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I have never pulled an exhaust stud before while doing pipes. This evening I’m 4 for 4. These copper flanged nuts locked on the studs and there was 100% no getting them off without the studs coming with them.

Going back to using just regular nuts with 12mm flats. So much for trying to get the “right” part.

Edit to add details:


The nuts in question are commonly available and sold as exhaust nuts. I got mine from Auto Atlanta - but many places sell them. The have a copper color to them and the bore is slightly oval. The are designed to lock on to the stud - which I did not know at the time. They go on tight and you can not remove them without pulling the stud.

There are flanged nuts that work fine.

Kinda furious with myself right now.

Continuing to live life as an object lesson for others…

Zach

Did you use anti-seize?

High temp copper antiseize. The good stuff.
I had to put the studs in a vise to get the nuts off. They were locked on.

Zach

Doesn’t matter, they are a crush fit, for a stock vehicle don’t use them.

Car started popping a lot on decel today while I was driving around. So, exhaust leak. Once on the lift I found the #4 pipe had cracked at the ears.

Once I got the pipe down, the crack went 3/4 of the way around the entire circumference of the pipe! I was going to weld it, but it’s an older set of SSIs I got used. I don’t know that they are worth welding. Thoughts?

Zach

Tig is best, you need to flood the inside of the pipe with the shielding gas to prevent oxygen from attacking the weld.

Or

Headers and exhaust from Foley?

I eventually want heat. I drive too much in fall and winter before they lay down the salt.
But I am considering it. I know Joe would lend me his CFR header system if I asked since his car is under the knife.
Zach

I thought it had heat?

If you are jammed I will go take a look in the barn
Which side/version do you need?

1.7 or 2.0 liter boxes?
Remind me…which one curves up?

I have at least two spare sets…

Rich

1.7//1.8 curve up

There is an Aluminized Mercedes Benz flanged exhaust manifold nut that works great. They stay tight, but don't seize to the stud, and the flange means you can get a socket on them.

I don't have the part number but @partsguy22 will know.


Clay

Are those the VW style ones? With the slightly oval (that seizes the stud) hole? MOM on the stud helps.

I think you will find 8 of these more to your liking.

Im not a type 4 guy , But Ive seen more cracked SSI's than good ones...
In Fact I have a perfect set appearance wise.. and are cracked exactly as Zacs are..

Torqueing the shit out of the nuts, to cure a leak, is a sure fire way to tear the ears off. Take them up 5#s at a time, to 20#s, in an X pattern. You don’t want to build in a leak from the git go.

Those ACN 10mm flange nuts are the ticket! I use them for almost everything now

I learned the hard way with those copper nuts like 15 or so years ago. Not sure why vendors still sell them, they are the absolute worst

Are these what y'all are talking about?

https://vwparts.aircooled.net/ACN-Flanged-R...-p/acn-nuts.htm

yup @Rhodyguy has a bunch,, hit him up... I got 100 from him..

I always use a 1/4 inch mini-driver on the exhaust nuts to try and avoid this. All the used SSIs being old and heat cycled a million times does not help. And those fucking flanged pinch nuts are so tight that they throw the torque settings way off.

Lessons learned - a couple of them.

Zach

used the BMW version of these on my "6" headers ,really good and don't loosen up , got them from Pelican for chump change each,seem to remember brass and steel don't play well together due to constant heat cycling.
After extracting 4 bad head exhaust studs I wasn't prepared to use the wrong nuts..end of story.

Just curious…is there a mechanical issue with the studs coming out with the nuts? That happened on my car and I just put them back in like “bolts”.

I also used loctite 510 Hi temp sealant around the exhaust mating surfaces and it worked amazingly well…

The threads in the head are soft aluminum. They can strip out. You want to be able to leave the studs in place to preserve the head threads. When the heads strip out its a pain to fix them.

Zach

A MAJOR pain! Then you go shopping for step up studs, the drill bit and correct sized tap (that you may never need again). Heaven forbid you go too deep with the bit. The problem is the oval hole nut locking feature and potential seized up threads. MOM and the proper nuts. Name BRANDED nuts can cost a small fortune.

Years ago I had to have a head welded up the night before the MUSR so we could make the event. The car was running great, but on the way home from work, it spit an exhaust stud. The hole had been drilled and a step stud installed. This left the wall between the stud hole and the combustion chamber too thin. So it blew a hole from the combustion chamber to the hole for the stud.

I got home and immediately dropped the engine and pulled the head. I was pissed and in fix it mode. I took a still warm cylinder head to the local VW machinist (Lyle Cherry.. RIP) and he welded it up and re-machined it that evening. I took it back to the house and reassembled it. The next day we drove it to the event, and didn't have a single problem with the car the whole weekend.


I don't really like stepped studs or helicoil/timecert fixes. I feel there isn't enough meat on the heads to put them in safely.

These days, a set of new heads is the way to go. The current ones are 50+ years old and very questionable about what has been done to them over the years.

The nuts in question are commonly available and sold as exhaust nuts. I got mine from Auto Atlanta - but many places sell them. The have a copper color to them and the bore is slightly oval. The are designed to lock on to the stud - which I did not know at the time. They go on tight and you can not remove them without pulling the stud. Modified the first post of this thread. There are obviously some flanged nuts that work well. The ones I got that had the ovaled bore did NOT work out for me.

Zach

It's also important to watch that there's sufficient clearance below the ear at the head. With no clearance the load path wont produce crush on the copper sealing ring no matter how much torque you apply to these nuts.

Yup, those will turn out studs 100% of the time.

You're on it Zach, just regular nuts with washers works just fine.

Wish I had know this last weekend.

In a DM I said, and I would love to see, stub pipes.
So, modified and shortened SSI heat exchangers bolted to stub pipes.
This way we can get a firm and frankly better connection to the head, and create a much simpler way to remove the HE for engine drops.

That's a really good idea.

All the copper coated flange nuts that I’ve seen are prevailing torque, or locking, nuts, which will often cause the exhaust studs to back out. I run a tap through them. Non locking flange nuts are available, but harder to find, and not copper coated.

Is metal fatigue the question with 50+ years old aluminum?

I don't know about metal fatigue, but repeated welding of the heads can result in aluminum porosity.

A rather long winded explanation on Aluminum Porosity

And with our beloved little cars either approaching 50 years old or past it, it is safe to assume that the heads have more than likely been reworked in the past. And in the 1980s, they didn't have the technology to weld aluminum like they do now. It is possible some DAPO took a gas torch and a long stick of aluminum and welded them up in the past. We have absolutely no way to know 40 years later.

With the cost of new heads being almost the same as it takes to repair an old one, I will be buying replacements in the future for all of my build needs.

Hey @Rhodyguy , check your PM's I need to get some of these from you, thanks.

.

r not R.

That means there's two of you!

A pair of R/rhodyguys

Too funny

Was someone else messing with you?

Nope. Not that I’m aware of.