Cat got stolen, looking for advice.
 

After the catalytic converter got snatched last month i bought a new one + muffler from ebay but when i tried to mount it i came across a problem..
I've broken off the studs holding the old cat (or what's left of it) to the exhaust manifold.
Now i'm contemplating taking off the manifold so i can go to town on the remainder of the cat with an angle grinder and then drill out the studs from the manifold.

I'm just wondering if that's even possible without lifting the engine?
I also can't really lift the vehicle except for maybe 40-50cm (on jack stands), and about 1m of cat pipe is still attached.
And i don't want to break off the engine block studs, not sure if that's common? The nuts don't look rusted.

Maybe i should go see a real mechanic? lol
Any thoughts? Thanks.

I think a real mechanic is a good idea.

The manifold nuts at the head are copper, so they shouldn’t be rusty. The studs may be rusty but soaking them with penetrating oil will help. I always get new studs and nuts, or nuts at least and chase the stud threads with a die if I’m reusing them. New gasket goes without saying, but, I just said it.

Get what’s left off the car and on the bench so you can work on it. You’ll have to fit up everything on the car, unless you bought OEM parts. Leave all bolts loose until it’s all in and on the hangers. Then start tightening bolts.

Hey Jim, thanks for the reply.

The nuts at the head seem very clean, but they don't look like copper to me. (i have only looked at them from underneath the car though so maybe they've discolored, not sure how long they've been on there)

I've got some WD40 and the gaskets + new nuts are not a problem, what i'm scared of is:
A) stud(s) breaking off
B) that i have to get the head off to get the manifold out.

Anyways, i'm gonna see a mechanic first and ask what they want to charge for it.

If the nuts ARE copper, they will (worst case) strip on the rusty steel studs.

Once they are off/apart, use a pipe wrench to get the old studs out and install new ones.

Unless, they are not TOO bad, then just chase the threads with a die. Apply never-sieze to the studs before securing with the new nuts (and new gasket!)

It's been so long since I've looked at the 4-cylinder maybe they did use steel nuts at the head...

The part# for the head nuts is 11721437202 and a quick google image search tells me they should be copper.
But on my car, the nuts on the manifold to catalytic converter section were steel nuts and those are supposed to be copper too (18301737774).
Not sure if those were installed by BMW or a previous owner, i suspect the latter.

Probably the latter.

I would plan / budget to replace all the hardware and hangars. Most likely there will be other "improvements" you haven't discovered yet.

When I work on my Land-Rover, I always buy way more stuff than I think I'll need, including fasteners. Then, I just return what I didn't end up actually neededing.

I hate getting knee-deep into a job and have to stop because I'm missing a bolt or gasket...