The first thing that you are going to want to do it lay out all the parts that you are going to need and make sure that everything is there. You will need the Headers, Y-pipe, header gaskets, new header bolts, O2 Simulators, 24 inch O2 extensions, and all the appropriate clamps and plugs if your y-pipe has o2 sensor bungs welded in. I prefer to use a seal clamp whenever possible for several reasons. One, they have a lot better ground clearance and as we all know, that is an issue with Lt’s on our cars. Two is they actually will seal better than a traditional exhaust clamp. Finally they don’t crush the pipe like the old clamps, so if you need to take it apart it all comes off easily. I also recommend that you get these in stainless steel for longevity. I also recommend that you use factory GM header gaskets as they are made from 3 metal shims and will crush down to make an excellent seal. As for the tools needed: You’ll need Metric end wrenches, preferable the ratcheting type, metric ratchet and sockets, a floor jack and jack stands or lift, some zip ties, and a whole bucket of patience!!! Depending on your level of experience the install should take any where from 5-10 hours. The Install is as follows….

1. Jack you car up as high as you can get it and safely secure it on jack stands at all four corners.
2. Remove your Strut Tower Brace (If you have one on your car) It’s much easier to remove it then try to work around it.
3. Remove the A.I.R. components from the factory manifolds.
4. Unplug the sensor wire that is on the driver’s side at the very front of the manifold.
5. Remove the plug wires.
6. Now its time to go under the car. First unplug your rear two O2 sensors that are in the y pipe. Then unclamp the y pipe at the rear or where it connects to your cat back system. Next unbolt the hanger that is attached to your transmission or cross member. Then unbolt the front of the y pipe from the cats.
7. Unplug the front two O2 sensors, and then remove both left and right side cats. There are 3 bolts per flange. You may need a universal joint to get these off.
8. Go back to the top of the car. I started by removing the driver side manifold first but you can start on either side. I was able to get all but the very back bolt out from the top fairly easily. For that last bolt it is much easier to get back under the car and remove it. Be careful taking that last bolt out as the manifold may fall if you don’t have a good grip on it. If it falls you may end up hurt or breaking your spark plugs. It should come out very easily.
9. Go to the passenger side. This side has a little less room to work but isn’t too bad. The same goes over here, remove all but the last one or two bolts then remove the last one from the bottom of the car. Again be very careful not to drop the manifold when it comes loose.
10. Now you should have all the old parts off and be ready to begin installation of the new headers. You may need help at this point. On the driver’s side, you’ll want to remove the number 7 cylinder spark plug, or the very last one. Otherwise the header won’t slide in. Once that is out, everything should go in fairly easily. Be careful not to damage your other spark plugs. You may want to remove them all if you are uncomfortable with trying while they are installed.
11. Once the Header is in place, get the driver side gasket out (there is a right and left side gasket, they are marked to make it easy) Have someone slide the gasket in and start threading one bolt in the front and one bolt in the rear.
12. Once you have the gasket in place, loosely install the remaining bolts.
13. Re install the plug or plugs that you removed earlier.
14. Now you can tighten the bolts, start in the center and work out. DO NOT OVER TIGHTEN!! You can either stripe the head out or you may break the head off the header bolt. The bolts should thread in easily by hand until they are a good part of the way into the head. If they don’t stop and try again, you have them cross threaded.
15. On the passenger side you’ll want to remove all the spark plugs. You can get by with leaving the number 2 cylinder in if you wish.
16. Now slide the header into position, again you’ll need some help here. Have someone place the gasket in and start two header bolts.
17. Now repeat steps 13 & 14.
18. With the headers on go back under the car. Depending on your y pipe you may want to partially or completely assemble it prior to taking it under the car. Install the y pipe loosely and check to make sure it has a good seat at all the joints. If it doesn’t it could leak or fall apart while driving.
19. Once the y pipe is on and adjusted you can start clamping or welding it in place. If you use seal clamps just tighten them until you can see where the joint in the pipe is.
20. Remove the O2 sensors from your old cats and install them in the headers. You’ll need the O2 Extension to get them to connect to the factory harness. Make sure all the wire is tied up and out of harms way.
21. Depending on your y pipe you may or may not have O2 sensor bungs welded in. If you do then either install plugs to close them off, or you can use the old 02 sensors for this. If you do this tie the wires up so they don’t drag the ground.
22. Plug in the two O2 Simulators into the rear two O2 sensor plugs and tie them up as well.
23. With everything under the car finished you can re install the plug wires.
24. Plug the sensor wire back into the sensor at the front of the driver’s side header.
25. Re install the A.I.R. components.
26. Re install the Strut Tower Brace if needed, and you should be ready to fire the car up.
27. Start the car and let it warm up to operating temperature. Check for any leaks, SES lights or other problems.
28. If everything checks out ok let the car cool back down and then check all the bolts again to make sure they are tight.

Origionally Posted on Z28.com by Nic (Mr. Bowtie)

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