Well, this seems to have been requested a few times, and would've helped me when I did mine this weekend. So, here's my contribution to the group!
If you're fairly mechanically inclined and have some decent tools, you should be able to pull this off pretty easily. It took me about 10 hours to get this complete, and I think it could've been a little faster had I knew a couple tricks to make it easier.
Sorry there are no pictures, but I don't think there needs to be. Let me know if you have questions and I'll try to help. The pictures in the Service Manual were more than enough for me.
This is for a set of "DNA Headers", which I'm assuming is a ripoff from the OBX design. They look very similar, and I picked up the headers, downpipes and test pipes for $300 online. Fitment of the headers was great...no issues at all. I didn't use the downpipes or test pipes. Honestly, I'm not sure why anyone uses the downpipes since they all look like the OEM downpipes.
I also weighed the OEM manifolds and the passenger side was 13.5 lbs, while the driver's side was 14.5 lbs. The headers were 4 and 5 lbs lighter, respectively, and if you subtract the "Exhaust stays" and bolts, it's a total of 10 lbs lighter. This included the header wrap and clamps I put on the headers before installation.
3/8" drive ratchet, various sockets (10, 12, 14, 17 and 19mm). You shouldn't need deepwell sockets for anything as long as you have extensions (wobble extensions almost required for the installation part), pliers to remove hose clamps, jack-stands, and something to drain your coolant into.
OK, so to start, do yourself a favor and look at the 3.8 BK2 service manual and familiarize yourself with the very short section on removing the exhaust manifold. It's 10 steps long, and overall pretty straight forward.
First, jack up the car and put it on jack stands...I had mine high enough to crawl underneath. Then follow the steps from the Service Manual:
1. Disconnect negative battery cable.
2. Drain the engine coolant from the radiator.
3. Remove the plastic engine cover.
4. Remove the air duct and air box.
- I pulled the 4 inch corrugated intake tube along with the airbox.
5. Remove the upper and lower radiator hoses.
- I just disconnected them from the pipes along side the engine and positioned them out of the way. No need to remove them from the radiator.
6. Disconnect the O2 sensors on the exhaust manifold.
- These are easier to get once you remove the inlet and outlet coolant pipes (So maybe do this after step 8).
7. Remove the "exhaust manifold stays" underneath the car.
- These are the 2 bent brackets attached to the manifold. You won't use these again.
8. Remove the engine inlet and outlet coolant lines.
- Each pipe has a 12mm bolt attached to a mounting tab for stability towards the front of the engine, and another 12mm bolt that holds the pipe in place at the back of the engine where the pipe enters the block.
- In addition, the passenger side pipe has two 10mm bolts attaching a wiring bundle bracket to the tube.
- Once all the bolts are out, wiggle the pipe until it pops out of the back of the engine. Make sure you don't lose the O-ring that's on the pipe (mine stayed on the pipe).
9. Disconnect the downpipe (Service Manual calls it the "front muffler").
- There are two 19mm nuts on each end of each pipe. Take all 8 nuts off.
- I pushed (hard) to get the downpipe to clear the studs on the manifold, then did the same to unattach them from the secondary cat studs. While they were still hanging on the rubber isolation blocks, I just swiveled the pipes out of the way. Don't bother taking them off the rubber blocks...just leave them hanging.
10. Remove both Exhaust manifold heat shields.
- Use a 10mm socket for this. They're not torqued on very tight and they spun off easily once they were initially loosened. The only exception was one bolt on the driver's side shield was cross threaded, so I cut the shield with tin snips around the bolt and just pulled it off.
11. Remove the Exhaust manifold from each side.
- Most of the bolts were easy to get to, including the ones hidden underneath and toward the back of the engine. If you can't get to it from up top, crawl underneath and get a wrench on it from there. With the downpipes removed, there's plenty of room to maneuver.
The passenger side manifold came out through the top, but the driver's side had to exit the car from underneath. Too many lines and things in the way.
That's it for removal!
Installing the header was the reverse of the above, but here are a few hints to make it easier.
- Drain the coolant and get the inlet / outlet pipes out of the way. I read another thread somewhere on here stating that it's overkill, but trust me, it's MUCH easier with them out of the way. As a matter of fact, I tried with them in place much longer than I should have and wasted a couple hours trying to get my hands around them to remove the manifold bolts. Do yourself a favor and drain the coolant. Spend the $6 and buy a new gallon of antifreeze when you're done.
- Swap the pre O2 sensors to the headers before installing them. Then, take the O2 sensors out of the downpipe and make some 5 foot extension cables to have them mounted behind the secondary cats. I will have this done before I start my car, and I'm hoping I never see a CEL. Oh, and don't forget to install the bung plug in the downpipe since you removed the O2 sensor!
- Make sure you remove the original manifold gasket (4 layered steel) and replace with the header gasket.
- The passenger side header went in pretty easy, but the driver's side manifold required the removal of the steering wheel shaft. It's a 12mm bolt at the bottom of the shaft where it plugs into the rack. Do yourself a favor and center your steering wheel before you remove this! Even better would be to center your steering wheel and then mark the shaft position on the spindle that comes out of the gearbox. I used a black sharpie, which was easy enough to see...plus, it's only disconnected for a few minutes while you get the header past the shaft.
- Torquing the passenger header bolts was easy because they were fairly accessible. The driver's side header design put a pipe one inch in front of the #1
bolts along the top of the header...so I had to use a 14mm box end wrench and guess. Bottom of that header, bolt #2
was the same issue...box end wrench was all I could get in there with. I know when my fingers hurt from pulling on a wrench, and it happens to be right in the high 30's for ft/lbs. So I went with that.
Steering column shaft bolt - 13.2 - 17.8 ft/lbs
Header bolts - 36.2 - 39.8 ft/lbs.
Water pipe bolts - 14.5 - 17.4 ft/lbs.
Downpipe nuts - 28.9 - 43.4 ft/lbs.
Header bolt tightening sequence - I can't post the image for some reason, but it's page 887 of the Service Manual.