
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To flow evenly to the cylinders. The two bbl opens both at the exact same time and there's no difference between the two venturis in the two bbl and it sits centered in the middle of the intake so everything flows evenly all directions.
The four bbl has two pairs and the secondaries are a lot different - to have the primaries face forward would put the closer to 1, 2 and three while the back cylinders would be close to the secondaries giving half the engine exposure to the primaries and the back half exposure to the secondaries making it unbalanced - likely by a lot depending on the carburetor. Trace the flow through each venturi to the cylinders and it's pretty plain why the 4 bbl sits as it does - so the front three cylinders get a primary and a secondary and the rear cylinders get a primary and a secondary. Yeah they mix and mingle SOME in the common center area but not enough because FUEL has MASS and thus inertia........ once moving in a direction it wants to keep moving in that direction.
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tyrodtom
AMC Addicted Joined: Sep/14/2007 Location: Virginia Status: Offline Points: 6213 |
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The early factory 2bbl intakes ( 64-80?) had the venturis mounted different than the 81? or later.
They're the same orientation as the 4 bbls.
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66 American SW, 66 American 2dr, 82 J10, 70 Hornet, Pound, Va.
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matty 401
AMC Addicted Joined: Jul/06/2007 Location: Iowa Status: Offline Points: 1727 |
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72 matador 401 the beast
79 concord 2 door 72 matador 304 grasshopper 68 Rogue 406 93 Cherokee 4.0 5 speed |
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Lyle
AMC Addicted Joined: Jul/17/2014 Location: None Status: Offline Points: 772 |
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Ok, very confused here,
The carburetor I have on my manifold is mounted front primaries and rear secondaries. The left side primary and secondary feed cylinders 1,4,6,7 and the right primary and secondary feeds cylinders 2,3,5,8. There is a notch in the manifold between the primaries for balance. Triple checked this. Primary holes are slightly smaller then the secondaries. This is the X3195532C. I thought the casting number was X3195582C but the last 3 had painted over casting flash on further investigation, so the 3 looked like an 8, I'll update that post tomorrow with pictures and dimensions. |
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billd
Moderator Group Forum Administrator Joined: Jun/27/2007 Location: Iowa Status: Offline Points: 30894 |
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Lyle we are in the 6 cyl area - long long intake manifold and three cylinders ahead of the carb and three behind the carb......
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billd
Moderator Group Forum Administrator Joined: Jun/27/2007 Location: Iowa Status: Offline Points: 30894 |
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That was the case as I recall but again, that's a two bbl with the two venturis being the same unlike a four bbl. But there's a reason the 4bbl intakes for 6s are made as they are. I did put a two bbl intake on my 68 232
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tyrodtom
AMC Addicted Joined: Sep/14/2007 Location: Virginia Status: Offline Points: 6213 |
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I meant to say the early 2bbl intakes had the venturis in the same orientation as the aftermarket 4 bbl intakes.
And that's the way i've installed every 4bbl i've installed on 6 cylinders, 4 so far.
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66 American SW, 66 American 2dr, 82 J10, 70 Hornet, Pound, Va.
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billd
Moderator Group Forum Administrator Joined: Jun/27/2007 Location: Iowa Status: Offline Points: 30894 |
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Yes, so you install the four bbl sideways by his description which is the better way. Bowl to the side, throttle shafts running from front to back and not side to side. Yeah but he's asking why are the 4bbls that way. So I explained the reasoning. The last version of the two bbl had the venturis side-by-side, left and right. The bowl to the front, one venturi on the left away from the engine and the other on the right closer to the engine. So when sitting in the car, one on the left and one on the right. The early intakes had the carb sitting so that one was to the front of the engine and the other to the rear of the engine. On a two bbl it matters almost not at all. He's asking why the 4bbl intake has the carb mounted "sideways" instead of the same orientation as a carb on a V8 You installed the 4bbl "sideways" and not like the carb on a V8 by your own description - like the early two bbl intakes. He's asking why are the four bbl sideways. I explained the reason - so the front cylinders are exposed to a primary and a secondary and the rear cylinders are exposed to a primary and a secondary.
To have a four bbl mounted on a six the same way as it is on a v8 would mean the primaries would be closer to the front three and the secondaries closer to the rear three cylinders. A six is long and the manifold is long - the sideways 4bbl puts the primaries smack in the middle and the secondaries in the middle instead of primaries being closer to the front. That's the answer to his original question. |
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Lyle
AMC Addicted Joined: Jul/17/2014 Location: None Status: Offline Points: 772 |
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Sorry wrong thread.
Only true dual plane for a I6 I know of is the Offenhauser C. Primaries go through the top and secondaries on bottom right to the head. Carburetor mount front to back. All others are 90° as explained above. http://www.supermotors.net/getfile/716717/fullsize/offenhauser-intake.jpg Summit has these for AMC.
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