should I replace my exhaust studs or leave them alone?

[andyt11]

I have the engine stripped back to the block and heads. Two of the exhaust studs came out with the nut and the other ten are soaking in penetrating fluid. My intention is to remove them and replace with new hardware when the engine goes back together. (Its apart right now for valve guides / rod bolts etc etc...)

In the future, maybe one or two years, I might like to change the exhaust and I'm thinking it will be a lot easier if the hardware isn't 20 years old. On the other hand, I could just buy new nuts and put them on the studs.

I have the snap on removal tool and I have three or four days to soak them in fluid, but it''s crossing my mind that it could be a waste of time and a recipe for trouble. The shop where the engine is going has an edm machine if I snap one off but like I said, I'm wondering if there is any point. What would you guys do?

Car is an 88 3.2. Exhaust is stock and original. Looks like something from the titanic. Very rusty, will get another few years out of it though.

Any thoughts appreciated.

[porschenut]

I'm certainly no expert, but if it were me I'd just clean up the threads on the existing studs, and reinstall with new nuts and anti-seize.

[Daviboy]

Based on personal experience I would replace as much as I could now while the heads are out the car. If you wait you will need to strip down again if any dont want to come out....

[MBruns]

Its risky, more so it seems when you are not taking it apart completely, even with the heads on the bench and blasted using a torch 50% usually break off flush, my position has been if the come out with a simple double nut and some blaster fine, if not leave them be if they are OK.
Mike Bruns JBRacing.com

[Grady Clay]

Replace them.

With care (and luck) you won’t break any.
If you do, having the engine on the stand makes the extraction of the broken stud remnants relatively easy.
Yes, not as easy as when you have the heads in your hands.
(Very difficult in the 911.)

It is useful long-term service to remove the exhaust occasionally (before rust makes it difficult).
Cleaning, painting, new hardware and gaskets keep things looking new and extend the life of expensive heat exchangers, catalytic converter and muffler.

Best,
Grady

[tadd]

Pull them and spend a little coin and get the special alloy ones here are pelican.

Broken studs with a full engine in the car sucks .

t

[Jesse16]

Careful if you take the advice on the "fancy alloy" ones. They are not the correct length for your car if you have the thick exhaust flanges. (ask me how I know) You have to make sure you buy the correct "length". Don't assume the length if it isn't stated. I also found that my "new" exhaust gaskets are 1mm thicker than what came off so that adds height. By the way, I'm making my own studs from a stick of threaded alloy rod, hope it works out. They sent me an extra 1M rod by mistake so I have enough material to make about 2 extra engines worth.

[andyt11]

Originally Posted by Grady Clay

It is useful long-term service to remove the exhaust occasionally (before rust makes it difficult).

Best,
Grady

Thats how I feel about it. Right now its on the stand. I can get to it easily and work comfortably. In a couple of years when I want a new exhaust, the swap will be made a lot easier if I have relativley new hardware.

I'll see how it goes. Any that are super stubborn can be left for my mechanic to take care of. Just trying to save myself a little loot.

[KTL]

You got lucky that you didn't break any of them. If you're not going to torch the remaining nuts off (cherry red with the ox-acetylene "blue wrench"), i'd consider cutting them and trying to split them instead of relying on the penetrating lube.

I agree with the periodic removal approach. Once I got mine off, cleaned the threads and used a good dose of anti-seize, I have since made it a point to crack the nuts loose and re-tighten on occasion. I was lucky with my car that it's a rust free car with little foul weather use and even mine were tough to get off. Other friends with much more weathering were not as lucky and had to drill out broken studs.

We're fortunate nowadays with the nice drilling jigs that some of the contributors on this board joined in to make and sell to a wider audience via Pelican. A drill jig makes the repair a lot less painful and nearly always avoids the need to use a thread-sert or helicoil. I believe it was John Walker and A Quiet Boom who got together (amongst other people i'm forgetting) and perfected the drill jig for all the 911 port sizes.

[shrtshck]

I asked the machine shop to remove the old exhaust studs when they did the valve job. After the machinist finished I asked him how it went, said he has removed many studs in his day (guess he is mid 50s) and these rated among the toughest. Ended up having to insert a couple. I'm ever so glad that I didn't set out to do it on my own.
If the heads are off, by all means replace the studs, much easier to deal with problem studs when they are on the bench.

[Neilk]

I got lucky as hell with my studs. When I took the heat exchangers off, about half the studs came out with the nuts and half unscrewed normally. No heat or any prep work. My engine had apparently been resealed 20 years ago.

Since the whole engine was coming apart due to some pulled head studs, I started slowly one by one and soon enough, they were all out without any issues.

[andyt11]

I'm going to soak them for three or four days and give them a try with the snap on tool. If they don't come I'll let the shop deal with it. If they break them they have an EDM machine amongst other equipment. They can deal with it.

On another note, am I right in thinking anti seize on the end that goes in the head would be a mistake? Copper and Alu? Might it bind harder? When it comes time to install new studs, I'm thinking thread lock on the end that goes in the head and anti seize on the nut end. Is there any official line on this?

[ajwans]

Here's another thread which is related to this:

Where to buy Si/Br nuts? (for exhaust)

The nuts in question can be found here:

BMW E21 Cylinder Head & Valvetrain - Page 4

andy