Stillen Headers + Berk HFCs self-install report

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.

Skorch

I think your post just completely turned me off the headers. I remember installing headers on my Tiburon, took me and my buddy 8 hours to do. I don't think I could go through that again, especially after your writeup. Thanks for a very thorough post.

wstar

Yeah it's hard for me to gauge the actual time we spent, as we were still finishing up the Scout project while working on the Z, it was spread over two days, and we took lots of breaks... but it was probably in the 8-ish hour range of actual time spent working on the Z. 2-3 hours of that probably could've been saved if it weren't for the O2 sensor issues.

However, I don't mean to turn anyone off of the headers completely. As I said, they look like they're really well made, and while I haven't fired the car up yet, I'm expecting I'm going to be extremely pleased with the final result. I'm just trying to turn people off from attempting a self-install. It's not worth it, IMHO. Let someone who does this sort of thing on this sort of car every day take care of it. This is a case where the shop labor charges are probably well worth it.

wstar

Here's a picture (sorry, crappy cellphone camera) of my front O2 sensors. You can see the one on the bottom with the destroyed threads and very rounded-off nut from all of the removal attempts. The threads on the other look better in the pic than they do in real life, they still need to be cleaned up if I were going to reuse them:

semtex

Thanks for the write-up! I remember with the 350, some guys said that they actually had to lift the engine out to get at the headers. I wonder if people will start doing that with the 370 as well. Definitely a huge PITA factor going on here!

__________________
"There are no small accidents on this circuit." -- Ayrton Senna
316.8whp & 248 ft/lbs (Dyno Dynamics) | 319whp & 256 ft/lbs (DynoJet) (04/23/10)
Stillen G3 CAI, CBE, Pulley / F.I. LTH / GTSpec Ladder Brace / Setrab Oil Cooler / UpRev-tuned by Forged Perf.

RCZ

And this officially means I'll be getting mine done by someone else. Its easier to sit in my office a few hours and make the money it will cost to install If I have to work either way, might as well be in an air conditioned office with a keyboard

JoeyD

^Word. I use to do all my own work. Once I had the concept of how everything went together and was sure I could do the work if I really needed to, I started paying people to do it. Especially with something as difficult as this it's worth it to pay up.

__________________
When was the last time you did 230MPH in something with 4 seats?

wstar

UPDATE:

I got the car back to Houston.

It turns out the front O2's are special order and take 5 business days, so I found an 18x1.5mm die and got some (crappy) threads working on the bad one so that I could reinstall the old O2s just for the drive home.

As far as remaining installation-related issues:

At first I couldn't figure out why my VDC kept disabling itself - turns out I didn't get the steering shaft lined up correctly when I put it back together. I thought I understood the markings, but apparently I did not . It was obvious once I noticed that going straight down the highway my steering wheel tilted 10 degrees to the left. It was easy to fix by just removing the front driver tire and unbolting the bottom of the steering joint through there and aligning it correctly. The purple lines on the bottom are meant to be aligned with the gap in the lower collar of the joint, not with the other lines up by the top shaft (this will make sense if you ever look at it).

Notably, the first time I fired it up after the install, there was noticeable smoke rising out of the engine bay area with the hood up. At first we thought this was a more serious leak at the header gaskets. However, it had an odd smell (more plasticy than exhausty), and after 5-10 miles of driving it had reduced significantly. By the time I got the car home, it wasn't there at all. Even on a cold start this morning, no more obvious smoke in the engine bay, so my theory now is that wasn't from an actual major leak of any kind. I'm guessing it was either the header<->cat gaskets supplied by Berk baking in, or the ceramic coating on the headers baking in, one of the two (or perhaps some kind of oil on the new cats from the factory?) Some kind of coating burning off somewhere in any case... Anyone familiar with that?

Other than that, just minor exhaust leak issues, which I kinda expected until I get everything retorqued a couple of times. No big plumes of smoke in the wrong places or anything, but under load you can definitely tell it's leaking (very raspy and ugly). I'm going to give it another 100 miles or so and then do the first re-torque on all the exhaust bolts that were messed with during the install, and see how it goes from there.

My butt dyno is pretty indeterminate at this time. The exhaust tone is a lot more "authoritative" (when it isn't rasping from the minor leaks), but it's hard for me to tell if there's any practical gain on the street so far. I suspect, as has been commented on in other threads, that my gains from the headers/cats will be somewhat neutered by the stock Y-pipe (and intakes for that matter) until I get the other, easier bolt-ons done.

K20A2_S

^^I'm curious and looking foward to seeing a dyno from a third party not related to a company dyno a 370 with

Intakes
Header, HFC, Y-pipe and stock or aftermarket exaust.

Will tuning be an issue with that setup? obviously it will optimize your mods, but is it necessary to keep the a/f at safe levels? I guess hookind up an a/f gauge tapped into teh header will be the only real way to tell....

wstar

I don't think it will be a "safety" issue from what I've heard (and observed so far), but I definitely do think a proper tune will be in order once all the major parts are on. My plan at the moment is Stillen's G3 intake, headers, and cat-back, with the Berk HFCs. However, right now only the headers and HFCs are installed. The car will be dyno'd and tuned once it's all in place.

I got under the car just now for the first time since getting back to Houston (with floor jacks, etc - what a pain ). I went ahead and retorqued what I could easily reach (basically everything but the actual header<->engine nuts), and found a couple that turned decently (half a turn on one, a bit more than a quarter on the other). Test drove it after, and much of the rasp is gone. What rasp is left now only kicks in under more demanding circumstances (full throttle or near to it and 5k+ rpms). Re-torquing the header bolts will probably get rid of the rest.

I also got my first good look at the cats during that, and the metal has discolored significantly now that it's been subjected to exhaust heat. They had a plain stainless steel color on install, they're now a deep burnt copper to also dark brownish all over. I expect this is normal, and that it probably explains the smoking during the first warmup. Someone let me know if you don't think so

Later in the weekend I'll probably team up with someone to have more jacks and jackstands available and get under there to retorque the header bolts.

(Oh, and with less annoying rasp I was willing to push the car a little further on this drive, and my patented Butt Dyno definitely now says it feels the difference, at least in the upper rpm range).

wstar

Final update on this. I've re-torqued everything and put in the new O2s. The header bolts were fine. The only bolts that really seemed like they needed a re-torque were the header<->cat flange bolts (I guess the gasket Berk supplies kinda burns in and gets thinner once heated). There are still a couple of points along the RPM range where I'm getting some rasp or vibration of some kind, but I've eliminated the possibility of any leaks. I think it's just the stock catback not coping so well with the new headers/cats. Other than when it hits those vibration points, it sounds awesome so far. I'm sure everything will get worlds better with the Stillen catback in place.

RCZ

Awesome, get us some sound clips man! I have my headers and catback coming in tomorrow, but I dont have a HFC, unless I order a set tomorrow..

wstar

Yeah I guess at some point it was time to get un-lazy and dig out my old mini-dv camcorder. I got some footage this morning, nothing spectacular. Will edit it in here once I get it cut up and uploaded somewhere.

RCZ

Youtube works great!

wstar

There you go, enjoy