Installing a After Market Header 4th/5th Gen Preludes

II. After Market Header.

1. Install the After market header. First, install all the new gaskets, making sure the orientation of the manifold gasket is correct. Apply anti-seize compound to manifold studs and nine new self-lock nuts.

Install the stud bolts on the bottom of the manifold and carefully mount the Header. Finally, torque the self-lock nuts. It is probably best to tighten each nut a little at a time. The proper torque spec is shown in the service manual and Mugen instructions.

2. Check catalytic converter heat shield clearance. On some cars, the A pipe may not bolt into the catalytic converter without modification. To start the test fitting, it is a recommended that you loosen some of the bolts to allow the splash shield to drop, so you have more room. Install the oxygen sensor, if you haven't done so already. Remember to use anti-seize comound on the sensor's threads and on all other exhaust manifold related threads.

A. Test fit the A pipe. Check to see if the A pipe can mount on the catalytic converer. If it clears, you may procede with installation, if not, please follow the two steps below.

i. Verify that twisting the A pipe won't allow it to clear the heat shield.

ii. Loosen the catalytic converter heat shield and mount the A pipe. If the heat shield can be tightened again without touching the flange, continue with installation..

B. If necessay, cut the catalytic converter heat shield. Remove the heat shield completely, taking note of how the second oxygen sensor wires are routed. Bolt the heat shield together with the original bolts. Then, mark off the area you want to cut. The areas to be cut will in front of the front bolts, so there is will be no difficulty when reinstalling. Go back to step A to verify that it fits.

3. Install the A pipe. It is probably easier to hang the A pipe before mounting it to all the bolts. Plug in oxygen sensor, torque all bolts and nuts to spec and reinstall the splash guard.

4. Install heat resistant hose and sheet.

5. Wipe down the exhaust manifold. The exhaust manifold will change color after the first heat cycle and any grease left on the manifold might show up as a discoloration.

Congratulations! U now have a header!