M12 Metic Allen Bolts Downpipe bolts

[citymunky]

I'm looking to replace my Downpipe hex bolts with something easily like allen head bolts. The reason being the 3" downpipe is a PITA to install. It's maybe 1/4" after the flange the pipe turns into 3 inches, making it a pain to install. I can't use a socket because it doesn't fit, meaning I need to tighten those bolts with a wrench or crowsfoot 1/8" turn at a time.

Spec's M12x1.25 40mm

I tried Fastnal, Ace Hardware, Home Deport, Lowes, and none are to be found locally. I found some online M12x1.25x50 here https://www.belmetric.com/bsh12x125x50-allen-head-p-2087.html?cPath=6_339_362_365. Should I worry about seizing? Has anybody done this before?

 

[JNR]

You sure you'll be able to get a hex key (allen wrench) in there? I'm talking about either the long arm part (or the short arm part with tube extension), or else you probably won't be able to hold it enough to tighten the nut, or get enough torque to tighten the screw. They have the ball end hex keys which are nice so you can get it at a slight angle rather than dead on, but they are almost always on the long end, so you only have the short leg to turn.

I like hex socket screws myself and have replaced all sorts of hardware on the galant with them, but there are places I won't use them and this is probably one of them. Typically I use either a socket or T-handles and limit them to maybe max 10 mm screw, as the larger stuff just needs too much torque to be practical (some of them like to round out a little and/or a ball socket key doesn't get the same contact as a non-ball key.

Have you thought about welding a stud(s) onto either your downpipe or O2 housing, so you only need a nut? I don't know how your O2 housing is, but if it's like mine, it has threaded holes so the hardware (screw) comes up from underneath..sort of a PITA.

As for seizing, you should be fine with black oxide into stainless (I'm assuming threaded holes on O2 and it being SS) although doesn't hurt to put some copper (due to temps) anti-seize, but remember to deduct say 20% on your torque with anything like that on the threads.

 

[citymunky]

Hex key? No, no no, I have a set of Allen Key sockets. This will they can be torqued.

My downpipe is like yours being that the holes are threaded so the hardware comes up from underneath. Installing studs would leave me with the same problem of not being able to use a socket.

 

[JNR]

Allen is a trademark name and hex key (or bit socket) is the correct term for the tool /ubbthreads/images/graemlins/smile.gif No biggie, but just to be clear on what I meant...

I suppose you could drill out the threaded holes to thru holes and install the fine pitch stud onto the downpipe facing up (better to weld a hex bolt though, as the thru hole (or slot) will be too big for the stud and you'd have to be creative). I would think there would be more access to come from the top.

Another option and what I'm going to do is install my DP onto my O2, then fasten that to the turbo...there is some flex and rotation availble on my DP to make this a little easier.

 

[ktmrider]

Another option is to use wheel locks, good thread on this a few years back.

 

[citymunky]

I meant Hex Key as this

I know Allen is company that hex keys, its just like just calling any pair of locking plies...Vise-Grips.

 

[JNR]

Gotcha and yeah either one is fine of course...Like Coke I try to avoid asking for, as I prefer Pepsi if I'm going to have a cola /ubbthreads/images/graemlins/grin.gif

 

[citymunky]

Quoting JNR:

Another option and what I'm going to do is install my DP onto my O2, then fasten that to the turbo...there is some flex and rotation availble on my DP to make this a little easier.




This wouldn't work for me I don't have the space.



Quoting ktmrider:
Another option is to use wheel locks, good thread on this a few years back.



I'll have to look that up, but it makes sense since the diameter is the same (M12), and I have tons of thoese crappy "tuner" lugs nuts laying around.

 

[JNR]

^^Just don't lose the key! lol...

Yeah, that looks tight...I like the stud idea still, but you may have a hard time getting to the left (toward pass side) nut on/tightened from the top.

How about just using a long extension and/or flex extension with a conventional hex head, or is there not enough room between the extreme end of the hex and exhaust tube, for socket clearance? (maybe that's what you were talking about initially).

 

[citymunky]

"not enough room between the extreme end of the hex and exhaust tube, for socket clearance? (maybe that's what you were talking about initially)."

Yup this what I'm talking about.

 

[JNR]

btw - shoot this thread is reminding me of dreading doing this on mine soon...Going to remove the DP so I can fix the step in it (why can't aftermarket ever make something 100% right?) and at the same time weld on a nipple for my WG recirc plus clean it up and maybe put some wrap on the first part of it.

Anyhow, my DP has slotted holes and I'm wondering just how well it's going to line up (need to verify this) and I'm sort of tempted to put a couple locating dowels to be sure it's 100% centered; spent so much time porting, polishing and cleaning up everything else on the exhaust side, that's all I need is a little misalignment there.

Well, good luck on whatever you choose and remember you also have to loosen it too sometime.

As for these locks...do they have a threaded stud on the end? Trying to picture and the only ones I've seen/used are like lugnuts, or maybe thinking of something else.

 

[JNR]

Quoting citymunky:
"not enough room between the extreme end of the hex and exhaust tube, for socket clearance? (maybe that's what you were talking about initially)."

Yup this what I'm talking about.



Aaah, OK well perhaps the socket screw is your best bet...they do make hex head screws with a slightly smaller head, but not really common...they use them a lot for headers, but those are usually 3/8-16 or 10 mm thread, iirc.

 

[JNR]

Something like this, but in metric

 

[citymunky]

Quoting ktmrider:
Another option is to use wheel locks, good thread on this a few years back.



I found it

Solution for bolting a 3" downpipe to an O2 housing

 

[ktmrider]

^^ Boom good search, I couldn't find/remember it.

Spline drive is perfect plus like mentioned the whole stud is covered so less chance of seizing down the road.

 

[JNR]

But remember he's not using studs; needs a screw to come from the back side into the threaded O2 housing.

 

[citymunky]

Meaning I need to look into my random bolts bucket to see what I can.

 

[JNR]

Look online for the 12-point screws I linked above also, as they have a smaller head and take a smaller OD socket and can endure lots of torque; need a 12 point socket of course, but those are common.

 

[Terry Posten]

Here is the post I made years ago and is now in the How-to section.

Perfect solution to the down pipe fitmit issue.

click

 

[DynastyLCD]

know what else works good? an ARP head stud nut. thats what i use - fits my 3" downpipe perfectly.

OP: i had a similar problem, my o2 was just like yours and had slots and no threads. i took a 10x1.25 stud (2g exhaust manifold outside stud) and threaded it into a nut which i held (this was for the side closest to the turbo) and had the nut full of loctite. the other side uses a regular nut and bolt. if you use a lock washer on the downpipe side, and you have an impact gun, this will go together and stay together nicely. i've been running mine like that without issue so far!