Creating custom part solutions for a build is a requirement when you’ve decided to go in a unique direction with your car. One of the more common areas that need a one-off touch is the exhaust system of a racecar, especially the headers. Our Project Evil Mustang needed some custom pipes made so we turned to Burns Stainless to get the materials to fabricate a killer exhaust.
After the KBX Performance-built small block Ford engine was tucked away between the fenders of Evil and the Vortech blower was bolted on it was time to start creating the car’s exhaust. Fabricating the headers would require high-quality materials due to the extreme environment the car would be operating in.
Vince Roman from Burns Stainless has been assisting racers all over the world for years in the selection process of materials for headers. When preparing to fabricate exhaust, Vince explains why you need to pay attention to the material you select based on the project.
“In most applications, 304 stainless steel is a worthy material to use. It’s good up to about 1400 degrees Fahrenheit, anything above that and you want to go to 321 stainless steel. I don’t think for this application you will see anything close to or above 1400 degrees, so that’s why we went 304. The exhaust gas temperature depends on build and tune — we don’t see typically see above 1400 degrees.”
Since Evil will be using a supercharger as its power-adder, going with the 304 stainless made the most sense. This material provides enough strength for building the headers we need and has the correct amount of heat tolerance, too. There are other materials available, like Inconel 625 steel that will work with high temperatures that Burns offers, however, that would be overkill for this project.
Selecting the correct material for your custom exhaust is the first step in the fabrication process, after that the next important step is picking the wall thickness of the tubing. A balance needs to be struck when choosing the tubing gauge used between the thickness required for the job, and saving weight in a drag racing application.
For Evil, a stepped header approached was used to make sure the headers would not only be sized correctly but be strong enough to deal with any violent chassis movements.
“Normally, for a drag racing application we recommend 18-gauge wall material. What we did here, since it’s a blower car and there’s the possibility for tire shake, we went with a stepped header. The first step we decided to go with 16-gauge wall thickness just to give the headers additional strength at the port where you’ll see the highest stress because of the temperatures. It’s good to put the strength in that location. It will help it minimize cracking as well. We then went to the 18-gauge tubing for the rest of the header,” Vince explains.
Now that the materials had been selected it was time to begin the process of building the headers. We already had an idea on what the final product needed to look like before anything was ordered, but not everyone has that kind of experience. For those looking to build their first set of headers, Burns Stainless has a library of knowledge on their website that you can check out, along with a very helpful YouTube channel that is packed with information.
According to Vince, having good welding habits is critical in building a set of quality headers. If you don’t use a good technique or the right equipment there will be issues during the fabrication process.
“One of the best things people can do is follow the fundamentals like back purging all the welds when working with stainless steel. If you don’t back purge you run the risk of forming carbide precipitates that reduce the strength of the weld. You want to be sure you’re using good practices with the welds so there’s no undercuts or things like that. A good weld should be as strong as the base material. We only do TIG-style welding here at Burns for anything we make. Most production headers are done via MIG and produce strong welds. If you don’t have a good welder or practice enough, MIG wire will go through the wall and cause exhaust flow issues. You can also have rough welds with MIG that will cause stress risers in thinner materials.”
Having a quality set of headers to expel exhaust gasses from your engine will help it run at peak efficiency and generate maximum horsepower. Special thanks to Vince Roman and Burns Stainless for assisting with creating an outstanding set of pipes for Project Evil. Make sure you stay tuned to Dragzine and follow the project here to see what kinds of times Evil lays down when it hits the track.