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Port Dividers

Do I really need a port divider? Will I get better performance or an increase in mileage? Will my exhaust system sound better with the port divider? Will a port divider help to prevent blown header gaskets? These are questions that have been asked and discussed many times on the fordsix forum. They are also questions I get via e-mail, almost on a weekly basis. As such, I decided to share my thoughts and let you make up your own mind.


Without Port Divider
With Port Divider

First, the port divider is a small "T" shaped piece of cast iron, which was designed to separate the siamese ports on the small six cylinder head. According to the manufacturer's website, installation of the port divider helps to create equal exhaust flow in the 3rd and 4th ports, which in-turn creates equal amounts of power from each cylinder at all RPM's, thus resulting in an increase in horsepower up to 10%.

However, we have never seen any documented proof, hard data, or dyno results, which support the manufacturer's claims. Nor has there been any independent testing, that we are aware of. As such, we will not dispute their claims. We will only state what we know to be true, and what we have heard from forum members.

First, in order for each cylinder to create an equal amount of power, each cylinder must receive an equal amount of air/fuel mixture. Given the design of the log intake manifold, with unequal runner lengths, this is impossible. The center two cylinders receive a greater charge than do the outer two cylinders, and as such the center two cylinders have a tenancy to run rich, while the outer two cylinders run lean.

Ford intentionally designed the cylinder head with Siamese ports, therefore one must assume that they had good reason for doing so. It has been theorized that Siamese ports may provide greater savaging of the exhaust gases, as well as a portion of the intake charge, which may have been done to offset the poor air/fuel distribution of the log manifold. Additional savaging might also assist in lowering cylinder head temperatures? If these theories are true, then a port divider may actually have negative results. No one really knows for sure.....

The manufacturer recommends tack welding the port divider in place, however many forum members used JB Weld in the past. JB Weld was easier, quicker, and cheaper, as the cylinder head didn't need to be removed. As a result, many of the port dividers broke loose, which resulted in a loud and annoying rattle. Not wanting to pull the cylinder head off a freshly rebuilt motor, most simply removed the port divider to put an end to the rattling.

Most members had no idea if the port divider added power, simply because they did more than just add the port divider when they were building their motors. But when they removed the port divider, it gave them an opportunity to see if it really made a difference. According to numerous post in the forum, none of our members observed any difference what-so-ever, in the performance or mileage. Therefore, if performance was increased with the addition of the port divider, it was so minuet that it simply wasn't detectable when removed.

The only difference reported was a slight change in the exhaust note. Some said the exhaust note sounded better with the port divider, while others said it was better without. Therefore one would assume that the exhaust note is much more dependant on the type of exhaust system (single or dual), the use of headers, type of mufflers, compression ratio, cam profile, and so on.

The final question, does it help to prevent blown header gaskets, is a tough one to answer. While blown header gaskets are common on the small six, and have been reported with and without a port divider, there are literally thousands of engines that have never had suffered from a blown gasket. Personally, I think it comes down to following proper installation procedures, and the use a quality header gasket. However, that being said, I would say a port divider might offer a slight advantage, especially if the header is installed improperly.

NOTE: For more information, see our tech article on Header Installation Procedures.

Considering most of the above information is based on hearsay, and not from our own personal experience, we plan to dyno test a port divider sometime in the near future. Our goal is to provide our customers with the best possible advise for building a performance six, even when the product is something we don't make, or sell. We'll let you know how it works out.

NOTE: Manufacturers recommendation for installation. The port divider is to be hand filed until it fits snugly, then placed in the siamese exhaust port (cylinders 3 & 4) and tack welded in 3 spots with N-99 welding rod. DO NOT use brazing or JB Weld.

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