Are brass nuts strong enough for a exhaust manifold - Tablot Express(84) 2 ltre.

Are brass nuts strong enough for a exhaust manifold - Tablot Express(84)2 ltre.
My dad and I have been replacinging a blowing exhaust manifold gasket
on a Tablot Express (84).
He was given a brass set of nuts which he was told would be OK (even though the original were steel) for an exahaust manifold. We found that the nuts are not strong enough and strip and seem to get 'drawn' into the manilfold stud holes. They have prevented us (so far) to be able to tighten the manifold to stop further leaks.
Q1. Are brass nuts strong enough and suitable for an OLDER engine? How do they compare to steel grades?
Q2. Can brass nuts be as strong as steel? Are they graded like steel?
Q3. I think the exhaust manfold has been changed before. Should it have washers with the nuts and what torque should be used?
Q4. Any web page which gives the pro and cons of different types of nuts, there strengths (grades and torque etc) and the material they are made from?
Chris.....
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Chris Wilkins wrote:

They are not as strong, but they have been used for years.

No and I don't believe so, although my FLAPS sells brass nuts specifically marked as "manifold nuts" so they ought to be suitable for the purpose.

I believe so and check your shop manual. Torque will depend on the size of fasteners used.

I'm envisioning a flat flange type connection with studs and brass nuts used to hold the downpipe onto the manifold. I imagine if this is the case that it's not so much a torque issue as something isn't lining up correctly. You may have to heat and tweak the downpipe a little to get a leak free seal. Also pay attention to the mating surfaces - if there's any rust scale built up on either one you may have a persistant leaking problem that won't go away until the surfaces are trued.
I'd be hesitant to use anything but brass simply due to the possibility of corrosion or galling. If you're absolutely stuck and find you just need extra torque to completely get rid of the leak, you might want to try stainless steel nuts, but you will need to use an anti-seize compound on the stud threads or you will never get them off again. I'd highly discourage you from using regular grade 5 (or 8.8, since you seem to be talking about a Yurrupeon car) nuts as they will rust almost instantly in that high heat environment, and not only will they become one with the studs, they will actually "shrink" as the outside rusts and disintegrates (necessitating such drastic measures as hammering a smaller size metric socket on a SAE nut or vice versa, lots of heat, possibly sacrificing the studs to get the connection apart down the road.)
good luck
nate
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use stainless bolts/nuts and nickel antisieze - stainless bolts are graded too - use better than 5 - I've got 316 grade 12 in my exhaust systems (manifold to exit), can take em on and off with ease
Andrew
Nathan Nagel wrote:

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the aircraft industry uses brass nuts on exhaust systems. use anti-sieze goop too. sam
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Stainless nuts can gall onto to steel studs, and they will basically never come off, thought the nickle anti-sieze makes that a possibility only a few years down the road.
I use brass or bronze nuts on manifold studs by preference. the manifold has to actually fit, you can't bend it into place by over-torquing.
Brian

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Ummm, brass exhaust header to pipe nuts are all I will use specifically because they sure don't 'seem' to have the galvanic effect and can still turn off when there isn't anything left on the outside due to corrosion to get a wrench on. A pair of vise grips will still spin off corroded brass nuts.
If they are stripping on the OP, then he needs to buy a torque wrench.
If they are properly torqued, they won't strip or dig in, well they freaking 'can't' dig in because the manifold studs or bolts all need manifold washers.
Now if he is trying to put it together without manifold washers, it will never work, steel or brass, no matter.
Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's
Bush wrote:

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Q3...
Yes, you have to have manifold washers. No nut will work without them.
Yes it needs to be torqued and in a certain pattern or it will never seal.
Q2- Yes brass is the 'best' way to go.
Buy a cheapie Haynes manual for twenty bucks, it gives all the torque specs and tightening sequence for everything on the vehicle.
Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's
Chris Wilkins wrote:

