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Header Install
By Dewayne Parrish (a.k.a. Evil) and Richard Cowan (a.k.a. RCowan99SSconv)

This is a step by step documentation of how we installed Mac Headers & Y-Pipe on my buddy Jerry's 99 Trans Am. The purpose of this article is to give those of you who choose to do your own modifications some guidance and hopfully make the job a little easier.

A few notes before we begin...

This modification can be very time consuming..especially since this is your first time, so plan a whole day to complete the install. Get one of your friends to give you a hand. Its much easier to do modifications like this one when you have someone to help you. Some of the bolts are in tight places that are kinda hard to reach.. If you start having trouble with something, don't get frustrated! Sit down, take a break and try again later.. or let your friend give it a shot while you take a break.

Follow safety procedures! When jacking up your car, make sure it is properly supported!

Disclaimer: We are not responsible if you screw something up while trying to perform this modification. This article is just for guidance, and we make no guarantees. Do this mod at your own risk!

Lets get started.

You will need the following tools to complete this install:
1/4 with extension
3/8 with extension
breaker bar

10mm d.w.
5/8 spark plug socket


4 ton jack & jack stands
Flat head screwdriver
8mm x 1.25 tap
Safety glasses
anti-seize compound

1. Disconnect the sensors and remove the lid & MAF. Just remove the whole assembly at once by using a flat head screwdriver to disconnect the clamp that holds it to the throttle body.

2. Disconnect and remove the A.I.R. tubes on both sides of the engine. Use a 10mm socket with an extension. Be sure not to lose the gaskets! BTW, the windshield cowl makes a perfect bolt/tool holder. (see pic below) :)

3. Remove the EGR valve. You will need a 15mm socket for the mount and a 10mm socket for the bolts at the bottom connection and the bolt that holds the EGR to the throttle body. Be careful not to lose the O-Ring gasket and don't let it fall into the intake when removing the EGR from the throttle body.

4. Disconnect the coil packs and plug wires and then remove the coil packs on both sides of the engine. There are 5 coil pack bolts on each side. They're the ones that have a threaded end exposed (not the ones with the "spears" on top) and you can tell which ones are right because they thread into the bosses on the valve covers... you can see those bosses on the pics that show the valve covers.  Note: The furthermost coil pack bolt on the passenger side is a real bitch to get out. When reinstalling the coil packs, you might consider leaving that bolt out permanently. It'll be fine without it.

5. Disconnect and remove the dipstick tube (15mm socket). Gently wiggle it back and forth while pulling upward.

6. Remove the passenger side valve cover.

7. Now go under the car and remove the two bolts holding the Y-pipe to the hanger. (15mm socket).

8. Unclip and remove the 02 sensors.Use a 7/8 open end wrench. Be VERY careful not to drop them or touch the bulb or else they might not work properly when reinstalled.

9. Remove the 3 bolts on each header flange. The bolts might break off, but don't worry because you don't need them anymore. You will need an extension to reach them.

10. Disconnect and remove the driver side catolatic converter from the Y-Pipe.

11. Remove the support bracket located under the Y-Pipe (near the intermediate pipe connection), and then loosen the clamp on the intermediate pipe. You should now be able to remove the Y-Pipe from the car.

12. Now disconnect and remove the stock exhaust manifolds and plugs (now is the perfect time to replace your stock plugs with some NGKs). The bolts are 10mm and there are 6 on each side. The manifolds will drop out from the bottom of the car. Keep the stock gaskets because they will be reused.

13. You may need to clean the  threads on the AIR and EGR fittings on your new headers with a tap--( 8 x 1.25) . 14. Now to drop in the Mac headers. The driver side should drop right in, but you'll probably have to jack up the engine a little to get the passenger side header in place. It will take some work, but it will go. Have your friend get under the car and help you guide them in. Once you get the headers in place, you can use some wire to hold them until you get the bolts in.

15. Now you can bolt the headers to the block. Reuse the stock gaskets and bolts. Coat the threads with anti-seize compound. Torque them from the center out.. 11 ft lbs for the first pass and then make another pass at 18 ft lbs.

16. Now bolt up the Mac Y-Pipe and reinstall everything in reverse order. Get your friend to slide under the car and help you guide the oil dipstick tube into place. Reinstalling everything else is pretty straight forward.

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