Mac 1 5/8 Header & Y-Pipe Installation Instructions
By Jordon Musser and Brian C. Davis

First and foremost if your planning a Plug wire change go ahead and prepare to do that at the same time. I used Taylor wires, which seem to be of very good quality, except for I was missing one plug wire.

Required Items:
Before the install, get your self some jack stands, new gaskets as a lot of people don't like the paper gaskets that come with the headers. I could not get a hold of Fel-Pros, so I went with a Napa Brand Stock metal replacment manifold gasket and have had no problems. Next get some Antiseize compound, Liquid wrench or WD40, High Temp Silicone Gasket Compound. An assortment of Metric and Standard wrenches and Sockets. One of those Angled pivoting type adapters too. Plugs will have to be removed so might want to consider replacing them and this would be a good opportunity to replace your O2 sensors. If you decide to change the O2 sensors, I recommend getting a O2 sensor socket, as the O2 sensors "hex" is very soft, and easily stripped with open ended wrenches.

Preparation:
The hardest side is the passenger side so pick which side you want to tackle first. I'll describe the passenger side first as I wanted to get the hard part out of the way. Soak down all your manifold bolts that you can possibly get too the night before. An entire night before is not required but it helps. Don't forget to soak the stock Y-pipe to Manifold flange there are 3 on each side. If you still have your cat bolted soak them down too. On the top of the manifold there are compression fittings that are part of the emissions Air inlet tubes. Soak em down.

Installation:

1. Remove the serpentine belt.

2. Jack the car up and get it as high and secure as possible. Remove the Altenator and the black support brackets.You'll notice the back bracket is secured to the 1st Manifold bolt. It's piggy backed on that stud. It has to be removed to get a wrench on that 1st Manifold bolt.

3. Climb under the car and remove the Y-pipe and cat as one piece. Start with the Cat bolts and then get the y-pipe to manifold bolts off and drop this restrictive bitch down and out of the way. Don't forget to disconnect the O2 sensor on the drivers side. It has quick disconnect harness connector.

4. Remove the starter. Disconnect the wires to the starter. Should only need to pull 2 wires and it should come down and out. 2 bolts. You will notice from the oil, that I have the famous LT1 intake oil leak.

5. Remove the Oil Dip stick. With the starter out of the way you should see one bolt holding it on the block. This is a bitch! Be careful with it that you don't bend it up and break it. Try to wiggle it straight up. I used a pair of vice grips that I clamped on there just enough to get a hold of it but not too tight to collapse it. It takes some elbow grease but you can get it out.
6. You should have some room now to get at a few of the manifold bolts while your down there. Get all that you can get too. Your also going to have to remove your spark plugs so might as well replace them with some good NGK's but that comes last. Go ahead and pull some plugs too.
7. Back on top remove any remaining manifold bolts. The 1st bolt is a pain in the ass. I had to pull that Power steering fluid pump hose off and out of the way to get a wrench down there.

8. Now loosen the AIR fittings in the top of the manifolds. I had trouble getting to the passenger side one, so I removed the AIR valve from the rubber side, then unbolted the AIR fitting once I had the manifold loosened, and could move it so that I could get to the fitting. If needed, because of lack of space, you can use a mallet to smack the wrench to break these loose.

9. The Manifold should be quite loose and ready to drop out of there but there's a little EGR flange on that back that's still attached. I found it much easier to remove this one bolt under the car. With the manifold loose I could pull it back at an angle so that I could get a wrench on that EGR Flange. Spray some WD40 on it and it will eventually come lose. It took me a while to get it to break lose. Don't bother trying to remove the EGR tube from the back of the intake, it's much easier getting it off the manifold itself.   Disconnect the O2 sensor.

10. With the manifold completely free pull it out from under the car. Pat yourself on the back you’ve gotten the hardest part out of the way.
11. Use the same method on the drivers side. You'll notice that your access to the manifold bolts are going to be much easier. I think I was able to get most of them from the top and maybe the last 2 from under the car. The manifold will drop down and come out from under the car too.
12. With both manifolds out you can now clean the exhaust ports up real good. I used a fine piece of sand paper and some WD40 to clean it up.