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I own a 1980 Fiat Spider which I turbocharged. The main issue regarding the turbo system has been the exhaust nuts staying torqued. I think this is also why the car had been blowing exhaust gaskets.
The typical split style lock washers were not holding up. I finally found something that seems to work.
I've been using these things called Nord-Locks. They are made in Sweden and are not sold everywhere in the United States so I have to get them through mail order but are so good they should make the split style obsolete. I'm sure you can find them in the UK.
http://www.nord-lock.com /
They have these little steps inside that lock in place when torqued. The interesting thing is if you tighten a wingnut with your fingers it takes more pressure to unscrew the nut.
So far I've put about 1000 miles on my turbo system since I tore it down last winter to make some repairs. I've had to tighten a few nuts a second time just a hair but so far not a third time. So they seem to be doing great.
Also I don't know how many people would recommend this but I did it. On the opposite end of the stud that doesn't have a nut (such as the end that screws into the cylidner head) I put antiseize compound on that end but the other end that the nut contacts I deleted the antiseize compound. My theory is there are situations where you actually want the nut to seize. Like on problematic exhaust nuts. I figure if I have to remove the nut, at least I can back the stud out if the nut is seized.
Also this debate will go on forever but I chose grade 8 steel on all my exhaust fasteners. Some turbo guys recommend stainless steel but they mention nothing about it being bad to gaul. They say grade 8 isn't strong enough to use on turbo systems. Well I work in the chemical industry and my company has been in business for 80+ years and we never use SS on anything that get's hot for this reason. Also Chrysler used grade 8 on their turbocharged engines so I don't know why people think SS is better.
As far as using brass nuts. Well I can't say. I've never heard of using brass exhaust nuts. But would think they wouldn't be good on anything that gets hot.
I would have the surface of the exhaust manifold checked to make sure it's not warped. This will cause the gasket to blow.
Can't help you on the torque specs. Although there was a Talbot built during those years that has a copy of the Plymouth Horizon/Dodge Omni. The body shell is the same but the grill, taillights and dashboard are different. I don't know if they use Chrysler engines or not.
Hope this helps.
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I will second your conclusions. SS nuts are not as strong as grade 8. Nord-lock is a great product to prevent loosening. I played around with one. I used stage-8 reuseable fasteners, and they work great too. Next time, I will use the nord-lock because is cheaper and faster. You could get the nord-lock in the US through McMaster Carr. It is a good idea to put anti seize on the stud part that goes into the block, and not on the nut part. If the nut is not turning, it would be impossible for the stud to loosen by itself, so putting antiseize on half the stud is a great idea. I will use that next time as well. Another reason not to put antiseize on the nut part is that you will change your clamping force on the nut. Antiseize could put way more clamping force on the cylinder head that is specified in the manual. I stripped out the threads on my 22RE cylinder head that way. See: http://home.att.net/~benmlee/threads/threads.htm Conclusion from my own testing is never put antiseize on torque sensitive bolt unless the manual specify it. Use of oil is ok. Also, I think it is a horrible idea to over tighten a nut to stop a leak. Do it the right way, and machine the manifold flat first before installing.
Ben
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What the heck is this guy talking about, which permatex product, the antiseize that they sell little tubes of in auto parts stores? - can anyone say product description sheet with K factor (if you don't get what they are, do what the manual says and stay within the manufacturers guidelines). Loctite makes many grades of anitseize (so does permatex), and if you don't understand the usage of these things, I'd stay away too.
The reason for using nickel on stainless 316 (304 is a good choice too) is that if you set it up right, they do not gall nor will they - anyone who takes motors apart more than occasionally will probably use brass nuts and steel studs with anti seize or stainless nuts on stainless studs with antiseize on exhaust manifolds. If you run moly or copper or siver containing anti seize, you may well end up with huge problems (they all cook out at under 1K degrees C). A little "study" like this is good for table talk over beers with friends, but should not be taken as gospel. The guy did obviously do some homework, but he needs to qualitfy the data better.
Andrew
Benjamin Lee wrote:

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