Can anyone confirm the torque figures for the heat exchanger to head nuts? I have initial torque at 7.3 ft/lb and final torque at 24.5 ft/lb.

Too late tonight to look it up and someone will get it for u. Get a Haynes book. Has (almost) all the torques.

The torque value is not printed anywhere. Use only the minimum torque to get them to seal, its too easy to strip the studs if overtightened. Are your coppper exhaust gaskets annealed...very important to do.

Start low and tighten gradually. I prgressively tighten them, test them, then let them cool before tightening some more. Mine ended up at 14 ft-lbs to get a seal.

Thanks Jeff, I also could not find the torque value anywhere. I got the above listed figures from a vende. The value seemed high for a 8mm stud. I have annealed the sealing rings, put anti seize on the studs and dressed (flattened) the sealing surfaces of the stub pipes.

I will take your advice in torqueing them down

For a bus they give it 16 (oops, 14 )foot lbs. They are known to loosen so it's recommended to re-torque them after running it once.

dbl posted

I just went through this entire process:

1 - replaced all exhaust studs (Manufactured my own 8mm studs before removing the old and found out that all of my stud holes had been tapped out to 9mm).
2 - ordered new 9X8mm step studs from www.belmetric.com
3 - extracted all old studs with stud extractor tool from Sears ( the kind that pound on over the studs and acts like a bolt head)
4 - Installed all new studs to find that they all have a slight bend to them, so they need to be clocked right or the HE dont fit over them
5 - threw aside the stupid copper plated exhaust nuts from pelican parts because the flange on the bottom of the nut would not clear the side of the HE stubs. (actually accidentally bought TWO whole bags of them - anybody want some?)
6 - Bought 8mm "JIS Nuts" from Ace. They are smaller barrels so a 12mm socket will fit.
7 - Used SS washers under nuts (some had to be ground to fit in the small space)
8 - STILL had to grind off the side of a 12mm 6 point socket to have enough clearance from the side of the HE for the socket to fit down.
9- torqued all nuts to 14 ft-lbs
10- installed second set of nuts to lock the first set in place.

If I could have found SS JIS nuts, I would have used those.

HTH - Stu

It is debatable, but stainless exhaust hardware is probably not as good as regular steel. Stainless expands more with heat so they are more likely to loosen over time. It can gall both itself or regular steel more easily. Also, unless you use ARP nuts, typical stainless nuts are probably equivalent to grade 3 .

The problem with using 2 nuts on an exhaust stud is that you can't reach the 'inner' one to hold it from turning taking the exhaust off, and the 'outer' one will want too drag it, ruining the stud thread.

By using anti-seize on the threads, you have now made the dry torque figures no longer applicable. Google wet versus dry torque numbers to understand. Example, a dry torque required of 20 ftlbs being applied to a wet thread will yield about 25-28 ftlbs of actual torque, resulting in an over-torqued fastener.
Better yet, just do as Jeff said and torque only until the HE's seal.
Tom

Last time I did this I used McMark's patented reverse shop vac procedure. I taped the "Blow" source to my tailpipe and hunted leaks with a feather under the car. Worked like a charm. Very controllable and no heat to deal with. I'd recommend trying it.

Oh, I love that. My shop vac doesn't have a 'blow' function but I suppose I could use the out-let or compressed air...Nice tip!

I like that tip also, very smart

I always wondered about that. Things that make you go Hmmmmm.

I too use anti-seize. But I'm more like Jeff, I do it by feel.
I use a 1/4" torque wrench and start at 10, then 12, then 14. But I'm focused on the the feel not the click. But I guess I don't really know what I end up with.

The first time I backed a stud out of the 3.2 in my 911 it scared the crap out of me.
I've used anti-seize every sense.

Maybe I'll stop by Rothsport and pick Jeff's brain on the anti-seized exhuast nut torqued value.

Thought I'd toss in a find, I too just went through this and replaced a few of my exhaust studs. I knew the size I needed for stock but couldn't find it until I happened to stumble across the perfect size, thread and length right off the rack at auto zone. It seems a 96-2006 Lincoln uses the same size we do. Plus, you can use a 3mm (I think) socket to set them in place.

How do you anneal them?
In the stove oven?
What temp and how long?

I did find this...
http://www.tunacan.net/t4/reference/torque.htm

Shows heat exchanger/head torque at 16 Ft/lbs

As far as annealing the gaskets, just heat them with a propane torch until you see the color change. Move the flame to move the color change around the whole thing. it goes pretty quick.

Or you can use a rubber tailpipe plug with a schrader valve in it and blow in a few pounds of compressed air.

Why do you anneal? What does Annealing do to the seal rings? I installed the last set cold and drove 15,000 miles with no leaks. Is it just insurance of a good fit or what? No reason not to do it if it's better. Advice welcome.

Annealing makes the copper "dead soft". In theory, that allows it to conform to the area that it is sealing better. I'm not sure how much good it does in practice, but it's a pretty simple extra step that shouldn't do any harm...

--DD

Of course it does. stick the vacuum hose in the other (exhaust) hole.

I've seen a thread where the guy took a long flat metal file and ran it across both pipes at the same time, where they mated to the head, to get the 2 pipes of each side's HE to be perfectly flat. the flatter key are, the less torque, I assume they'd need. I wish we had a way to view all photos ever uploaded.

light, even dressing with a big bastard file is pretty important. a file big enough to do both pipes on one side at a time. black sharpie the top edges of the piping and be gentle with the back and forth. just enough to remove the ink. i take the fasteners up 5lbs at a time in a cross pattern.

k

Also, you have to take off a much from the tops of the bolt collars as you take off the mating surface on the flanges - there's only so much crush before they bottom out.

usually the first pass with the file shows how much material you'll wind up removing. hence the delicate touch.