trevorradman

oneslow55

Hate to say this but again ,this your install faults ..I know 4 people and one of them is making over 600 whp on it with zero clearance ,hitting or runing issues .That flAnge fyi is like that for a reason if you don't know why then look at the system and you should be able to figure out .They are a clone of arh and the even the arh clamps leak .Add some better clamps and some paste and your set.if you mounts are bad this will be many of your issues going on with rubbing and bugs happing..

GM_Lover

Went with OBX headers in large part due to this thread, so thanks. Really, really wanted to go with MBH (amazing quality), but they didn't respond to repeated emails and voicemails over the course of several weeks, and based on a brief search, I'm not the only one who experienced this. And this was pre-sale service.

Anyway, here's my input/experience relative to yours on these OBX headers:

1. The OE 10mm nut is definitely very difficult to thread and impossible with the header bolted down. It's also very difficult to tighten without rounding the nut. I had to take a wrench and shave off a lot of the meat on it to get it on the nut. A very good alternative might be to get a jetnut (say in 8mm or even 6mm hex) just for this one stud. Regardless, there's no reason the runner should slope down so quickly there. Definitely bad design.

JoeJErnst is absolutely right about using the OE flange off the OE h-pipe (with new gasket). For those who aren't familiar with it, the flange just slides off the h-pipe (no cutting required). I did this, and there's absolutely no leaks at this joint. Germans are smarter than us.

Like oneslow55 said, I had zero clearance or rubbing issues except for very, very slight kissing of the heat shield under the driver side door where the metal fuel lines run. I just bent in the heat shield very, very slightly to fix. Was amazed at fitment. I read about some earlier production AHR headers having clearance issues with the steering shaft, but the OBX ones I have have no such problems whatsoever. The production date of my headers was in mid-2015.

One thing I need to mention is that I replaced both engine mounts at the same time I installed the headers. The ones in the car had about 30k miles in them, but they were only collapsed about maybe 1/4". Thought about leaving them in since they were OEM Mercedes and the replacements were Corteco (who's the OE supplier) with a questionable cross-reference part number, but took the chance and replaced. Point is, if I'd left the slightly collapsed mounts in the car, these headers wouldn't have touched any heat shield and would've fit literally perfectly.

I agree. The clamps that come with the car are junk. I prepared for this by buying band clamps. It adds about $100 to the total cost, but band clamps + copper RTV (or exhaust paste) = zero leaks. I'm reluctant to have the system welded since it'd make it difficult to R&R the headers and rest of exhaust if needed. Definitely not a fan of the slip fit joints on the OBX either though since you have to be thoughtful about the order that you install the pipes (goes to your "Shouldn't have bolted headers in until I had all pipes set" comment). I'm considering just converting everything over to v-bands.

As far as the extensions for the rear O2's, I just picked up a couple of Bosch 15730 universal O2's. The length of these + the length of the stock rear O2's will give you way more than enough slack to connect everything up and route the wires in any way you see fit. Alternatively you could just use regular wire to accomplish the same thing. The O2 sensor wires looked like regular thin-strand wires, and they sell water-tight posi-tap connectors (although they cost $$$).

Overall, extremely happy with these headers. Would highly recommend them. My only fear is that the welds at the header flanges don't look the strongest, so we'll see how long they last.

trevorradman

Great info thanks for sharing! I will grab some universal 02s, still rocking a CEL Never heard of a jet nut, if that gives you the extra 1mm clearance, its a winner. There is definitely a design flaw. I will try a new gasket going to passenger side resonator as well, I was unfamiliar with the design.

Side note, I bumped a speed bump and knocked the headers free from the clamps, use caution if lowered... very loud, however has been extremely fun with open headers, sounds incredible at WOT, just too loud, makes babies cry.

GM_Lover

Haha. From what I can tell, my car is dropped about 1/2" from stock ride height (bought the car this way). Might be more. So I feel your pain! The cats on these headers make an already low hanging exhaust system that much lower. One of the main reasons I wanted to go with the MBH headers despite the $2500+ premium, but I didn't have the luxury of time (plus wasn't thrilled with their lack of communication as mentioned previously).

Car definitely sounds amazing though when it's loud. Agree 100%.

Simmelma

I have many of the same issues with my Project B5 headers, it seems they're all clones of each other lol.

I just purchased a set of MBH headers (Mike is a very busy man, I found that facebook messaging seemed to be the best method of contact), and I'm excited to experience the difference in quality. The sound of constant exhaust leaks has driven me to the brink of insanity.