Installing a set of performance headers on a 1994 to 1995 Ford Mustang GT is a common modification. Not only do headers free up more power, but they sound terrific and let the V8 engine's exhaust tone rumble. They also look great in the engine bay. Installing a set of headers is generally an all day job for the weekend mechanic. Installing headers on other years of the Mustang 5.0 follows the same basic procedure, though the headers themselves will be a different part. The same applies to V6-powered Mustangs.
Let the engine cool off completely before beginning installation of headers. This can be overnight, but should be at least a few hours before the headers are installed.
Disconnect the negative terminal in the battery. Disconnect the two screw clams holding the induction hose from the throttle body to the airbox on either end. Unhook the vent hose from the induction hose and unscrew the air temperature sender. Remove the screw that holds the air box to the fender well. Remove the hoses that go to the smog pump and catalytic converter. Note the position of the vacuum lines.
Remove the spark plug wires and the spark plugs. Jack up the car and place securely on jack stands at all four corners. Loosen the H-pipe flange nuts that attach to the headers on both sides with a 3/4 inch or larger socket. It does not need to be completely removed. The oxygen sensor needs to be unplugged and removed in order to access one of the nuts. Use a 22mm open-ended wrench. Loosen the two screws that fasten the H-pipe to the connector and pull the H-pipe down. Using a 1-inch wrench, loosen the EGR tube from the EGR valve located at the throttle body.
Use a socket to loosen the 16 header bolts (12 on a Mustang V6) using different length sockets, swivel adaptors and extensions to reach them. Remove the dipstick tube to allow removal of the driver's side header. Pull the headers out of the engine bay. This will take a bit of work to get them out. Remove the stock gaskets from the block and scrape off gasket material that is left on the block.
Screw the header studs into the flanges of the new headers using a pair of channel locks. Position the headers into the engine bay. Line the header up with the bolt holes. This may take several attempts to get right. Insert a new gasket between the header and the engine and then loosely install one bolt on either side to keep the gasket in place. You may need an assistant to hold one end of the header in place while the other end is bolted on. Insert the rest of the bolts with anti-seize compound on the threads. Tighten the bolts with the socket until the header is tight against the block.
Reinstall the dipstick tube along with the driver's side header. Reconnect the H-pipe to the new headers. Align the flange of the H-pipe with the studs on the header and slide the pipe on. Carefully tighten the bolts a little a time, alternating each one so that you don't bend or brake the header collector. Reinstall and reconnect the oxygen sensor.
Reconnect the EGR tube loosely on the header, which may be replaced with one that came with the headers. Screw in the EGR at the throttle body and tighten the top and then the bottom. Reinstall the spark plugs and plug wires. Reconnect all of the air tubes that were disconnected. Reattach the battery cable.
Start the car and check for exhaust leaks by listening near the headers. Check and retighten the header bolts if needed after the headers have heated up.
