Choosing headers can be a daunting task. With all the different manufacturers, short tube versus long tube, and then there are all the different diameters to consider! Geez. In this post I will try to arm you with as much information as I can to help you decide on the best option for you and your ride.
Short Tube (ST) versus Long Tube (LT)
The general rule when it comes to primary length is that longer primaries will create more low end power and shorter primaries will create more top end power. However, with the larger displacement engines powering the new generation of modern muscle cars (particularly the Camaro and Challenger) it seems that short tube headers are providing minimal performance gains. Because the cost/benefit ratio is so low with the short tube headers I recommend sticking to the long tube headers and will focus on those for the remainder of this post.
Which Manufacturer Should I Go With?
The good news here is that this is hard to get wrong. Ask around on the forums and you will hear some of the same brand names over and over again, I prefer Stainless Works. From a performance stand point all of them are pretty close, no one has a secret that makes one brand produce substantially better results than any of the others. It’s mostly a question of quality and again most of them are pretty close in this area as well, but there are a couple of things to pay close attention to.
Pay attention to what they are made of. Stainless steel (particularly 304) is what you will want to look for. 304 stainless steel will not rust or discolor from exposure to the atmosphere like the cheaper 400 series stainless steel. Unlike aluminized steel, it will not rust from the inside out due to the corrosive fluids produced during combustion. 304 can discolor slightly from getting extremely hot or if you spill engine oil on them but another attribute is that it isn’t permanent.
Pay attention to how they are made. CNC mandrel bending is the best manufacturing method for producing exhaust systems and headers that flow and fit well. When this process is used in conjunction with the 304 stainless steel it allows for the use of a thinner wall tubing that will weigh less than other headers. Those weight savings will be lost, however, if you opt for the ceramic coating some manufacturer promote. With stainless steel the coating isn’t needed for corrosion resistance purposes (ceramic coating is often pushed because the manufacture is using inferior metal) and I have never seen the claimed reductions in under hood temperature demonstrated in hard numbers.
What Primary Diameter Should I Go With?
This is the area that seems to cause the most confusion but it is fairly straight forward. Header manufacturers usually offer two or three options when is comes to primary diameters for a specific vehicle. For example, for the new 5th generation Camaro SS most manufacturers are offering 1 3/4 inch, 1 7/8 inch, and 2 inch primaries. Here are the results of some recent back-to-back testing on an otherwise stock SS:
Stock: 372 RWHP 376 RWTQ
1 3/4 headers with high flow cats: 401 RWHP 404 RWTQ
1 7/8 headers with high flow cats: 408 RWHP 409 RWTQ
2 headers with high flow cats: 413 RWHP 410 RWTQ
As you can see, simply switching from the restrictive stock manifolds to 1 3/4 long tube headers is worth approximately 30 RWHP and 30 RWTQ on a bone stock Camaro SS. The larger the primary diameter gets the more air the headers will flow and the further up the RPM range the power band is moved. The impact of the larger primary diameters is magnified the more powerful the engine is, especially when you introduce forced induction. This means that generally the more power you make or the more race oriented your application is the bigger primary diameter you need, the closer to stock or the more street oriented the smaller primary diameter you need.
In the specific example of the 2010+ Camaro SS, we have found that the 1 7/8 long tube headers are the best all around header for the typical bolt on modified car that is driven regularly and occasionally taken to the track. They offer a tremendous improvement over stock with room to grow as owners modify their car further. The 2 inch headers offer very similar numbers to the 1 7/8 headers up to 5000 RPM where the 2 inch headers pull ahead. They are ideal for those running forced induction or for race applications.
Selecting headers does require some technical knowledge, but it isn’t the voodoo some make it out to be. Hopefully, the information above will put you on the right track but any competent retailer or performance shop specializing in your vehicle should be able to provide further advice.