THE SHOP

July '16

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JULY 2016 THE SHOP 71 PERFORMANCE rials, but you won't encounter high-enough temperatures to justify its use. The primary reason to run titanium exhaust tubing is to save weight—period. If you want to spend the extra dough to lighten the vehicle, have at it. By the way, while Chevy touts the late-model Corvette as having a titanium exhaust system, that only refers to the rear muffler/tip section, not the entire system. It used titanium in the rear in order to shave off a few pounds. Thermal properties are always a consid- eration for exhaust headers. The heat gen- erated by the combustion process should ideally be captured and retained inside the exhaust system as opposed to being allowed to radiate out from the pipes. Containing the heat inside the pipes leads to increased power. Steel tubing tends to absorb heat, making the tube surface hotter as heat is released. This is detrimental to power and causes exhaust heat to increase under-hood temperatures. High-quality 304 or 321 stainless steel is better at retaining heat, promoting a more efficient combustion control (more power) and reduces under-hood radiated heat. Of course, steel headers may be treated to reduce radiant heat loss by either installing thermal wrap fabric or by the application of ceramic coatings. In short, if you're using steel headers, it's wise to have them coated (or buy them already coated) or to wrap the tubes with specialized heat-wrap. If you're running stainless steel headers, the heat will pass through quicker and the surface tempera- ture of the tubes will be lower. If you want to go even further, stainless headers can be ceramic-coated to achieve an even higher level of thermal management. NEXT Next time, in Part 2 of this article, we'll take a closer look at header coatings, as well as port-matching, scavenging, tube- bending and more. MIKE MAVRIGIAN owns and operates Birchwood Automotive in Creston, Ohio, where he builds custom engines, street rods and performs vehicle res- torations. He has written thou- sands of technical articles, as well as nine books on automotive technology during the past 30 years. Mike can be reached at 330-435-6347 or birchwdag@frontier.com. Visit Birchwood's website at www.birchwood- automotive.com.

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