981 GT4 Headers Installation Guide

This document contains information regarding the installation of GT4 Headers.

GT4 Headers CoverGT4 Header banner

  • Allow exhaust to cool entirely before starting install.
  • Always ensure that the vehicle is properly supported on jack stands on a stable and level surface.
  • Dundon Motorsport is not responsible for any personal injury or damage(s) caused to a vehicle during the installation of our products.

 

Tools:

  • T 25 TORX SOCKET
  • 10MM SOCKET
  •  E12 REVERSE TORX SOCKET
  • 12MM SOCKET
  • 13MM SOCKET
  • 12MM SWIVEL SOCKET
  • 22MM OPEN END WRENCH (FOR 02 SENSORS)
  • 13MM OPEN END WRECH
  • 15MM SOCKET
  • 3/8 SWIVEL
  • 3/8 EXTENTION 6IN AND 12IN
  • ¼ DRIVE RATCHET
  • 3/8 DRIVE RATCHET

Approximate installation time for this job is 3-4 hours.

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Remove under tray.

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Remove left and right cross braces.

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  • Unplug O2 sensors from forward bulkhead of car.
  • Undo O2 wires from their factory mounting points on engine and let the wires hand down. Take time to look how they are routed.
  • Remove bolt holding headers to mounting bracket. 1 per side 13mm hex head. You will see 2 bolts here; remove the one closest to the front of the car.

GT4 Header 3

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  • Remove 4 nuts at the header to muffler connection 2 per side.
  • Remove 9 E12 bolts (star shaped head) holding stock headers to head.
  • Remove stock headers from car.

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  • Remove exhaust bracket from head. 2 E12 (star shaped) bolts per side. These will not be reused.

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  • Loosen muffler mounting bolts. 2 at the tip, 2 above the tip and 2 at the mounting bracket. 13mm hex 15mm hex and E12 torx.
  • Remove O2 sensors from stock headers.
  • Install O2 sensors into DMS headers before they are put in the car. Grey wire in the tall O2 bung and green in the short O2 bung. 

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  • In the parts kit find the 18 studs in the bag (labeled Runner to Head studs). Thread them into the head until they stop and make them finger tight.
  • Install manifold gasket over studs.
  • Remove (capped off 4th pipe) from headers for easier install. Pipe will be marked DMSR.

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  • Install header over studs and loosely start nuts from bad labeled (Runner to Head Nuts).
  • With hardware from bag labeled (Rear flange hardware) loosely bolt headers to muffler using new
    supplied gaskets.
  • Install springs (2per side) using the supplied orange handled pick to aid in pulling the spring.
  • The springs hook to the tabs welded to headers. Use pre-installed spring as a guide for this.
    Tighten bolts and nuts starting with headers to head, then headers to muffler and then finish with
    muffler mounting bolts that were loosened earlier making sure to realign tips.
  • Tighten hardware to 30nm.
  • Run The O2 wires back along the valve covers and secure them behind the plugs for the forward 2
    coils on each side.
  • To do this, unplug the coils and route the wire behind them and then plug the plug back in to secure
    the wire behind it.
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  • Ensure the O2 plugs are placed back in the stock holding brackets at forward bulkhead and check
    that wires are away from the new exhaust.
  • Install the (capped off 4th pipe) and install the 3 springs to hold it in place, using the supplied orange
    handled pick. It will aid in pulling the spring.
  • Wipe fingerprints off of headers and start the car.
  • Check all connection points for leaks.
  • Reinstall cross braces and under tray.

GT4 Header 10

NOTE:

The headers on the passenger side may not fit perfectly. To amend this, cut into the undercarriage to allow the header to fit properly. Additionally, note that the fourth runner will not get as hot as the other three. Refer to the photos below:

GT4 Header 13-1

GT4 Header 12-1