Hi Guys,

I just went through this install this weekend. I searched a lot on here but never found a good description of the header installation process. (this may not be a good one either, but it worked for me) As I found out, the obx header requires some cutting and welding of the stock header pipe which has the cat mounted on it.

This is what I did:

Unplug the o2 sensors from the harness clips. Mine required loosening the drivers side forward heat shield in order to remove the 02 wires which were run between the heat shield and the chassis.

remove the stock header from the car

build a jig to hold the header in place, bolt the header to the jig at both ends



Cut the stock pipe just about an inch before the cat weld

Unbolt the header from the jig leaving the cat bolted to the jig

Slip the new header over the cat pipe (pipe diameter allows for the cat pipe to slide inside the tail of the new header)

Bolt the new header to the jig using the same holes

Weld the two together


remove from jig

Put the o2 sensors back in

Bolt the header and cat back into the car, first loosely at the cat/ cat-back, then tightly at the head, then back to the cat back connection to tighten

plug the o2 sensors back in to the harnesses

notes: it would have been really helpful to get the car higher in the air in order to remove and replace the header. It was very tight threading it above the sway bar. A little extra height helped a lot.

also helped me (a lot) to remove the cat-back support brace (6 bolts) in order to re-connect the header/cat to the
cat-back section.

I have never used a mig welder before, and this was the first time, with no help from anyone. I was a little nervous and did a sloppy job on the welds, but cleaned it up with a grinder and went back over it with the welder to hit a couple spots that I didn't seal up well the first time.

The butt-dyno likes it. The sound is really nice. Not too loud at all but a little more rasp for sure. My wife said it sounded sexy. To me it feels like it pulls much more willingly to redline and also the midrange feels better. I noticed at cruising speeds it seemed to like being in the mid 3k range better than before , if that makes any sense.

 

Nice Job! What kind of exhaust do you have after the Header and cat?

 

I just realized that you did not install the Ball and Socket flange!!! You just welded the header to the cat!!! There is no way for your system to flex/twist with engine torque . This may be a problem over time..

 

Yep, this is going to be a problem in the near future.

 

Ohhhhh. I wondered about that. I think I will make up a straight test pipe and put the ball and socket flange on it. there was not enough room to make that fit which I thought was strange.

Cat back is JCW by the way.

 

just drop a flex pipe in post cat before the flange. It will be fine.

 

The BSH Lower Engine Mount would be a great Mod to keep your engine from rocking. I installed one along with a powerflex transmission bushing after some wheel-hop caused the OEM engine upper mount to leak. My OBX header added some rattleing and although I do have some slight engine vibration with the mew engine/transmission mounts, the rattleing vibes are gone. Sorry to get a little off topic here.

 

great suggestions. thanks. not sure why I overlooked this detail. I was excited to get the part in, and excited about mig welding and next thing you know, it was done.

I made an appointment today at a nearby professional exhaust shop to have this flex joint added. In the meantime, i will leave the car parked so as not to break anything.

I have a pulley and sway bar to install while its down so no big deal.

 

Should look something like this......







OBX header is ceramic coated, and I swapped the hardware for stainless when I did the install.

Jim

 

any gains from the OBX header? didnt know that they were only around $170, thinking about purchasing with my injectors and cam

 

JimZ68 how much you cut from the stock cat pipe to weld the OBX attachment on ?
On the picture looks like you cut it right off .
Please confirm.
Thanks

 

Can't say for sure. The shop that did the work (Bay Bridge Motors in Oakland, Ca.)made up a jig to measure everything .

Jim

 

I just installed my OBX header with the stock Cat welded in.Not an easy job but not impossible.I found Bills web space very useful check this out http://www.billswebspace.com/MCSHeader.htm before doing the work .I had some challenges with the header screws ( cut one off ,removed the stud ) and the pre-Cat O2 sensor which I decided not to remove while under the car just disconnect it from the engine bay and removing after taking the old header out.
Just to let you now if you want to keep the stock Cat with the Obx header there is some cutting and welding to be done , you have to reduce the length of the flanged Cat to 32.5 cm therefore the attachment which come with the header need to be cut and the flange from the Cat needs to be removed and moved closer to the O2 sensor.The shop did this job for 100 bucks (Canada labour aint cheap )
The whole project cost me $350 and 5 hours of my work .Worth it ? Oh yess.
My mini gained some torque and HP and my custom made Catback sounds much better.
Thank you guys for sharing your experience.

P.S I changed the header because my preCat cracked all the way around .

 

Thanks for the info. I just ordered an OBX header due to the same problem you had. Clean break at the precat while on the highway. Did not make for an enjoyable end to my drive.