I recently installed headers on my Z. They were not DC, but were made by alpha works. However, the basic procedure should be the same.
You need to just accept the fact that this is going to take you some time to do. Obviously where you do it may increase or decrease the time, but wherevver you decide to do it, just keep in mind you will need to get it off the ground. You can not install these from the top.
Make sure you have new gaskets that go between the header and the head and also the header and the cats/down pipes. You can not get these at your local auto parts store and more than likely they are special order through Nissan. They should be able to get them in about 2 days.
You have no choice....drain the radiator! You will be removing a lot of the plumbing for your engine. So you will need replacement coolant when the job is done.
OK...now that all the basics are out of the way you can get started.
Disconnect the negative terminal of your battery.
Remove the engine cover
Remove the strut bar
Remove both splash guards under the car.
Remove the exhaust support bracket between the cats..(4 bolts)
disconnect the cats from the stock manifolds. With a little work (and maybe a hammer) you should be able to seperate the cats from the manifolds. There are 3 nuts on each...notice that one bolt is welded to the stock manifold. If the DC headers do not have a bolt welded to them you will need to buy 2 bolts and 2 nuts to finish assembly.
You now are clear from the bottom of the car. Time to move back to the top.
You will need to disconnect both oxygen sensors for the stock manifolds. there is one on each side of the intake manifold. There are also a lot of wires/hoses/piping in the way for you to be able to get a socket down the side of the engine. Remove as much as you can...It will make it easier and faster in the end.
REMEMBER WHAT YOU REMOVED. IT ALL HAS TO GO BACK
Remove the heat shields from the stock manifolds. 3 or 4 bolts
Once you have access to all 6 bolts on each manifold remove them and take the manifold out through the bottom of the car. Be careful not to break the o2 sensor canles while removing the stock manifolds. The O2 sensors need to be removed from the manifolds and put into the new DC headers. Nissan calls for a special tool to do this...I just used a wrench.
Now that you have the old manifolds out the new ones can go in. With my alpha werks headers I had to disconnect the steering column control arm and move it aside in order to get the headers into position.
Place the new gasket into position and install the header. There is a tightening sequence for this and you can find it in the shop manual. Basically the idea is to get an even tightening across the header. So take your time and tighten all bolts a little at a time. I am also sure there is a torque spec for these, but getting a torque wrench in there is not so easy. Make them tight. Leaks are bad!
Install the other side and repeat the tightening proceedure. There should be enough clearance on the passenger side so that nothing additional needs to be removed.
Now your headers are installed...you just need to put everything you took off back on the car. be careful of any gaskets for the cooling system you removed. It is always best to use a new gasket if available.
Make sure all hoses, fuel lines and wires are not touching the new headers. The heat shields are gone and you don't want to burn a fuel line!!!
Be sure to reconnect your O2 sensors.
Estimated install time: 1 person
Good mechanic 8 hrs
Regular Joe 10+
You will need a good set of metric tools with several different extensions, deep well sockets and universals.
Hope this helps...Let me know if you have any questions.
I think you pretty well covered it! I didn't see anything different from what I did when I installed mine. Like B said, planning on being there awhile, it's not difficult but be sure to take your time and do it right.
Oh yeah, when everything is back together and you don't see any loose parts or bolts on the floor you know you did well :clap:
I shopped around a while until I had mine installed. Most people wanted $600+ for the installation. I got lucky and had the guys at 350forums do it for $300 when they were still doing work on Zs. To my knowledge they just sell Z parts now, don't know if they still do installs. Took them 6 hours. After watching them, it was worth it. Too compact in there and I just go as far as changing the oil and doing minor repairs. I did the header install on my 1971 Oldsmobile 442 W30, took me and a friend an hour :goodtimes: . You can almost sit in the engine compartment and it has a 455 in it.
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