Saturday 22 June 2019

Project Headers Part 2: BMW E92 M3 Headers Install

After the baseline dyno is set, it was time to tackle the install which will be done in my personal garage which I recently had a mini-split A/C unit installed. This is a must have in South Florida summer months to be able to work outside without sweating your balls off.

A short overview of tools you'll need to complete this install:

  • Engine brace (Dropping the front subframe is required)
  • Various sockets, wrenches and ratchets
  • Highly recommend 12mm stubby wrenches (short) and ratchet stubby wrenches for the header flange lower nuts
  • Highly recommend universal joints and wobble extensions, (Universal and/or 12mm for header nuts)
  • E-Trox, Torx, Hex/Allen bits
  • Torque wrench
  • Metal Saw or Cut-off tool (to notch under engine brace)

Overview of install. This is not meant as a step by step guide and this is not a very DIY friendly install, it is only for the more advance DIY'ers that have some decent suspension, exhaust experience. I would say this job is harder than a rod bearing install. Search M3post for my friend SYT_Shadow's DIY guide on rod bearings to give you an idea on how to lower the front sub frame which I will not be going into detail about.

  1. Remove all front under panels
  2. Lower front sub-frame (removing it completely is not a bad idea)
  3. Remove current mid-section (I left my mufflers hanging)
  4. Start by removing the header heat shields, there is very little space here, I do not have any pictures to show the location of the bolts but you should be able to see some of them, the ones on top are really hard to see/reach. I was not able to reach all of the bolts to remove the rear most shield so i remove what I could and just left it hanging and pushed it out of the way when needed  
  5. Remove header nuts, long wobble extensions and flex joints are very useful here. With the engine low enough you can get a 12mm socket on with a wobble extension on all of the nuts. It takes some clever maneuvering but it is possible to get all the nuts off this way.
  6. In order to remove the headers from their location I needed to undo the engine mount arms to get enough room. I can't remember if both sides were required but i did remove both, you might be able to force one of the sides out, but with the arms off it is fairly easy to snake out
  7. Ready to install the new headers, my experience was that I couldn't re-attach the engine mount arms with the headers mounted (They block off the upper bolts from being inserted) so I needed to attach the arms and torq the bolts before installing the headers, the new headers were able to fit in with the arms installed whereas I wouldn't get the factory ones off.
  8. Next, reinstall studs if any came off when removing the nuts (my experiences is this way is easier for the two lower middle nuts)
  9. The two hardest nuts to reach are the middle two lower ones. Here is where the short wrenches are needed, even with the short wrenches I was barely able to get a few fingers between the headers and block to hold the wrench and turn it a few degrees at a time. This part probably took me the most time to figure out, like 1 hour for these two nuts each side. I have no doubt some mechanics may give up and not even install these nuts but I didn't want any leaks and took the extra time to make sure I got them on.
  10. Note: Copper nuts are only hand tight in this picture, headers needed to be removed to fit the engine mount arm

  11. Finally after all the nuts are torqued, you can put the shields back on. I really wanted to reuse the stock heat shields but I can see some may leave them off. The driver side did require some bending but it went back in. There was a small piece of shield on one of the sides that I did not re-install.
  12. Next, now to assemble the xpipe. Fairly straight forward but the rear o2 sensors barely reach the bungs on the new xpipe. Luckily I had two e46 m3 rear o2 sensors laying around and one of them had the same plug has the e9x ones so I used that on the passenger side rear o2 which was slightly shorter. The driver side rear 02 sensor barely reached but it did, ideally o2 extension wires would be great but I just wanted to get these installed and I may return to add length and route the wires better later.
    • E46 M3 Pre-cat Cyl #1-3 (Bosch 13949) Oxygen sensor has the same connection but longer wires, I recommended these be used if you don't want to risk damaging wires or extending:
  13. with the 02 sensors installed you need to continue installing the xpipe pieces.  That's when you will hit the major hurdle and huge fitment problem with this part. One side is 2: inches too long 

  14. Only course of action is to cut 2" inches off the xpipe 
  15. With the exhaust in place, check fitment before torquing down all of the exhaust flanges. 
  16. Attach the subframe.
  17. Then it will come time to notch the under engine brace because if you don't, it will contact the header and prevent you from reinstalling it. 
  18. Install everything you removed, double check connections and you should be ready for the first fire up.

Next up, Dyno results: Part III: Dyno Results


  1. Hi. Thank you for detailed instructions. I would like to ask you two questions. Please do you know, if the left and right headers are same or they are designed little bit diferrent. My car is RHD, and if they are diferrent, there is big possibility to dont fit on my car. Second question is about back O2 sensor. Im sorry, my english not so good. Did you finally fit the originals there or need modification? Thank you.

    1. Hi Miro, I heard that there are no issues on RHD cars. So you should not have a problem there as a few have installed it on RHD cars.

      For the rear o2 sensor. The originals can work but the wires are stretched and could potentially damage by coming up from the attachment point above the transmission. To avoid that I do recommend extending the wires, or using O2 sensors with a longer wire. Otherwise you risk pulling the wires out and you'll have issues.


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