DC Sports, well known for its 4-2-1 design headers, recently developed a 4-1 header to add to its existing line-up. These headers were designed after the company’s World Challenge Integra Type R race cars’ headers, and are said to extract more horsepower throughout the powerband than any other 4-1 header. The header features large-diameter equal-length header tubes mated to an offset merge collector that provides better ground clearance, meaning you won’t be scraping your header anytime soon. This header is said to have been dyno-proven to provide excellent top-end torque and power, as well as being CARB exempt and available in both ceramic- coated mild steel and a polished stainless steel. Follow along as Frank from DC Sports installs a stainless steel 4-1 header onto a ’99 Civic Si.

  • P89010 Image Large
    The DC Sports four-into-one stainless steel header features large-diameter equal-length header tubes mated to an offset merge collector. Available in both ceramic-coated mild steel and polished stainless steel, these headers are CARB-exempt and are applicable to many Honda/Acura engines.
    P89010 Image Large
    The DC Sports four-into-one stainless steel header features large-diameter equal-length he
  • 1999 Honda Civic Si Under Carriage View Downpipe
    1.
    First, raise the car and support it on jackstands. Remove the splashguard on the lower portion of the vehicle, located directly underneath the engine bay. Using a 12mm socket wrench, unbolt the two nuts on the factory header downpipe that connect to the lower exhaust manifold support bracket.
    1999 Honda Civic Si Under Carriage View Downpipe
    1. First, raise the car and support it on jackstands. Remove the splashguard on the lowe
  • 1999 Honda Civic Si Under Carriage View Upper Exhaust Manifold
    2. Unbolt the header downpipe from the catalytic converter by unscrewing the 12mm nut and removing the 14mm bolt for the two spring bolts at the collector flange. You will then unbolt three bolts on the header downpipe from the upper exhaust manifold by using a 14mm socket wrench.
    1999 Honda Civic Si Under Carriage View Upper Exhaust Manifold
    2. Unbolt the header downpipe from the catalytic converter by unscrewing the 12mm nut a
  • 1999 Honda Civic Si Under Carriage View Header Downpipe
    3.
    Remove the header downpipe from the upper exhaust manifold. Disconnect the oxygen sensor. You will be repositioning the oxygen sensor onto the DC Sports header, so don’t put this part away just yet. Are your arms tired yet?
    1999 Honda Civic Si Under Carriage View Header Downpipe
    3. Remove the header downpipe from the upper exhaust manifold. Disconnect the oxygen sen
  • 1999 Honda Civic Si Under Carriage View Lower Exhaust Manifold
    4.
    Use the 14mm socket wrench to disconnect the lower exhaust manifold support bracket. Remove the oil dipstick; you will need to take this out in order to unbolt the exhaust manifold heat shield.
    1999 Honda Civic Si Under Carriage View Lower Exhaust Manifold
    4. Use the 14mm socket wrench to disconnect the lower exhaust manifold support bracket.
  • 1999 Honda Civic Si Engine Bay View Exhaust Manifold Heatshield
    5.
    Remove the four 12mm heads that bolt the exhaust manifold heat shield to the upper exhaust manifold. It will be a tight squeeze, so be sure to use a flex-joint adapter on your socket wrench. Remove the heat shield and store it with your stock header; you will no longer be able to use this heat shield.
    1999 Honda Civic Si Engine Bay View Exhaust Manifold Heatshield
    5. Remove the four 12mm heads that bolt the exhaust manifold heat shield to the upper ex
  • 1999 Honda Civic Si Engine Bay View Exhaust Manifold
    6.
    Use the 12mm socket wrench to unbolt the seven bolts and two nuts that keep the upper exhaust manifold attached to the cylinder head. Again, this will require the usage of a flex-joint adapter on your socket wrench in order to fit around the header tubing.
    1999 Honda Civic Si Engine Bay View Exhaust Manifold
    6. Use the 12mm socket wrench to unbolt the seven bolts and two nuts that keep the upper
  • 1999 Honda Civic Si Header Component View
    7.
    Remove the upper exhaust manifold section and place it with the rest of the factory header components. You can reuse the manifold gasket if you choose, but it wouldn’t hurt to use a new gasket or an aftermarket metal gasket. This will ensure a tight seal between the cylinder head and the header, eliminating any exhaust leaks.
    1999 Honda Civic Si Header Component View
    7. Remove the upper exhaust manifold section and place it with the rest of the factory h
  • P89170 Image Large
    8.
    Remove the oxygen sensor from your factory header downpipe and place it onto the DC Sports header. Use anti-seize when transferring the oxygen sensor to prevent any unwanted rust from building up.
    P89170 Image Large
    8. Remove the oxygen sensor from your factory header downpipe and place it onto the DC S
  • P89171 Image Large
  • 1999 Honda Civic Si Under Carriage View DC Header
    9.
    Attach the donut flange to the header collector that connects to the catalytic converter. Working from the bottom up, wiggle the header upward, driver-side up first. Line up the upper portion of the header to the cylinder head studs, then place the upper header to the cylinder head and hand-tighten the nuts to keep the header in place. Use anti-seize on all the bolts and nuts that are included with the DC Sports header.
    1999 Honda Civic Si Under Carriage View DC Header
    9. Attach the donut flange to the header collector that connects to the catalytic conver
  • 1999 Honda Civic Si Under Carriage View DC Header Catalytic Converter
    10.
    Torque down all the nuts and bolts to factory specs while using an inside-out tightening pattern. Tighten all bracket nuts, as well. You can loosen the top hanger bolts to make the bottom portion easier to bolt down.
    1999 Honda Civic Si Under Carriage View DC Header Catalytic Converter
    10. Torque down all the nuts and bolts to factory specs while using an inside-out tighte
  • 1999 Honda Civic Si Under Carriage View DC Header Finished
    11.
    Use an all-purpose cleaner to polish off the header after the installation. This will remove any stains and fingerprints encountered during the install, and will keep your new DC Sports stainless steel header looking brand new.
    1999 Honda Civic Si Under Carriage View DC Header Finished
    11. Use an all-purpose cleaner to polish off the header after the installation. This wil
SOURCE
DC Sports
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