Third-Generation Acura Integra Exhaust Header Replacement (B18B1)

Work only on a fully cold engine, since the exhaust and cooling components reach high temperatures. Begin at the top of the engine bay and loosen the clamp on the upper coolant hose that runs above the driver-side cooling fan. Freeing this hose creates the clearance you will need later to lift the old header up and out.

The header is covered by a metal heat shield held on by four visible bolts. Take all four out; the lowest one is reached most easily from underneath the car rather than from above. Lift the shield away and set it aside for reinstallation or replacement.

With the shield off, remove the eight bolts that secure the upper flange of the cast header to the cylinder head. Apply penetrating oil first if the hardware is rusted, and work slowly to avoid rounding or snapping a stud. Leave the header in place for now; it is still held by its lower connection.

Take out the two bolts holding the driver-side engine fan and unplug its electrical connector, then lift the fan assembly out of the bay. This is optional but strongly recommended, because the extra room makes maneuvering the old header out and the new one in far less of a struggle.

Jack the front of the car high enough to give you working room beneath the engine, then lower it onto properly rated jack stands before climbing under. Never rely on the jack alone; a car dropping on you is a fatal hazard. Confirm the stands are seated on solid chassis points and the vehicle is stable before continuing.

From underneath, remove the three bolts that join the bottom of the header to the exhaust downpipe. The rear lower fasteners are the tightest to reach, so use an extension and swivel to break them loose. Once these are out, the header is fully detached from both the head and the exhaust.

Return topside briefly to free the upper flange fully, then guide the header downward and out through the underside of the car, which offers the clearest exit path. Take care not to drag it against the oxygen sensor wiring or nearby lines as it comes free.

Unthread the oxygen sensor from the old header before discarding the part, since you will reuse it. Handle the sensor gently and avoid getting cleaner or oil on its tip. Note that the aftermarket header has its own matching bung for the sensor to thread into.

Wipe down the cylinder-head flange, the downpipe flange, and the surrounding area with brake cleaner to strip away old gasket residue, carbon, and grime. Clean, flat sealing faces are essential for a leak-free joint once the new header is bolted up.

Assemble any multi-piece sections of the new header on the bench before installation, and install the oxygen sensor into the bung provided on it. Doing this fitment work outside the cramped engine bay is much easier than reaching in later.

Lift the new header into position and start all of the upper flange bolts by hand, making sure a new gasket is sandwiched between the header and the head if your kit includes one. Leaving every bolt loose at this stage lets the header self-align to both flanges before anything is drawn tight.

From below, bring the three lower flange bolts up to the downpipe and tighten them so the bottom joint is secured with its gasket seated. Getting the lower flange located first keeps the header aligned while you finish the top.

Tighten the upper header bolts to 23 lb-ft, working in a criss-cross pattern that starts at the center and moves outward. This sequence pulls the flange down evenly and prevents warping or an uneven crush on the gasket that would cause an exhaust leak.

Reinstall the driver-side fan and reconnect its plug, refit the heat shield, and re-secure the upper coolant hose you loosened at the start. Lower the car off the stands, then start the engine and listen for any ticking or hissing that would indicate a leak at either flange, re-checking the affected bolts if needed.