13. At this point you will want to start running your new spark plug wires. I used the stock wiring locations, but I used tie wraps instead of the factory looms in most locations. I did however use the first few looms on the passenger side, because the wires must be run so close to the altenator and belt.

14. Install the passenger side header from under the car and let it rest up in there. Install your spark plugs while your down there and don't forget to use some antiseize on them too. You can wait to get the header bolted up some before doing the plugs. Your option.
15. With your header on the passenger side resting up in there reattach the EGR Flange to the Mac header. You'll see the little recieving flange on the Mac header. I felt it was easier to reattach this while the header was sorta floating up there. That way I could move it around a bit to get the best angle on reattaching the EGR flange.
16. Back up top and using the new bolts supplied get the headers bolted to the heads but don't forget your gasket has to go in too. I was able to slide the gasket in and lined up a bolt and got a couple started. Make sure you apply some Antiseize compound on all header.
17. Before you install the drivers side header, feel free to yank off that plastic crap around the steering column. You don't need it and all it does is gets in the way. Install the drivers side header but leave off the primary slip tube. Get all the bolts on there finger tight but don't tighten them down yet. Apply some of that High Temp silicone gasket stuff all over the portion of the slip tube that goes into the header so that when you tighten it the sealer will aid in making sure there are no leaks. Once it's in bolt the tube to the head and tighten everything down good as you can.
18. Back under the car tighten the primary slip tube. Looks like a little band clamp down there near the steering column. Get it as tight as you can but don't break anything. Install your plugs on your drivers side now.
19. I know your ready for the y-pipe but you have to put the Dipstick tube back in first and the starter. It would be a bitch to try this with a Y-pipe in the way. Trust me I know. I forgot and had to take the Y-pipe back off. Major PITA. Proceed with the pleasure of getting the dipstick back in. You'll be inventing new 4 letter words but it will go back in. If all else fails, I used a little bit of 600grit sand paper to make the OD of the dip stick tube slightly smaller.. made putting it in much easier. After that reinstall the starter and wire it back up.
20. Y-pipe and cat is pretty simple. Start with putting the new or old O2's back in before you drag everything back under the car. Use some antiseize compund. Take the screw in studs and make sure their screwed all the way into the flanges on the headers. I used a pair of vice grips to screw them up tight. Now hold the Y-pipe up there and bolt it in good and tight. If you want to use some of the high temp Silicone gasket stuff on the lips of the Y-pipe to Header feel free to use a little. Plug your O2's back into the harness. Make sure when you attach them you hear the connector click. I had one on the passenger side that didn't close all the way and kicked and SES up. You may need to tie-wrap the O2 wires away from the header on the passenger side.
21. Bolt your Cat on, Reinstall your altenator. You should have some beveled washers/spacers in your kit. They drop into the air inlet tubes sticking up on the header. One on each side. I droped the bullet shaped side in first (flat side pointing up) then screwed the bullet side of the compression fitting into the inlet tube and then reattached those hoses. Remember the one I described removing with the help of a mallet? Yeah that one. Reattach the plug wires. Make sure NO wires touch the headers, use tie-wraps to keep the wires in place.

22. Get your serpentine belt back on and that should be it. Hope I haven't forgotten anything. Check over all your header bolts and make sure they're as tight as you can get them. Start the car and let it idle. As the headers get hot they'll burn off all the grease and gunk from your hands. Expect them to smoke for a few mins. Get the car off the jack stands and take it for a spin. After a couple days retighten your header bolts. Maybe one or two that will tighten a bit more now that they've gone thru a few heat cycles. Also you'll notice a burnt smell for a couple days. That's the coating on the headers setting in. It will go away but make sure you don't have any plug wires touching. Use plastic tie wraps where neccesary.