Over the past several months Stainless Works and Kooks have released stepped headers for the 5th generation Camaro SS and are claiming additional gains over their standard straight tubed headers. This has lead to a surge in emails, phone calls, and posts on the forums from people asking “What are stepped headers?” and “How do stepped headers work?”.
Stepped header design was first developed, like most things of this sort, for racing over 40 years ago. They feature an initial primary diameter that at a certain point increases to a larger diameter. For example, a stepped header for a 5th generation SS might start with a 1 7/8 diameter that steps up to a 2 inch. When the exhaust valve opens a pressure shock wave fires down the primary tube at approximately 1500 feet per second until it encounters the “step”. The shock wave is then reflected back up the primary tube towards the exhaust valve. When the steps are in the proper location for the application the reflected negative pressure wave (approximately a 3-5 psi vacuum) reaches the exhaust valve as it begins it’s next opening cycle and assists scavenging.
The key to seeing gains from this design is that the steps must be placed in the proper location for the specific engine the headers are being bolted to. As was mentioned at the beginning of this post, several brand name header manufacturers now have “off the shelf” stepped headers available but that does not mean they will necessarily be beneficial to your car. On a relatively lightly modified car these headers will extract additional power over standard long tube headers but modifications beyond basic bolt-ons can throw off the timing of the shock wave and spoil any potential gains. Camaro SS owners with heavily modified engines that are looking to squeeze out every last raging pony will need a custom built set.