Dual Quad Intake Conversion To Dual 2-BBL Throttle Bodies

[98Dak408]

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.

[B Bomb]

Mounting the throttle body is the least of your worries, ie. locating injectors, matching up to Magnum heads, sensors. Save the vintage manifold for a '66 Barracuda project and port your kegger, and throttle body; you will have better flow than the oldie with MUCH less hassle. You could sell the dual quad for enough to finance a reall nice aftermarket throttle body if you so desire.

[b2™]

Well for people who want to replicate this and haven't bought their heads yet. EQ Heads has some 2.02 Magnum Heads that are drilled for the LA intakes. But the problem still lies with injector placement etc.

[98Dak408]

Mounting the throttle body is the least of your worries, ie. locating injectors, matching up to Magnum heads, sensors. Save the vintage manifold for a '66 Barracuda project and port your kegger, and throttle body; you will have better flow than the oldie with MUCH less hassle. You could sell the dual quad for enough to finance a reall nice aftermarket throttle body if you so desire.

Where's your spirit of hotrod adventure?

F&B pulled it off with the old Mopar six pack manifold. It may not work well for me but...nothing ventured...nothing gained.

[98Dak408]

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.

[96BlkDak]

how much power are you hoping to make???

[Grapejuice1998]

Originally Posted by 98Dak408

Are you still going to neck them down to accept 2x2bbl t/b's? If so, why not go with 2x4's?

It will also be interesting to see how you address the injectors and fuel rail.

[98Dak408]

how much power are you hoping to make???

I don't know. This is an experiment.

[98Dak408]

Are you still going to neck them down to accept 2x2bbl t/b's? If so, why not go with 2x4's?

It will also be interesting to see how you address the injectors and fuel rail.

I may fabricate a short 1-2" tall plenum and machine that for the 2x2-bbl TBs to attach to. I'm trying to do this on the cheap and don't want to pay for 2x4-bbl TBs. Perhaps I can modify the plenum that came with the manifold also. Ross Racing has injector bungs that I may purchase and weld into the intake runners. Making and mounting the fuel rails...figuring out the linkage...welding in vertical bolt hole bosses...and tuning will be interesting.

[96BlkDak]

how about machining the 4bbl holes in the first intake into one big ass hole and using 4-2bbl M1 adapters? its a standard 4150 patter at the bottom and a mopar 2bbl pattern on the top.

[98Dak408]

how about machining the 4bbl holes in the first intake into one big ass hole and using 4-2bbl M1 adapters? its a standard 4150 patter at the bottom and a mopar 2bbl pattern on the top.

I've considered that. With the first intake, I would need the 1" spacer and 2-4bbl M1 adapter in order for the TB linkage to clear the fuel rail. That would work.

[96BlkDak]

Originally Posted by 98Dak408

I've considered that. With the first intake, I would need the 1" spacer and 2-4bbl M1 adapter in order for the TB linkage to clear the fuel rail. That would work.

clearing the fuel rail, didnt think of that. I was trying to think of a simple way.

[98Dak408]

clearing the fuel rail, didnt think of that. I was trying to think of a simple way.

Simple is good.

[9t9-5.2]

What about fabricating a intake from scratch?

[98Dak408]

What about fabricating a intake from scratch?

I've considered that but modifying an existing manifold "should" be easier and cheaper. I haven't ruled that out though.