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Thread: Dual Quad Intake Conversion To Dual 2-BBL Throttle Bodies

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    Default Dual Quad Intake Conversion To Dual 2-BBL Throttle Bodies

    I think I am going to try to convert an old low rise Chrysler 273 Offenhauser dual quad intake manifold to fit my Magnum and run two 2-bbl throttle bodies on it. I plan to modify two OEM 50mm TBs which should provide an inexpensive way to substantially increase the cfm for the engine without buying a 4-bbl TB or 58mm TB. The manifold may also provide more even flow to each intake port. I have the OEM TB off my 360 and can pick up another one from a junkyard on the cheap. I will weld in injector bungs and convert to the vertical bolt pattern necessary for the Magnum head. I'll have to figure out the cooling hose location from the LA style to the Magnum. I will try to hook the accelerator and cruise control cable to the front TB along with the MAP sensor. I will also try to hook up the TV cable to the back TB along with the IAC motor and TPS sensor. I may try to use the conversion adapters for a 4-bbl to 2-bbl or make some type of attaching plate.

    I am all ears to pros and cons including ideas for this set up.

    I just purchased this used and unmodified intake to play with.


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    Sweet idea...I thought about that old 6 barrel manis in the past, with three TBs, except the TBs need to be cut in length so they all fit, but that dual setup sounds sweet. How much did that manifold go for?

    Thing is, you're going to need to cut the 4-bbl holes in each part for the air to flow correctly.

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    Sweet idea...I thought about that old 6 barrel manis in the past, with three TBs, except the TBs need to be cut in length so they all fit, but that dual setup sounds sweet. How much did that manifold go for?

    Thing is, you're going to need to cut the 4-bbl holes in each part for the air to flow correctly.
    I also considered the six pack set-up but as you mentioned, cutting up the OEM TBs might be tricky if not impossible. You would probably want a progressive linkage on that as well.

    The intake was $200 shipped. I'm picking up a small mill in the next little while and I can cut the centers out with that.

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    Quote Originally Posted by 98Dak408 View Post
    I also considered the six pack set-up but as you mentioned, cutting up the OEM TBs might be tricky if not impossible. You would probably want a progressive linkage on that as well.

    The intake was $200 shipped. I'm picking up a small mill in the next little while and I can cut the centers out with that.

    You guys know that F&B makes a six pack manifold & TBs for our engines, right ?

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    That and F&B already makes a bolt-on 6 pack setup. You can even choose how much the 3 t/b's will flow in total.

    http://www.fbthrottlebodies.com/

    On the 2-4's thing, it just wouldn't be the same without actual 4bbl t/b's. It would looked cobbled together with the 2-4bbl adapter plates.

    That's just my opinion though.
    Alan Short
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    Jinx!
    Alan Short
    D.R.T.C. #15


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    You guys know that F&B makes a six pack manifold & TBs for our engines, right ?
    That and F&B already makes a bolt-on 6 pack setup. You can even choose how much the 3 t/b's will flow in total.
    Yeah. The price isn't within my budget at the moment.

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    On the 2-4's thing, it just wouldn't be the same without actual 4bbl t/b's. It would looked cobbled together with the 2-4bbl adapter plates.

    That's just my opinion though.
    With a welder and mill I'm hoping to do it without looking too backyard. Can't look any worse than the 4-bbl M1 with the adapter. I'm also looking into a possible mounting plate like F&B fabricated for their six pack configuration. I'm not really into the bling anyway. I just want form and function.

    Jinx!
    Last edited by 98Dak408; 10-25-2009 at 10:29 PM.

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    From what I can tell, you're a good fabricator and I'm curious what you can do with it. You seem picky enough for it to not look bad so keep us posted man.

    I think on something like that, I'd try to put th inj bungs an inch or so further up the short runners. May help with more topend hp.
    The Dakota RT is gone... but not forgotten.

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    Yea agreed, found out the price and I said forget it. He has me intrigued with what he plans to do now.

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    I think on something like that, I'd try to put th inj bungs an inch or so further up the short runners. May help with more topend hp.
    Thanks for the input. I'll keep that in mind. Injector placement is definately a concern.

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    Quote Originally Posted by 98Dak408 View Post
    Thanks for the input. I'll keep that in mind. Injector placement is definately a concern.
    Only reason I say is I've read some testing on it helping AND you have the opportunity to put it where you want it, to and extent. The runners are short..
    The Dakota RT is gone... but not forgotten.

    '15 Granite Crystal Metallic SRT 392.

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    Looking at the pic again, due to reversion possibilty, I wouldn't full on port match the runners to the heads. I'd leave at least a 1/16 step smaller going into the runner, again, being so short. Don't want fuel and exhaust gases accumulating in the plenums.
    The Dakota RT is gone... but not forgotten.

    '15 Granite Crystal Metallic SRT 392.

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    Looking at the pic again, due to reversion possibilty, I wouldn't full on port match the runners to the heads. I'd leave at least a 1/16 step smaller going into the runner, again, being so short. Don't want fuel and exhaust gases accumulating in the plenums.
    When I port intakes, I'm a little smaller on the intake port than the head intake port anyway.

