My recently acquired 2005 RX-8 has a rebuilt engine, but it seems like the shop that did the work was not very good, I'm finding lots of missing bolts. Also it appears they didn't bother reattaching the lower end of the AIR tube to the exhaust manifold, it's just dangling there. The car has a midpipe installed, and I'm not sure if there is anything inside the cat, so I don't know if I can just delete the AIR pump. In any case, the open hole in the manifold sound terrible and smokes a bit, so I'd like to reconnect the AIR tube.

The problem is that there is only one stud, and no nuts or gasket. It feels like it's probably a 10mm nut, but I couldn't thread one on by hand, and I didn't want to force it with a socket before I could get some confirmation that that is the correct size.

I'm looking for suggestions on the best way to proceed. If I can confirm that there is no cat I can put on a cover plate, but without two studs it seems like it's going to leak.

 

the studs are replaceable and can be purchased as can the nut. The nut is 10mm hex and I’m pretty sure that the stud/nut threads are M6-1.00. So you could possibly rig it short term with a short bolt. Long term would be an issue because on most street cars the heat results in a lot of corrosion. If a bolt seizes and shears it will be a big headache to fix. The solution is a nickel based anti-sieze applied to the threads, but that’s a specialty type that only a serious rotary enthusiast will have. A bolt will also be a lot harder to get in/out than a nut on an extended stud. So again, it could be a short term solution until you get the correct parts.
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Awesome, thanks for the details.

Can the stud be replaced with the engine in the car?

 

should be once you take the air supply tube off,

 

Part No. N3H1-13-456 STUD,EX.MANIFOLD $10.25 MSRP each

Part No. 9994-00-601* NUT,FLANGE $1.95 MSRP each

Part No. 13-996C N3H3-13-996 GASKET, A.C.V. $8.09 MSRP each

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Brilliant! Thanks again.
I've got it hanging on with one M6-1.00 hardware store nut for now. That helps tremendously with the noise and oil smoke under the hood, just a bit of an exhaust leak sound.
If I can resolve the other engine issues I'll order the correct hardware and get it set up properly.

 

New parts installed, easy job. Sounding much better now!
Thanks!

 

 

@AC0KG @TeamRX8 Hey guys. I have a similar issue where the stud towards the back of the car broke as the nut was being removed. It broke flush to the AIR tube. I'm wondering how to go about replacing this stud. Maybe even both. The other stud towards the front of the car has a rounded bolt on it. I now have a leak in this area due to the one stud breaking. I want to know how the studs are replaced. Do they just screw out? If they unscrew, what's the best way/tool to get them out? If not, how do I get them out? Also, did you replace yours with the header still attached to the car? Any help will be greatly appreciated.

 

Yep, the studs just screw into the manifold. I replaced mine with the car on jackstands, working from below. It's a tight spot to work in, so I certainly don't envy you having to extract a broken stud there, but as long as they don't break off too close to the manifold you can probably do it without taking anything else apart.

I may be telling you stuff you already know here, but FWIW:

Soak them in penetrating oil for a few days, then try a rounded nut removal socket for the front stud. If you're lucky the front one will come out of the manifold with the nut. If not, you can thread two nuts onto the end of the stud, tighten them against each other firmly to jamb them together, then use them like a bolt head to unscrew the stud (if you can't get enough torque you can add threadlocker to more firmly attach the nuts).

The broken rear one could be an issue if there are not enough threads left to get some jamb nuts onto it. If the penetrating oil does its work you may be able to grip the unthreaded part tightly enough with a good wrench to turn it. If there are enough threads to get one nut onto it you can either tack-weld the nut to the stud or use a die to tap a few more threads so you can fit a jamb nut on.

Work slowly and give the penetrating oil time to work. Warming up the area with a torch can help loosen things up too.

 

Just so we are clear here most penetrating oil is also very flammable and needs to be cleaned away before heating anything with a torch

 

@AC0KG Thanks for your reply! I took the entire header out along with the AIR tube that goes up into the engine bay then cut off the rounded bolt using a dremmel. Luckily, the block-off plate I was replacing the tube with is thinner and left some thread to tighten down a nut on each side.