Mustang Scott Drake 289/302 Tri-Y Headers (1965-1968) Installation Instructions

Tools Required:
  • 9/16-inch Wrench (2)
  • 9/16-inch, 7/16-9inch Sockets
  • Ratchet
  • Extension & Flex Extension
  • 7/16-inch Wrench
  • Ratchet
  • 13/16-inch Spark Plug Socket
  • Gasket Scraper
  • Hammer
  • Hacksaw
  • Anti-seize Lubricant
Install Difficulty:
  • Moderate
  • Moderate Project
1. To start installing your new Mustang Scott Drake C5ZZ-9430-SS Tri-Y Headers, let the engine cool completely before you begin work. Chock the rear wheels.
2. Before you begin: If your car has power steering, you need to install a Mustang slave cylinder lowering bracket.
3. Unbolt the old Mustang Tri-Y headers at the exhaust flange by removing the three flange bolts on each side. This will require two 9/16-inch wrenches and the 9/16-inch socket, extension, flex extension, and ratchet. If you are replacing an exhaust manifold set-up you will have to cut the exhaust pipes with the hacksaw to allow room for your new headers. You will also have to take your car to an exhaust shop to make the connection to your old exhaust.
Mustang Scott Drake Tri-Y Headers Install Image
Mustang Scott Drake Tri-Y Headers Install Image
4. Remove the Mustang spark plug wires from the plugs. Make sure you mark the wires in some way so that you can put them back on the proper plugs later. Remove the spark plugs. Remove the eight bolts that hold each header or exhaust manifold to the head. The old headers should drop out the back bottom with a little wiggling.
5. Clean the heads where the new Mustang exhaust gaskets will come into contact. Be careful to keep debris out of the exhaust ports and spark plug holes.
Mustang Scott Drake Tri-Y Headers Install Image
6. Pull the new Scott Drake header up from the bottom rear and test the fit. My automatic transmission car required me to unbolt the transmission dipstick tube at the back of the head and pull it towards the Mustang bellhousing temporarily. The dipstick tube did not have to be pulled out of the transmission, just tilted out of the way. Some installers report clearance issues with the shock towers, bellhousing, clutch linkage and spark plugs. It is not uncommon for a header installation on any vehicle to require some modification. Header tubes are easily “tweaked” with a hammer to solve most shock tower clearance problems. A little work with an angle grinder on the header flange will solve the common spark plug clearance issue on the #2 spark plug. A bellhousing clearance problem on the left side can be solved by cutting off the unused tab on the bell housing.
Mustang Scott Drake Tri-Y Headers Install Image
Mustang Scott Drake Tri-Y Headers Install Image
7. Once you are satisfied with the fit, slip the gasket between the header and the head. Apply anti-seize lube to the supplied mounting bolts. Align the gasket and hand thread the eight bolts in. Tighten the bolts with the 7/16-inch wrench.
Mustang Scott Drake Tri-Y Headers Install Image
8. Reinstall the spark plugs and wires. Re-attach the transmission dipstick (if it was removed). If the connections line up, simply use the supplied bolts to attach the existing exhaust flanges to the new headers. Or, if things don't fit perfectly, cut the exhaust and use an exhaust pipe expander to allow the new header collectors to slip inside. Bolt them on to the headers and clamp the pipe connection.
9. After the engine has been through a few heat/cool cycles, recheck the tension of the header bolts. It’s common for them to work loose with the expansion and contraction of the metal. The installation of your new Mustang Scott Drake Tri-Y Headers is now complete.