Here are some photos of the "Dutra Duals" cast iron dual exhaust manifolds for the Chrysler Slant Six. The "Dutra" manifold is a new iron casting, collecting 3 cylinders into a center outlet. This manifold has thick walls plus improved flow. The original "Dutra Duals" were designed to use the new casting for the front 3 cylinders and a modified factory casting for the rear 3 cylinders. I now offer the set with two new castings, machined to fit the and the rear 3 cylinders. ("Mock-up" View) front.
Here is a closer look at the modified factory manifold I use for the rear section. This keeps the factory intake manifold heat riser valve and the stock automatic choke mounting pocket. You can also reuse your current exhaust pipe but it is better to have two new 2 inch header pipes made and fitted to the new manifold set. (The outlet size of both the manifolds is 2 inch) The capped-off section of the modified factory manifold is welded on using nickel welding rod.
See http://www.slantsix.org/articles/exhaust-man-mods/exhaust-manifold-mods.htm for detailed "how-to" info. on making your own rear manifold section. The major issue I have in making these modified rear units is finding good factory exhaust manifold to use as a "core". I request that people wanting a manifold set send me a factory exhaust manifold to avoid a "core charge"
This group of photos shows the routing for the new front manifold's exhaust header pipe. The stock pipe below is hidden. The "Dutra Duals" can be used with any intake manifold such as the Proline Dual Weber or Hyper-Pak but there are special needs for each intake which should to be addressed.
It is interesting to know that this dual manifold set-up idea started as a result of "hand fabricated" units. After doing a few sets this way, ( the "hard way") I went ahead and made-up the casting equipment to do the new front section. If you can machine and weld cast iron then you can make a set of "duals" as shown using old factory manifolds.
The latest version of the Dutra casting now has a larger outlet flange and larger mounting tabs. This allows the unit to be machined for use on the front or rear 3 cylinders. The large outlet flange is designed to accept larger exhaust pipe sizes. When using the new Dutra casting on the rear 3 cylinders, starter motor clearance is tight. "Dual Dutra Duals" can be done but click here to see some of the issues involved.
Be sure to check-out the Slant Six Message Board and tech. article section at www.slantsix.org
Doug Dutra (Doctor Dodge) - SL6@ dutra.org - ( this is not an active link to prevent "spamming")