Exhaust Stud Replacement

[Vincent Hill]

Have not been on the Forum for a While! Retired, Moved to Florida and restored 6 of my Motorcycles And Mini Cooper. Now it is time for the 1982 911sc. I have pulled the engine and transmission out because I think I need to replace the Cylinder Studs. I am also replacing the Entire Exhaust System with a Short Tube 316 Stainless System And use my 2 in 2 Out Muffler from Tasmania.

Removing the Exhaust was the normal deal with a few Studs Breaking and some Nut Splitting. Tried several different methods to remove the Studs from PB Blaster and Map Gas Torch to a Mix Of Acetone, Auto Trans Fluid always allowing an Overnight to soak and used Heat. Also used Roller Pin tools along with other Stud Removers And STILL Broke off every one of them I have now used a Thin Cut off Wheel on a Dremel Tool and have all of them Flush with the Cylinder Head.

My Plan is to Center Punch all of them and use a Drill Block to Drill then out (Maybe 1/8” Pilot Hole, then the 8 MM Hole and thread them to 10 x 1.25 to use Stainless TimeSerts.

I am at the Point where I can make all of the Right Decisions First and have no Regret.

My Questions are: Should I use Stainless TimeSerts and regular steel studs with Brass Nuts?

Steel TimeSerts, Stainless Studs And Brass Nuts or some other Combination Of Sert, Stud And Nut. What say the People that have “Been There and Done That”?

BTW, I have the Engine in a 360 Rotating Stand in my Garage with AC, TV and Plenty Of Light And I am Patient when I do my work

[Trackrash]

If you use one of those jigs designed for the task, you are half way there. If you are careful drilling, it is possible to remove the threads that remain without damaging the head.

I do not see the advantage of using time-serts.

Just replace the studs with stock. Then use LOTS of ANTI-SEIZE on the nuts when your replace your exhaust. Copper coated nuts will help as well.

[Vincent Hill]

Originally Posted by Trackrash

If you use one of those jigs designed for the task, you are half way there. If you are careful drilling, it is possible to remove the threads that remain without damaging the head.

I do not see the advantage of using time-serts.

Just replace the studs with stock. Then use LOTS of ANTI-SEIZE on the nuts when your replace your exhaust. Copper coated nuts will help as well.

I KNOW EXACTLY what you are saying. And yes being Straight is Key. Also I have had times where In the end all I had to do was “Push over” the Thread Shell And Lift the Remaining piece of Bolt. I feel the more you are careful the better your “Luck” is Also if I have everything ready for the worse case scenario the less I may need them.

Still saying that, I still want to use the Best Options so I will have the fewest long term problems so I can avoid going through this again. I do want to be able to remove the Exhaust System Without Problems in the Future And I think Stainless Studs are my best option.

[Richey]

If you are so patient , how did you break all the studs ? If it was me , I would take the head , cam tower assemblies off and have the studs EDM'd out , put in stainless studs and be done .

[otto_kretschmer]

why a timesert?

if you can drill a pilot hole in the stud, maybe with some kind of tool and bushing

you can slowly drill a hole into the stud big enough to use an easy-out

a helical insert (helicoil) won't need as much aluminum removed (smaller hole) and I would see this as a good thing

I would stick with stainless and avoid bronze inserts

this is a hot environment and stainless will do better

[Vincent Hill]

Originally Posted by Richey

If you are so patient , how did you break all the studs ? If it was me , I would take the head , cam tower assemblies off and have the studs EDM'd out , put in stainless studs and be done .

First, even though I lived for about 50 years in Washington DC (read a place where Every Government Agency has Letters For Everything like “LMD” large Mahogany Desk) I have ZERO Idea of what “EDM’d means😳

Yes, I am Retired, Have 9 Motorcycles, 2 Of Which I built from My own ideas (one I Raced in the Daytona 200 mile Road Race and the Other a few years back set a Landspeed Record right at 200 MPH) and I totally Rebuilt my 2.7 engine in our 1976 911s where I used TimeSerts and BigSerts to Save the Magnesium Cases Along with being the First person on the Pelican Board to install “Electric Power Steering” in a Porsche 911. So I would say I do have patience and a little skill and a Lot Of Experience. So yes when I looked at the Exhaust Studs that are 36 years old in a car that has been covered but sitting outside for at least 20 years and driven on Ice and snow covered roads treated with salt and Brine, I had very little Doubt that they may ALL BREAK OFF (from being Brittle, locktited in.

I did take a Week to try different techniques as I described then realized they were not coming out and to get on with removing them. Ok? Now that I am here, I was looking for advice from people that have been where I am and want to know what they did that worked best for them in the Long run.

