exhaust stud advice

dherrman · 06-27-2002, 04:44 PM

I have two bad studs, 2.0 motor. One is out and it looks like the po already widened the hole, but the insert is gone, the 8mm went in so maybe it was a 9mm rethread. the other is broken and it is in tight; motor is in the car; it looks like I can spend time under the car with this project; I would appreciate the best tips for removing the broken one, it broke right after the spacer on the heat exchanger; and what is the best thing for rethreading the other. Thanks in advance.

red-beard · red-beard's Garage

Go to your local F.L.A.P.S.

Drill out the threads and retap the exhaust to 10 mm. You can get exhaust stud that are 8mm on one side and 10mm on the other.

Ask me why I know....

James

Just don't break the tap off inside the hole!!! Use tap oil!

WOODPIE · 06-27-2002, 08:03 PM

Hello

I can give you a couple tips from my own experience, and I suggest you do a search and read up on this subject. At the very least, that will prepare you for "worst case scenario's", all more than likely to happen.

If I had my project to do all over again, I would drop the engine or better yet, pull the head off the engine. I think the heads can be removed with engine still in the car. If there is one "worst" position to be in, while trying to bust an exhaust stud loose, and then redrill and retap a hole exactly parallel to the adjoining stud, it would have to be a toss-up between "on your back" and "knees behind your ears". Much better to put the head in a position where you control it, rather than visa-versa.

That being said, on your broken stud, you are lucky, it sounds like; most folks are faced with studs broken off flush with the surrounding metal, and have no option but to drill a small hole in the center of the stud, try an E-Z Out, and when that snaps off, drill the E-Z Out, and the stud, out in progressive diametered steps, and then retap. You have at least a chance to gain purchase on the broken stud and coax it out using penetrating oil, heat, files, grinders, black magic and what-have-you. The heat would be applied to the surrounding metal of the head, so as to expand it, but no mere hand-held butane torch will impart enough therms to the metal to do much good. IIRC, an oxy-acetylene torch was used by at least one person, and with success.

When you get to drilling and tapping, I strongly suggest using LONG drill bits so the drill chuck does not interfere with the paralell course you want to direct it in. If the newly installed stud is flared wide, you will have trouble fitting the heat exchanger into position without damaging the stud threads. If the new stud is flared in towards the exhaust pipe, you will have a hard time threading the nut onto it and fitting a socket onto the nut will be impossible without grinding the socket wall down.

Last thing is, watch your depth, matey! Do not get over-zealous in the drilling part of this operation. My best guess for a safe depth of the stud hole is 10 mm, about .394" . As was suggested to me, (after the fact, unfortuately), wrap some tape around the drill bit you're using, at the proper depth, to prevent you from overshooting the mark.

You will find tap size information and options if you do the search, probably "exhaust studs" will do the trick.

When all your exhaust studs are replaced and repaired, use new copper exhaust head gaskets and new exhaust manifold nuts, plenty of high-temp anti-seize, and true-up the ends of the pipes to each other by using a large flat file.

Happy motoring,

Ed

dherrman · 06-28-2002, 02:45 AM

Thanks for the input; in the long run removing the head would likely be the safest and quickest way. Has anyone removed the head with the motor in the car; are there any tricks? I did search the archives and there was a lot there. There are those who have that method that works better than other methods; then again, figuring something out has its benefits. thanks for the help.

BenI · 06-28-2002, 07:31 AM

I've removed the heads before with the engine in the car. You have to lower the engine some to clear the suspension. DIsconnect everything from the engine and tranny, and remove the intake and cylinder tin from the side you're working from. Place the jack right before the engine/tranny joint, and lower it down. You can use the long all-thread to support/guide the engine as you lower it-get thin all-thread so it can bend as the slanted tranny mounts drop. I lowered mine just enough to remove the head. Things are pretty tight you can replace pistons and cylinders this way too. Good luck! email if you have any specific q's: benihas@hotmail.com

dman · dman's Garage

If you are not comfortable with drilling, tapping, E-Z outs (which are never easy) Helicoils and the works. Take the bad head off and bring it to a good machine shop, not necessarily an engine shop, and have them EDM it out. This just burns the stud out. They will also be able to Timesert or Helicoil the hole so you can use normal 8x8mm stud, instead of the hard to find 9x8 or 10x8 ones. This may cost a little more but then ruining a 2.0L head isn't cheap either. I have some expirience with bad heads broken studs/taps.

3D914 · 3D914's Garage

dherrman,

My only advice is don't use helicoils - go with the timecerts instead. They go in and don't come out like the helicoils are prone to do.

If you're looking for a cost effective tool to lower the engine, I notice that the local Checker had a cycle lift - good to 1500lbs for only $79.00. I bought a similar model for ATVs and its great for lowering the engine. You have to angle it slightly to clear the tranny at the back of the lift, but once clear of the car it makes a useful work stand ofr the engine as well. It lifts to over 24in.

Good luck,

dherrman · 07-02-2002, 05:22 AM

Thanks for the replies; I took the motor out, had a neighbor over who watched and drank our beer so it took longer than the usual 1.5 hours diy time; I used Kano lubricant x3 applications and the broken stud turned, so I lubed and turned very patiently and it came out; took it to a very good father/son machine shop in the area and they did a good job. Hopefully, the 5th will be a reinstall day and maybe I can drive it this weekend, assuming we have a quiet 4th here. I found a disassembled 77 911S for $2,500. Pricing out all it needs I am going to offer $600. Who knows, it could be one of those finds; I calculate that even with a motor rebuild at $600 I can top out at $6,500 which is the most I would pay for one in decent shape. Thanks again.