Demon bolt slayed! (2022 update)
 

Just did my stock cat swap with my Berk HFC. And boy was this a tough DIY. Cracked those demon bolts like a boss. I feel like superman after this mod hah :happydance:

Don't see any newer recent posts with the 370z demon bolts so I might as well share my experience and hopefully give some tips to those who would like to tackle this as a DIY. And hopefully google search algorithms blesses this post for all to see in the future with ease.


To start I had a mate to help me out so an extra pair of hands really helps a lot. Doing this by yourself will be really hard. I don't recommend it. But even more power to you for doing it solo.

What I used with tools:

- 24" Breaker bar (milwaukee)
- trolley jack extension handle (extra leverage on top of breaker bar)
- 14mm deep impact
- 1/2" impact extensions x2 (or a 1-pce really long extension)
- 1/2" Impact drive gun (Milwaukee M18)
- 02 sensor socket kit or 22mm spanner (i chose to use the o2 sensor socket)
- 1/2" Uni joint socket impact
- CRC PENETR8, WD40, Chemtools rust breaking penetrant oil (or PB blaster for the US)
- Butane Torch (optional)
- A LOT of patience

What I did:
- Days before, i sprayed the F out of those 3 cat bolts to the header. Like doused in a pool of penetrant oil. Tried 3 types just for the heck of it!
- Also days before I drove the car to normal driving temp during work and let it cool down overnight whilst spraying some more onto the demon bolts

(Actual day)
- Let the car cool down.
- Sprayed some more WD-40/CRC.
- While waiting for the magic to happen with those demon bolts, We took off the intake pipe and box out for more space to work with.
- Took off the tower brace too just incase.
- jacked the car up at the front only.
- Removed both 02 sensors underneath including brace
- Get the extensions ready to see how many we needed. I ended up using 1 600mm long extension with 1 impact extension all 1/2" with no uni joint. We managed to align the extensions straight onto the demon bolts due to removing the intake parts.
- Started with using the impact gun with high torque low speed. Couple dagadagas to shake off the rust within the threads (atleast that's what we thought hah)
- Switched to the 24" Breaker bar with trolley jack handle. My mate kept firm pressure towards the demon bolt to ensure the 14mm socket won't move. I extended the handle as far as I could.
- Slowly applying loosening pressure. After 2-3 attempts they cracked. The most satisfying sound you'll ever hear.



Some pro tips I found along the way during this mod:

#1 Removing the intake pipe and box really gives you a tonne more space to work with. Def worth considering

#2 Use a impact 1/2" uni joint if you have to. And most importantly DO NOT let the 14mm socket slip or move while you are loosening. They will strip if that happens. We found on our RHD 370z that it is was quite easy without using a uni joint. LHD might be a different story. So just word of caution.

#3 One of the bolt holes on either side towards the header (behind the pre-cat o2 sensor) is threaded with a open ended screw bolt that you can take out with what looks like a e-torx socket fitting. We learnt this the hard way when trying to thread in the new nuts supplied by berk. The nut got rounded and stuck because of the condition of the threads and rust build up around it. Felt like an idiot not cleaning it up beforehand. We managed to get it out with a wrench and elbow grease work. Fitted the new nut and bolt after cleaning the threads with no issues after that. Why nissan chose to thread one of the cat to header bolts is beyond me.

#4 Grab a e-torx socket kit for above just in case. The size could be e10-e8. But don't take my word for it. Bring the whole set.

#5 To access the lower bolt out of the 3 you can either turn the wheel left or right or completely take them off. Just above the lower control arm is enough space to fit a wrench and 14mm socket or spanner if you've got the juice to crack em

#6 Mark the o2 sensors LEFT or RIGHT which side you took it off from. Just a good idea not to mix them up when putting them back. Wrap it up in a bag or something that won't damage the sensors in anyway. Heard they cost a fortune to replace if you f'd one of these up.

#7 You'll have to reuse 2 of the thread screw bolts from the old cats. Berk welded a fitting on both cats just for this to connect to the brace. They are tightened down by those 2 nuts you took off.

#8 Just be PATIENT! This really is key. I got frustrated a few times while doing this mod. If you rush something will always go wrong. So just take your time. Think clearly and take care to be safe.


This is one challenging DIY for sure. And I learnt quite abit after doing it myself with a mate. Hope this helps out more of you Z fam out there who want to take on the challenge and do the same thing. Peace!

Almost forgot. My Z sounds even better now. Can't wait to break it all in the next few weeks. :driving:

The berk soundnote is something I'll have to get used to. But It def sounds a lot more trumpety now. I love it!

Great write up! RepZ out to you!

Thank you good sir!

I've been searching for any info on a break in period for the Berk, or any high flow cats for that matter, and am having trouble finding anything concrete.

I am installing these as well, what is the break in procedure exactly?

Thank you for this great DIY

There is very little or minimal that you can do to "break in" a catalytic converter. Usually means a steady warm up, once they're up to temp and they start catalyzing that all there is too it.

Folks that say they've broken them in usually means for resonated components.

Breaking in resonated components means a sound change from exhaust soot/oil/gas coating the resonators as they age. Technically it should lower the sound a bit if it's intact. If it loudens then it means you killed some of the fiber/metal fibers inside the resonators.

Great write up and detail in your response. Biggest issue I dealt with was the 'frustration'..to your point...walked away...regroup and come back strong.

Well done my friend!

To those of you that have done this job, would cutting the cats off behind the flange be of any help? In other words, if you don’t damage the manifold’s flange, and don’t intend to reinstall the stock cats, can you make some room with a Sawzall?

That seems like an excessive amount of work and I do not know if it would help.

The demon bolt is accessed from the top but you'll need a swivel to get the correct angle. I used a 14mm 1/2in swivel socket, a bunch of extensions, and a 24in breaker bar. I might have even used a second universal swivel. The bolt head sheared off with very little effort. The swivels were Snap-on impact grade - the HF ones broke apart.

I was thinking with the whole cat out of the way, you could maybe get to the demon bolt from the bottom. Thanks for the info though.

There's not much to get to as it screws into a nut that is welded to the catalytic converter flange.