[Vincent Hill]

Originally Posted by otto_kretschmer

why a timesert?

if you can drill a pilot hole in the stud, maybe with some kind of tool and bushing

you can slowly drill a hole into the stud big enough to use an easy-out

a helical insert (helicoil) won't need as much aluminum removed (smaller hole) and I would see this as a good thing

I would stick with stainless and avoid bronze inserts

this is a hot environment and stainless will do better

Thank you for your reply. The TimeSerts are Syncronised Solid Inserts That “Are” Slightly Larger (Helicoil 1.0 mm thick TimeSert 1.2 mm thick) but the Main Difference is there is no Chemistry between the Stud and the a Aluminum and the Stud must pull the Sert from the bottom vs the Helicoil is Every Thread for themselves.

Yes I plan to use Left hand Drill Bits once I get the Pilot holes Drilled and “Hope” that with the Reverse Pressure, the Heat And Oil (PB Blaster or the Mix) That they all will give up and come out. Saying that, and the fact that all of the Studs did break, I do not think I will have “100%” success Rate and for where the failures are I am looking at Plan B & C so I can order what I need now and not need to wait between Trials. Make sense?

[mepstein]

Stompski stud tool. Sold on Pelican. Works great.

[nocarrier]

Do you weld?

I'd Tig those puppies out.

You can also try mig/mag welding. Place a nut right over the stud and weld in the center of the nut.

I personally tig them out before I machine them out.

[piscator]

Discuss this with Steve Stomski! Stomski Racing sells time-serts and also a jig that makes drilling these studs, relatively, painless.

I had to drill four studs on my Porsche motor recently, so I may be able to offer some tips. Let me mention that I once worked maintaining printing presses and have drilled quite a few bolts out of steel side-frames, in situ, by eye.

But even with that experience, I purchased the Stomski jig and it was WELL worth it! Those exhaust studs are SMALL and without the jig you won’t find center consistently!

Buy carbide drill bits. The fluted bits cut more cleanly than twist drills, but either will do. I think you’ll need 3/16” and 17/64” but check. The Stomski kit comes with cadmium drills, but the carbide does a much better job and you’ve got a lot of studs to drill. Use PLENTY of the correct cutting oil! Don’t use PBBlaster or whatever substitute. You find drills and oil here:

https://www.victornet.com/aboutus.html

Once you get the bolts drilled and removed, clean the holes with a thread restorer. In some cases, you may need to use a tap; but try the thread restorer first. Use plenty of the correct oil!

This is not an easy job, even with the Stomski jig. But if you take your time and work calmly, you will get them all out. Maybe you can, but I couldn’t drill these by eye. I might succeed with a few, but I know I’d screw up a fair percentage.

All that said, if I had that many to drill, I’d look into giving it to a local machine shop.

[otto_kretschmer]

Originally Posted by Vincent Hill

I have ZERO Idea of what “EDM’d means😳

EDM electrical discharge machining

if you go with EDM I would take the heads off and take them to the machine shop

I question the use of Timecerts vs helicoil because removing the least amount of parent material may be important. I would have to take a good look at the head to see the edge distance between the hole and the edge of the part.

[Solamar]

I second (or third) the suggestion to take the heads to an EDM machine shop. The process electrically erodes the stud out leaving perfectly unharmed threads. Not terribly expensive either.

[boyt911sc]

Originally Posted by Vincent Hill

Vincent,

Why did you cut those exhaust studs? Do you realized that you made a simple exhaust studs replacement more difficult and tedious? This is my advise to you and you will surely regret if you do your exhaust stud replacement without using a jig. You can not make the 12 exhaust studs all correctly line up without the proper tooling.

And if you are thinking of installing a SSI in the future, the exhaust studs are critical and important to be properly lined up. Use or borrow an exhaust stud jig. Normally you like to have one exhaust stud to keep the jig properly line up. With both studs cut, the jig now requires more attention during drilling. Good luck.

Tony

[RedCoupe]

Originally Posted by nocarrier

Do you weld?

I'd Tig those puppies out.

You can also try mig/mag welding. Place a nut right over the stud and weld in the center of the nut.

I personally tig them out before I machine them out.

It amazing how well this works. The concentrated heat from the welder really helps break the bond to the head.

[Vincent Hill]

Originally Posted by piscator

Discuss this with Steve Stomski! Stomski Racing sells time-serts and also a jig that makes drilling these studs, relatively, painless.

I had to drill four studs on my Porsche motor recently, so I may be able to offer some tips. Let me mention that I once worked maintaining printing presses and have drilled quite a few bolts out of steel side-frames, in situ, by eye.

But even with that experience, I purchased the Stomski jig and it was WELL worth it! Those exhaust studs are SMALL and without the jig you won’t find center consistently!

