The questions "Are Sanderson headers direct-fit?" or "Do I need to modify my down pipes to connect to Sanderson headers?" are asked regularly, and the answers are simple.
- NO, Sanderson does not manufacture direct-fit headers, and
- YES, modification of the exhaust system downpipes is required!
Please allow me to explain how this can be confusing for some.
This is often a misunderstanding of terminology. Many of us own newer vehicles that we drive daily. We like the warranty, reliability, power, and fuel efficiency that come with all the creature comforts in a modern vehicle. We may decide to upgrade these newer vehicles. And one of the most common upgrades is to change the exhaust system by adding a cat-back kit with different mufflers or installing headers. All vehicles since 1995 (1996 in the USA) use an OBD (on-board diagnostic) system that integrates with the vehicle's computer-controlled systems. To maintain the integrity of these systems, laws were passed to ensure that the various system components received accurate information, thereby supporting proper engine performance and efficiency. This is a GOOD thing!
On these late-model vehicles (as with vehicles of the past), upgrading the exhaust is usually the most cost-effective step to improve performance, but we do NOT want to go backward by compromising engine efficiency. Ensuring the aftermarket performance components are designed to work on these late-model vehicles is extremely important! This includes maintaining the location of components, such as the catalytic converter, and any sensors within or near the factory exhaust. No one wants to spend hundreds (or thousands) of dollars on an exhaust upgrade that causes the engine to run less than optimally due to what was mentioned above. Additionally, because of the implementation of OBD systems, car manufacturers use more standardized designs for these new vehicles. It is too costly to make mid-year changes that redesign, for example, an exhaust system.
However, on our classic cars, trucks, and street rods, this is not the case. A vehicle manufacturer may stick with the same design for an entire model year (or longer), or make numerous changes throughout a production cycle. What if a vehicle manufactured prior to the 1990s used 'X' sourced exhaust manifolds for assemblies between August and October, but that supplier could not keep up with production (or had other problems), forcing the vehicle manufacturer to change suppliers? Brand 'Y' steps up and becomes the source for this manifold through the rest of the production year?
What if there were manufacturing differences between the two manifolds that slightly changed the collector exit location? If a header manufacturer such as Sanderson wanted to build direct-fit headers (no, Sanderson does not offer any direct-fit headers) for this classic vehicle, two header set variations would be required (just for that ONE vehicle)! Imagine for a moment the number of vehicles built since the 1920s, and how many possible variations there could be. For example, some Ford applications have been known to have three or more component variations in a single year. This is costly and a huge waste of time and resources for any header manufacturer.
Headers manufactured for classic cars or street rods are built for a more universal fit. These products are not subject to OBD restrictions and are designed to provide the best fit for a variety of vehicle applications. Instead of building a specific header for each and every possible configuration, Sanderson will often slightly redesign a popular header to provide a proper fit across an even wider range of vehicle applications.
This affects the installation, where specific downpipes are required for our classic car, truck, or street rod to connect the under-chassis exhaust piping to our new headers. This is one of many primary activities at most muffler shops and should not scare anyone away from adding headers to our classic Mustang, Thunderbird, Camaro, Buick Skylark, Dodge Dart, or any of the numerous other vehicle applications for which the header sets are designed.
In a way, we (as consumers and vehicle enthusiasts) have become accustomed to direct-fit terminology because it is the current standard for newer model vehicles. The osmosis of hearing or seeing "direct fit," "smog legal," or "cat-back" in regular advertisements is understandable, as it can cause confusion about the requirements for our classic vehicles. Just remember, it is not the case. Headers for classic cars will require some changes to our under-chassis exhaust piping during installation.