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OBX 4-2-1 Header For '99 and '00 Miata

10K views 9 replies 9 participants last post by  FooSchnickens 
#1 ·
Latest OBX ? 4-2-1 For ?99 ?00 Experience

Just thought I would share my recent experience with the OBX 4-2-1 Stainless Header for ?99 and ?00 Miatas. I was ready to move away from my CA emissions set up and decided to try the OBX now that they offer a header that doesn?t require me to swap out my existing EGR tube. It does have the female fitting at the back of the header ? so your old 99/00 EGR will thread in.

I ordered the header from a west coast supplier ? and it took a bit more than a week to arrive using UPS ground. With shipping the unit cost was about $180, so not too expensive. Upon first inspection, the header looks great ? sturdy flange, nice welds, fairly robust pipes, and overall apparent nice build quality. There are no instructions on installation included ? only a warranty card enclosed.

I enlisted both e-mail and personal assistance from my friend and fellow Miata man, Larry. Let me tell you, it?s good to have friends when the job is big. He was a huge help from start to finish. So rule number one, have a smart friend to help you.

Removal of the stock exhaust and pre-cat etc was mostly uneventful. Use lots of whatever loosening chemical you prefer, and give ALL the bolts a good soaking. At Larry?s advice I did this the night before, and again about an hour before beginning the tear down stage. I used a breaker bar to help me remove the header bolts and all came off without too much fight. The bolts connecting to the down tube were another matter. They?re tough and nearly impossible to reach. But if you can get a wrench and an extension on them, it can be done. If I had it to do over again, I would have removed the down tube bolts before removing the header bolts. Just to make that area more solid to work with. Another bit of advice here. I later ended up with clearance issues during installation and recommend removal of the down tube bracket after the stock manifold and down tube are removed. That was another pain, but again soak them good give them time, and cheat when you have to with some kind of breaker bar. I also removed the EGR tube knowing that I would not be able to install the header with it ? and the end that threads into the exhaust manifold is stubborn, too.


Once the old came out, it was time for the new. Item of note. You may be wondering why I?m not talking about welding in a new bung for the O2 sensor that needs to be relocated. Well, we often remember the stuff that goes wrong on these jobs, but here?s one for the record books. Apparently the previous owner must have had a catalytic converter problem ? so the pipe had been replaced and sure enough, there was already a bung hole welded in right behind the primary cat. Just had to remove a threaded plug and I was set.

Long story short ? in order to get enough clearance for the header, Larry and I had to loosen the engine mount and jack up the engine. Some instructions or guidance from OBX on what they?d expect on install may have saved some trial and error that it took to get to this point. No matter ? that?s what it took to get the header into place. I used the O2 relocation kit from Goodwin Racing to save time and splicing work.. They worked perfectly. Once the header was in and O2 sensors in place, even with the down tube bracket removed from the transmission housing, the header rests against the ?body? side. It?s still rattling up a storm when I drive, so that still needs to be figured out ? assuming that?s my problem.

Now the EGR tube saga. Though the existing ?99 EGR did thread into the new header nicely, it did not match up to the studs on the intake manifold side ? not quite long enough to fit, but only off by probably 1/2 inch or less. We spent more than 2 hours trying to bend and stretch this tube to get the additional length required. Just couldn?t quite get there after numerous attempts. I sent Larry away with the tube to see his magician brother - and they got me closer still ? probably within ¼ inch with some serious heat with the torch and bending with welding gloves in hand. Bottom line though, the EGR tube didn?t fit which meant LOTS of attempts and bending and extending that didn?t really pan out. I ended up taking the car to my mechanic to get the tube bent and fitted into place. This was a very frustrating experience; thank heavens for valium.

Okay ? this story is getting pretty long, so let me get to my lessons learned.
1. Use lots of Liquid Wrench or whatever you like.
2. Use a breaker bar judiciously.
3. Have a friend help you
4. Have realistic expectations ? it will take time, and there will be times when your patience is tested!
5. Now the really tricky part. You need to decide if the cost savings of OBX is worth the time involved in working around fitment issues ? based on my sample of ONE. I have zero experience with the high end header products, so can?t comment on the installation process (jacking up engine etc.) but the EGR tube was a frustrating experience that took hours of effort before it was resolved ?professionally?.

I still have the issue of the header clearance and rattling under the car ? so there?s more to try to figure out. If I had it to do over, I may have considered a stock 2001+ system and a new EGR tube. I think costs would have been similar and I believe that I would have spent less time fighting problems with fit. Hope you all can learn from my experience.
 
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#4 ·
Yep, I heard a lot of problem with this OBX or Ebay type of header. Even if it fits, you'll find it hitting the trans tunnel...esp 6 speed.

Thats why got Maxim Works/ AutoExe header. They are top notch quality, one thing you notice that they have the bracket for the OEM bolt. So it won't rattle.

here's the pics after I got it HPC coated to reduce th under bonnet temp.

 
#6 ·
o my , that is a work of Art, u should post your own thread, to show that jewel off.

but in all honesty , that 4-1 obx for the 01 up fits better that the other ebay headers. no trans tunnel nothing, bolts right up to the Roadstersport midpipe.at half the price , cause lets face it, if i were fully decided to go all out na , then i would drop some money on a show piece like that Maxim, its the best.but my stock motor isnt going to know the difference
 
#9 ·
i got an OBX header on my NA and its been on for about 4 years know. Installation was easy and everything lined up perfectly except the O2 sensor. I just had to lengthen the wire. Quality is very good, and the finish is still great. i would buy this chinese product again. Does not have CARB certification but my car stills passes smog except for visual inspection'
 
#10 ·
It seems the 1.6 OBX headers have far fewer (if any) issues than the 1.8 headers. The most common issue is the contact you're experiencing against the transmission tunnel. The o2 location is a close second, but at least that doesn't require pounding with a 10lb sledge. And lastly is the EGR which you also ran into. Sometimes the pipe comes up short, others it overshoots the intake port.

Bottom line: If you're willing to put up with a little jury rigging to save a few bills, go for it.

I'm interested to see what these new $90 headers are going to be like that are popping up on ebay now.
 
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