kens911

cleaning every thing up for reassembly and I realised that about half of the exhaust studs are broken off about where the barrel nut used to be and the ones that arent broken are much thinner at that point. I have new studs but having problems getting the old ones out. cranked on a couple of them with vice grips and they started to twist,instead of unscrew so i stopped. they are soaking overnight now with penetrating oil. Any one out there with a LOT of experience removing these that has any suggestions? and if i break any of them off flush how do you drill a steel stud out of aluminum without the bit drifting into the softer metal?

38D

If you break them off flush, take the car to a pro. There is a process which uses a copper electrode and burns the stud out of the head. You could try welding a nut on the end and then wrenching on the stud.

kens911

none are broke off flush (yet) by the way I Love the avatar

125shifter

I soak them with P oil, use MAP gas to heat the aluminum, and try to turn them out with sharp vise grips. If that doesn't work, I drill them at the machine shop at work or take them to an engine shop that's used to drilling them out. I've only resorted to a desintigrator when I've broken a drill bit in a hole.

kens911

is propane hot enough? would hate to melt the head

Rob S

I think what 38D is saying is this: find a specialized machine shop that does electrical disharge machinining (EDM). You can usually have them EDM'd out without a trace of damage to the head such that the original aluminum threads need no inserts. Once you've done that though, I'd recommend using stainless steel studs...

125shifter

I really think EDM is overkill. A half way decent machinist should be able to drill out a stud without damaging the threads.

MAP gas is hotter than propane. You'd have to use acetylene to melt the aluminum.

Rob S

David,

I think it depends on why the studs are broken off, and what you consider to be overkill. If they're badly corroded (which is usually why they've broken off), then it raises the difficulty of removal by any method. But with badly corroded head studs, the risk of nicking the aluminum threads with a drill goes up disproportionately. I recently paid $20 each to EDM out three studs, and absolutely no damage was done to the heads in the process. I think you'd have a hard time getting it done for much less by traditional machining methods. I'm just not willing to take the risk; I've seen so many hacked up heads from people who let their drill wander off center, only to make up for it with a big insert which is installed off center. Finding a vendor who will do EDM can be a challenge, but it's the only way I'll have it done.

nathanUK '81 930 G50

Rob, would they come out and do it under the car without removing the engine ?

125shifter

At $20 for 3, I'd go with EDM too. Since these are exhaust studs they're just steel not Dilavar so they'd drill pretty easy.

Tom F

Make sure the shop is good with the EDM. I had some done locally (Eastern Mass.) that were not too nice - they burned up some of the thread, too. I had better luck with a shop in Chicago, years ago.

I got better results having the machine shop drill out broken studs. I think that he uses a miller for better control over the drilling.

Rob S

I suppose there are hacker EDM shops too, but I haven't run across that yet. Nathan, I don't know about doing EDM with the engine in the car, but I have heard of the EDM process to remove exhaust studs with the engine assembled (but inverted and out of the car). I've only had it done it on bare heads.

m42racer

kens911

Rob S has given you some very sound advice. Are the heads and ther problem worth taking a risk. Follow his advice and have them EDM'ed out. Most places that do precision work will do this for you. Very easy work for them. Then do as Rob S suggests. Install Stainless studs and forget about them ever breaking again. If you need Stainless studs, email me and I will forward a place that has them. Long or short.

kens911

Well mt heads are off already most of them broke off flush I have ordered a tool that a guy on the pelican website uses so they can be drilled out without the drill wondering. should get it in a week or two will let you know how it works.