Hi, I'm in the middle of installing a Hurst short throw in my 94 C4. From reading the forum it seemed like dropping the exhaust was the way to go. However, I ran into problems with this since in the cars 18 or so year history the exhaust has probably never been taken off. I tried to be careful using heat and PB blaster but the bolt on top of the 3 bolt flange that connects to the cat (drivers side) snapped. I doesn't look like there is any easy way to get the stud out. Would I be ok just using the two lower studs that are still intact?

Any help is greatly appreciated. Thanks in advance.

 

Welcome to the club

Need to drill it out and put a bolt through it.
Won't seal otherwise.

 

Drill it out and put a bot thru it. Or drill it out a little over sized and put a over sized stud in it.

 

Thank you. I've learned a lot already from the forum.

I guess I'll try and remove the cat to gain access to drill it out. Although those bolts look pretty rusted too. Just hope I don't break one of those off as well.

 

Just had a look at where the cat bolts up to the headers and I'm almost positive those aren't going to come off with out breaking. The studs are so corroded there are no threads left.

Any other suggestions? I wonder if I can find a low profile drill or something somewhere so that I can do it while under the car.

 

Sometimes its faster and easier, to just cut them off, and drill, and fix them all, than to fight with it under the car. Not doing it properly the first time, means there will almost certainly be a second.

You'll be amazed how fast they come off with a sawzall. h

 

don't get too frustrated. heat and pb blast; heat and bees wax are all good, but may not be enough. I assume these are the studs that screw into the exhaust manifold? these buggers aren't easy, but, try a small grinder / dremel tool and grind off one flat of each remaining nut; if you watch carefully, you will be able to see when you've gotten through the nut and the stud threads become visible. Stop Grinding !!!
Use a chisel and hammer ahd smack the nut on each side of the ground portion,. this will spread the nut open ever so slightly and it will come off easily leaving the stud untouched.

as to the broken stud, it's not going to be as easy. Removing the manifold and working on it on a bench would be best but assuming you are going to try an on car repair, grind it as flat as you can to the manifold flang; CAREFULLY center punch it as close as possible to the center of the broken stud (you only get one real shot at doing this), take a small drill bit and drill into the stud; hopefully along its entire length on the centerline. At this point you can try more heat and PB Blast or bees wax; it should be more effective since it now can penetrate up into the manifold. continue with larger size drill bits until you can get an easy out driven into the hole and extract the broken stud.

if all else fails, continue drilling till you drill a 5/16th inch drill bit through the stud; 5/16th is the tap drill size for a 3/8 th inch national coarse tap; 3/8 ths N.C. is the same size / thread as the exhaust manifold stud. Use the tap slowly and carefully, with lots of oil and backing it out frequently to clear chips to avoid jamming, and potentially breaking the tap. Use a three tap set, starting tap, intermediate tap and bottoming tap.

Thread in a new stud and you should be good to go. To minimize future problem use lots of high temp anti seize on EVERYTHING and use brass or stainless steel nuts.

as to drills (technically drill motors) there are low profile ones available, but a right angle drill could what you need.

Once the exhaust system is out of the way, if you want to go further, using heat and LOTS of a PB Blast etc. on the remaing studs, vise grip pliers or a small eight inch (or so) pipe wrench can be used to TIGHTLY grip the old stud, and by PATIENTLY working it back and forth (never in just one direction) ever so slightly, it should break free.

Good luck.