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    Quote Originally Posted by 98Dak408 View Post
    When I port intakes, I'm a little smaller on the intake port than the head intake port anyway.
    You got it. I was taught, if there's a mismatch, miss it small. Dont want to see the heads flange. That hurts flow more. Best is a perfect match, but given the case, I'd try that first.
    The Dakota RT is gone... but not forgotten.

    '15 Granite Crystal Metallic SRT 392.

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    You got it. I was taught, if there's a mismatch, miss it small. Dont want to see the heads flange. That hurts flow more. Best is a perfect match, but given the case, I'd try that first.
    Exactly! Otherwise you can turn the desired laminar flow into undesirable turbulent flow which is not a good thing.

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    I have been giving further thought to the low rise Offenhauser intake. A few things concern me: 1) The intake port runners are almost too small for me to port to the size of my ported Edelbrock heads. 2) In order for the throttle body to clear the fuel rails I'd have to use the 1" spacer as well as the 2-BBL to 4-BBL conversion adapter. It may be okay but it seems like a long run and then a somewhat sharp 90-degree angle into the port runners. (But there is a plenum at the bottom and it may be okay.)

    I started thinking about using a modified tunnel ram intake instead. It has a nice flowing straight shot into the head ports. There is plenty of room for the injectors. I can make my own adapter plate to the height necessary for hood clearance and can incorporate a plenum for low speed idle quality and MAP signal.

    There was a Weiand dual quad tunnel ram for a 340-360 on ebay that was painted orange (with peeling paint) that bid up to $280 plus $20 shipping so let it go before going that high. This morning I found the same intake in great shape (unpainted and unmolested) for $140 locally, so I snapped it up.

    Whichever intake I decide to use I'll sell the other one. I'm really leaning toward the tunnel ram though.


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    I see another product on your site in the future...lol

    I still need/want an x-brace set from you. I need to win lotto or something because the money tree died...

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    I see another product on your site in the future...lol
    Hey if it works well and can be made without too much expense I just might. The nice thing is you can get the extra CFM without an expensive throttle body. You could also use a modified OEM 48mm or 50mm TB.

    I still need/want an x-brace set from you. I need to win lotto or something because the money tree died...
    I'm thinking of offerring a limited time deeper discount on the x-braces soon and even a group buy price.
    Last edited by 98Dak408; 11-05-2009 at 12:46 AM.

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    Richard,
    When I layed my la style intake up again the magnum heads I had, there was about an 1/8" of a gap all the way around. The intake fit fine on my LA motor but the heads but not on the Mag motor. Maybe my parts were on the outer side of tollerances but the Mag intakes fit fine. I also tried this with a crosswinds manifold (dual pattern) the Mag bolted up fine and the LA leaked because it would not sit all the way down. You might want to check your manifolds with gaskets in place to see if you see the same thing I did.
    Rob Dunn
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    Quote Originally Posted by 98Dak408 View Post
    Hey if it works well and can be made without too much expense I just might. The nice thing is you can get the extra CFM without an expensive throttle body. You could also use a modified OEM 48mm or 50mm TB.

    I'm thinking of offerring a limited time deeper discount on the x-braces soon and even a group buy price.
    Thanks for considering it! I know I bitch a lot about money but I'm sure you know as well as everyone else knows what it's like to not be able to afford any goodies.

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    Richard,
    When I layed my la style intake up again the magnum heads I had, there was about an 1/8" of a gap all the way around. The intake fit fine on my LA motor but the heads but not on the Mag motor. Maybe my parts were on the outer side of tollerances but the Mag intakes fit fine. I also tried this with a crosswinds manifold (dual pattern) the Mag bolted up fine and the LA leaked because it would not sit all the way down. You might want to check your manifolds with gaskets in place to see if you see the same thing I did.
    I'll do some mock-up for the LA intake. It has been my understanding that the Magnum manifold will fit on an A engine and vise-versa. The difference is the verticle bolt holes for the Magnum and the angled holes for the A engine. Nonetheless, I'll be careful to check that the fit is proper. Thanks for sharing your experenices Rob.

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    Contemplating the set-up a little more.

    This shows the TB on top of the base of the manifold. In this situation it would have to be a direct one-to-one linkage because there is no plenum.



    This pic shows the TBs atop the plenum which I would intend to cut down so it isn’t so high.

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    Quote Originally Posted by 98Dak408 View Post
    Contemplating the set-up a little more.

    This shows the TB on top of the base of the manifold. In this situation it would have to be a direct one-to-one linkage because there is no plenum.



    This pic shows the TBs atop the plenum which I would intend to cut down so it isn’t so high.
    I wouldn't want to take too much. The entry have a good approach to the runners like it sits.
    The Dakota RT is gone... but not forgotten.

    '15 Granite Crystal Metallic SRT 392.

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    I wouldn't want to take too much. The entry have a good approach to the runners like it sits.
    As it sits on the base or the plenum?

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