Chevy Header And Exhaust Tech - CHP Insider

Dan Lemons Of Lemons Headers Breaks Down Header Design And Exhaust Science

Stephen Kim Aug 1, 2008 0 Comment(s)
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"Heat retention does make horsepower, according to the dyno guys, but I don't know that there is any scavenging benefit," Lemons says. "I do feel there is some benefit to a header that is well-coated on the inside to help control rust and carbon buildup, which could disturb the gas flow. When installing ceramic-coated headers, they should first be wiped down with rubbing alcohol. Use a clean white cloth to apply the alcohol, then a clean dry white cloth to remove the residue. After the headers have been installed, repeat the alcohol cleaning process to any accessible areas. This will remove the fingerprints, grease, excess antiseize, and smudges. Next, start your engine and let it idle for about five minutes, then shut it off and let it completely cool down. Run the engine again for about 10 minutes, then let it cool down. This process will help bake the new finish on, making it tougher, and will greatly reduce the chances of dulling."

Custom Headers
With a plethora of off-the-shelf headers on the market, most hot rodders have the luxury of buying a set that suits their application right out of a catalog. However, uncommon combinations, such as an 18-degree-headed small-block in a third-gen Camaro, will probably require a set of custom headers. According to Lemons, customers can expect to pay roughly $1,200 for a set of mild-steel custom headers. "In our jigs, we have the ability to build a header for any cylinder head as well as different deck heights," he explains. "We can make it in the tube size the customer needs and in a stepped or nonstepped configuration, but the engine needs to stay in the stock location. It takes us about two days to build a header once we start on it, but because we custom-make every header, we always have a lead time. If you need your headers by a certain date, be sure to give your builder plenty of advance notice."

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Tri-Y Headers
Four-into-one headers are the most popular design on the market, but tri-Y (four-into-two-into-one) headers are another alternative. Tri-Ys join two pairs of primary pipes together in a Y-shape ahead of the collector. This essentially shortens up the primaries and merges them into a secondary pipe before reaching the collector. "They tend to scavenge well and can broaden the powerband, but they can be finicky and you may spend a lot of time on the dyno finding the combination that is perfect for your setup," Lemons explains. "Some of the race teams that were using them have gone back to a four-into-one style header because tri-Y headers are too sensitive to minute changes in design."

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Surviving Wheelstands
"We started this business building drag race headers, where there are two high priorities: spark plug room and ground clearance," Lemons says. "It's a constant challenge for us. Most of our new Pro Touring and drag racing designs have the primary tubes actually higher than the bottom of the oil pan. So if your wheelstand got to the headers, it got the oil pan too. We put a lot of effort into improving and redesigning our headers. If we feel we can pick up a little more ground clearance, increase space around the starter and oil pan, or improve access to the spark plugs, then we'll redesign a header. On our big-block headers, we TIG-weld silicon bronze on the outside of the flange to keep the tube from cracking, but keeping them off the ground is the key."


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