Dual Quad Intake Conversion To Dual 2-BBL Throttle Bodies - Customdakotas.com Forums

**98Dak408** · 10-25-2009, 01:28 PM

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.

AmberFireDaK · 10-25-2009, 03:45 PM

Easier said than done... but if you pull it off it will be cool

You can weld aluminum I'm assuming? have you ever tried to do injector bungs before?

Didn't those offenhauser manifolds use AFB carbs only? don't know how hard that will make trying to mount a TB, not to mention the pair of 2bbl-4bbl adapters your gonna have to run

deanler · 10-25-2009, 07:08 PM

didn't the LA blocks have a different block angle or something? I remember reading that you couldn't use the cams because of that reason and the oiling.

You should buy somecheap edelbrock intakes and just weld bungs in them so I don't have to spend 3 grand on a M1

**98Dak408** · 10-25-2009, 07:36 PM

Quote:

Easier said than done... but if you pull it off it will be cool

You can weld aluminum I'm assuming? have you ever tried to do injector bungs before?

Didn't those offenhauser manifolds use AFB carbs only? don't know how hard that will make trying to mount a TB, not to mention the pair of 2bbl-4bbl adapters your gonna have to run

Hey, nothing ventured...nothing gained.

Yes the manifold takes AFB carbs. I don't anticipate this is going to be a simple bolt-on scenario. When I get the intake in hand, I'll see what I can come up with. Any ideas are welcome.

**98Dak408** · 10-25-2009, 07:44 PM

Quote:

didn't the LA blocks have a different block angle or something? I remember reading that you couldn't use the cams because of that reason and the oiling.

The cams are different since the LA engines used a mechanical fuel pump and the oil passages for the rockers are though the heads instead of the lifters. The difference in the intake is: no injector bungs, the manifold bolts are at an angle instead of vertical, the cooling hose locations are different, and the carb mounts are for AFB.

**98Dak408** · 11-04-2009, 05:09 PM

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.

madmopar · 11-04-2009, 07:15 PM

that's a great find.

**98Dak408** · 11-22-2009, 07:00 PM

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.

**98Dak408** · 02-17-2010, 09:29 PM

Pulled the M1 2-bbl and installed the tunnel ram to check for fitment issues. Looks like I can make it work. A lot of different mods are necessary though. The thermostat water neck is going to be interesting.

94mark3 · 02-17-2010, 09:46 PM

That looks pretty damn awesome!