wstar

Wanted to post my experience over the past couple of days here for you guys. I drove out Weds night to a friend's place out of town where we've got a well-equipped shop and a lift to work on a some projects, one of which was putting Stillen headers and Berk-Tech's HFCs in my 370Z. I just got back from the long weekend.

Just for perspective on this skill and equipment-wise, we had 3 guys out there working (myself included), and in the first two days we removed the body, engine, and transmission from an old Scout, mated the engine to a different transmission, then put the new engine+trans combo on a different frame and dropped the body back on and got it all running. Then we started on the Z...

The cat removal (and install later) is super easy, I think just about anyone can get that done pretty quickly with the right tools. As noted everywhere, the top bolt on the engine side of the cats is a PITA to remove torque-wise. penetrant (WD-40 or whatever) and/or heat (as in warm up the exhaust by running the engine) will go a long way in helping there. We still broke a bolt, but the broken bolt came out easy, and we were tossing those bolts for the ones that came with the new cats anyways.

Exhaust manifold removal and header installation on the other hand... Let me just say, when Stillen says on their website: "Installation should be done by a qualified mechanic with proper tools and a lift. This is not a backyard bolt on", they're not kidding. If you have any doubts about your ability to do this, please just take it to a shop and save yourself some pain. It's a real bitch. It was brutal, and I have the cuts and bruises and aches and pains to prove it. In the end, I think if I could redo things now, I'd pay someone else to do it instead.

Most of the issues fall into two categories: reaching the header bolts, and O2 sensor issues. Reaching all of the bolts during takeoff with sufficient force to break them loose was very rough. Getting the bolts back onto the new headers was even harder, but different (they give a little more room to work in general, but some bolts that a socket would get on easily before were now blocked by the routing of the tubes). In particular, re-installing the bottom center nut on the driver side is ridiculous. We ended up doing it with an arm wedged way up in there from below and a plain flat wrench a tiny bit of a turn at a time and then resetting the wrench, and it's a fair number of threads. The bolts were a pain, but it was doable and we did it. If we had had a 14mm GearWrench sort of thing, that would have helped immensely on that one bolt I think, although we might have had to cut the handle to fit it in there.

The problem that was responsible for the most pain though was the O2 sensors on the exhaust manifolds. I don't know what the factory did to those things, but you really shouldn't bet on getting them out alive. One of mine might be reusable, but the other is toast. With a properly-sized oxygen sensor socket (offset style), we were completely unable to remove them while the manifolds were on the car (they would actually move a bit at first, but then quickly lock up again before the first full turn was done). We opted to disconnect the cables up top and remove the manifolds with the O2 sensors still in them.

We mounted the manifolds in a large vise and tried everything (penetrant, heating the bung with a torch, using a massive breaker bar on the O2 sensor socket, etc...). On the first one, we actually broke the bung off at the weld and the threads still hadn't come loose, then had to cut the bung away from the sensor with a dremel tool. Looking at the destroyed threads after that, it seems the sensor+bung's threads were completely fused, although we're not sure whether we caused that during removal attempts. We had better luck (again outside the car on a vise, using heat, etc) with the second one and at least left some half-decent threads that could be cleaned up with a die.

As we were out in the boonies on a weekend, there was no way to buy new O2 sensors on the spot, so we just finished up the install without them and buttoned it all up and left it out there at the shop. I'm going to find some sensors here in Houston this week and run back out there and install them as soon as I can to finish this up, and then we'll actually get to see how the car runs.

Mostly I'm posting this now in hopes of saving others some pain. The biggest lessons learned are (1) If you have any doubts, pay someone to put the headers on, and (2) go ahead and buy yourself a pair of upper O2 sensors before you start the job, you can always return them unopened if you're lucky enough to not need them.

The headers themselves are well-made and look great, and I can't imagine anything Stillen could do to make the process any better (the O2 thing is all Nissan's fault, and the manifold bolts being a bitch are just the nature of the beast).

I'll follow up once I get the O2 sensors and get back out there and get this car back on the road.