Exhaust System – Time for Something New

We recently had the opportunity to do a complete exhaust change-out on a 2009 Nissan 370Z. New headers to tailpipes which included high flow cats, allowed us to see what was really involved in making the changeover. Before tackling the work I spent a bit of time on the net checking out information about it. From what I was reading it seemed as if the entire engine needed to come out of the car to do this job. I think maybe some people might go a little overboard but it was obvious that this was not an easy task.

Save for one header bolt that delayed us, the entire job really only took about 8 hours. A lot of that time is spent just trying to figure out what combination of tools is going to fit on that hidden bolt and getting it loose. You also need to not be too squeamish about seeing your own blood either – unfortunately there just isn’t a lot of room to work in the engine bay and everything from small metal tabs to the cut ends of nylon wire ties are going to leave their mark.

The basic plan of attack was to get the car up and supported all the way around. I jacked up the car and placed it on (4) jack stands, made absolutely sure that the car was stable and then I proceeded to start removing the exhaust system starting with the muffler in the back. I chose to unbolt the exhaust hangers from the chassis rather than wrestle with the rubber donuts under the car. It is much easier to get the hangers and donuts off with the parts out in the open and a little bit of spray lube makes it a quick job. Once I had everything off up to the stock cats, it was time to pull the oxygen sensors. You will need a 22mm open end wrench and a ballpeen hammer to get them out. In every case a single tap from the hammer was all that was needed to loosen each one. The real challenge was the front pair and their connectors which are not located in convenient locations. In both cases I found it easier to snap the connector off of it’s mounting bracket which resulted in giving me several more inches of wire slack to work with and made it possible to get them disconnected.

At this point it was time to attack the exhaust headers and yes, I chose to leave the cats attached to the headers. The headers are held in place with 14mm nuts on a stud arrangement. There are 6 on each side of the engine but before you can really get to those nuts, you need to get the heat shields out of the way. The best advice here is to not try and loosen the 10mm bolts holding the heat shields in place. It’s actually quicker to tighten them until they snap off. The top and bottom shields have 3 bolts each. With the shields out of the way, you can now start on the 14mm nuts. What you will find is that the exhaust ports on the engine face roughly about 15 degrees downward which means that when you put a socket on a nut, gravity gets involved and it wants to slide off. In most cases it is just about everything you can do to get the socket on the nut and holding with a second hand is almost impossible. The other thing that will happen is that the stud will come out with the nut. It’s not a major problem and in fact to get the headers off later, it helps to have all of the studs removed so it works out. Getting these 12 nuts off and then later back on is where you are going to spend the majority of your time on this project. Plan on it. Be patient and take your time, if you have trouble with one nut move to another. It’s better to keep making some progress and come back to the tougher nut(s). What I have learned on this is that before I tackle the next one I will make up a 1/4 inch thick piece of metal about 30 inches in length and about a single inch wide with a 14mm 6-point socket welded to the end of it at a 90 degree angle. I believe such a homemade socket wrench would be able to reach every nut and give you the leverage required to break it loose. That would take care of the biggest issue you face.

The last issue in removing the headers deals with the driver’s side. The steering shaft is in the way. So, you will need to take out the bottom bolt on the steering universal which is a 12mm. But before doing so, go steal some of the wife’s pink nail polish and paint a mark on the universal and the input shaft of the rack and pinion so that you can line it back up properly. You may also want to write a note and tape it to the door window to not touch the steering – I did. With the bottom universal bolt out, you will be able to lift the universal up and off of the input shaft and push it out of the way. You now have enough room to remove the header although you will find that for both sides, it takes a bit of twisting to find the “sweet spot” where they will come out at.

With everything now cleared out of the way, you can take a break and get ready for the fun of bolting in all of your new parts. I would recommend that you use new gaskets on every connection, including new engine to header gaskets. It is simply not work risking a leak to save a few dollars on gaskets. If you are going with a larger tube header, you may find it to be a tight fit on the driver’s side even with the steering shaft moved out of the way. In this case a little persuasion with a soft mallet might be needed. I would use either a touch of white grease or some anti-seize on the studs, either will work and it is doubtful that you will ever remove them again. The main thing is that you need a little lubricant on the threads, you also need to be very careful not to cross-thread the studs as you are putting them in place. Make sure that you can turn them 3-4 full turns before putting a wrench to them.

With the headers bolted up the next pieces are the high flow cats and all of the oxygen sensors. Sensors should get a touch of anti-seize lube – just make sure you do not get it on the sensor itself, that’s a death sentence for the sensor usually. With these pieces in place, you will want to put the x or h pipe in place. It can take a bit of wrangling to get it in place, but it will fit. It just doesn’t seem like it. By the way as I was putting these pieces in, I put the new gaskets in place and then just hand-tightened the nuts and bolts. This will allow you to align the exhaust system tips once you get to the back of the car. Overall the rest of the installation is rather straight forward. As I had unbolted all of the exhaust hangers when taking out the old system, a little WD-40 was used to slip the rubber hanger parts from the old system – it is much easier to do it with it laying on the ground that wrestling with each of them under the car.

We had to make a slight adjustment to one side to align the exhaust tips, but other than that I was able to tighten up all of the pipes and then fire it up. The entire system has a nice mellow sound at idle but is very aggressive as you get into the throttle. Off throttle, there is no rattle or popping sounds. I am very pleased with how the system turned out and you can certainly feel it in the seat a much better throttle response. I place that squarely on the headers and high-flow cats letting the engine breathe better.

A few pictures will be added shortly. They seem to have escaped me for the moment.


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