Buy carbide drill bits. The fluted bits cut more cleanly than twist drills, but either will do. I think you’ll need 3/16” and 17/64” but check. The Stomski kit comes with cadmium drills, but the carbide does a much better job and you’ve got a lot of studs to drill. Use PLENTY of the correct cutting oil! Don’t use PBBlaster or whatever substitute. You find drills and oil here:

https://www.victornet.com/aboutus.html

Once you get the bolts drilled and removed, clean the holes with a thread restorer. In some cases, you may need to use a tap; but try the thread restorer first. Use plenty of the correct oil!

This is not an easy job, even with the Stomski jig. But if you take your time and work calmly, you will get them all out. Maybe you can, but I couldn’t drill these by eye. I might succeed with a few, but I know I’d screw up a fair percentage.

All that said, if I had that many to drill, I’d look into giving it to a local machine shop.

👍🏾👍🏾 Trust me I know the Difference between steel, Ti Coates and serious Carbide Drills. Also I have not only a Drill Block but a Tap Block so I can get the threads straight also. I had to make these when I was doing the 2.7 cases. So if I get to that, that will be what I am doing!

[Vincent Hill]

Originally Posted by boyt911sc

Vincent,

Why did you cut those exhaust studs? Do you realized that you made a simple exhaust studs replacement more difficult and tedious? This is my advise to you and you will surely regret if you do your exhaust stud replacement without using a jig. You can not make the 12 exhaust studs all correctly line up without the proper tooling.

And if you are thinking of installing a SSI in the future, the exhaust studs are critical and important to be properly lined up. Use or borrow an exhaust stud jig. Normally you like to have one exhaust stud to keep the jig properly line up. With both studs cut, the jig now requires more attention during drilling. Good luck.

Tony

I understand what you just said and makes total sense to me. My dad always said “Experience is always something you get Immediately AFTER You need it.” Yes if I had “1” Stud up and the Exhaust Fixture it would be easier to keep EVERYTHING Aligned. And I will now cut off one of the best flange on my old system so I still have this option. Thank you.

[Vincent Hill]

Originally Posted by RedCoupe

It amazing how well this works. The concentrated heat from the welder really helps break the bond to the head.

For a “FIRST” shot as what to do, a Damm good idea. I have a Mig and a TIG welder. And as you said, “All of that heat cannot be ignored! I do have a few questions on this.

First, since heat destroys the hardness or Heat Treatment Of Steel, Should I use Grade 12 or Grade 8 Nuts.

Second, what was your % Of Success?

My thought is, Welding the Nut will not Ruin my other Option! Thanks. 👍🏾👍🏾

[Vincent Hill]

Originally Posted by otto_kretschmer

EDM electrical discharge machining

if you go with EDM I would take the heads off and take them to the machine shop

I question the use of Timecerts vs helicoil because removing the least amount of parent material may be important. I would have to take a good look at the head to see the edge distance between the hole and the edge of the part.

Thanks, for my Something New today. Never ever heard of this. I know a place that does “Serious” Restorations. They have a machine shop and Work on Porsche, Ferrari and even Rolls Royce’s. Before I do “Anything” else, I am going to see them TODAY. I WILL Get back to here after I see them. If I cannot find EDM or not satisfied with what I hear, the TIG Welding Nuts in Place will be my next trial. I am going out to remove a few exhaust Flanges. Before I leave.

Thank you everyone I am now seeing what I thought I should see here! 👍🏾👍🏾

[nocarrier]

I have a machine shop and tig is my first weapon of choice.

One of my first jobs was working in the marine industry here in south Florida repairing impeller housings. They were held together with stainless studs in aluminum threads. You can imagine what happens when those two metals are exposed to salt water. Stainless will also work harden if your speeds and feeds aren't just right when drilling.

I'd say my success rate is in the upper 90 percentile.

When i use tig I don't use a nut. I just work the pedal and build up a "flag" . Basically something to just grab with a vise grip.

I'd use the nut with mig.

Heres a pic of some studs I removed recently.

I dont even know what filler I used. Just what ever piece of scrap that was laying on my table.

If I come across one that is being a bit stubborn. I'll grab the right filler rod.

If I were to choose to mig a nut on it would be the one closest to me.

[nocarrier]

Another tip

Once you get some weld built up or a nut welded on. Don't go gorilla twisting it right out.

Back it out slowly and if it moves give it a shot of some sort of liquid penetrating oil. Then twist back and forth to help work the oil into the threads while carefully twisting out a little bit at a time.

If it moves, you're pretty much golden.

Very important also. Make sure the ground is as close as possible to the stud you are welding.