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
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.
procedures! When jacking up your car,
make sure it is properly supported!
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!
will need the following tools to complete this
1/4 with extension
3/8 with extension
5/8 spark plug socket
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.
4 ton jack & jack stands
Flat head screwdriver
8mm x 1.25 tap
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) :)
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
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.
Disconnect and remove the dipstick tube (15mm
socket). Gently wiggle it back and forth while
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).
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
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.
Disconnect and remove the driver side catolatic
converter from the Y-Pipe.
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
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.
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.
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.
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.