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Exhaust bolts keep falling out...


wvumtnbkr
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So, I have a header collector right off my stock manifolds.  Th3se are 3 bolt style header collectors.

 

They keep coming loose.  We lost a bunch of time in the pits on Sunday because the one side came all the way off.

 

I am using bolts and nuts specifically for exhaust use.  I am also using nordloc washers.

 

These bolts are still loose every time I put a wrench on them.

 

Help me out here.  

 

I would like them to be able to keep their clamping strength through the heat cycles.  I am having the aluminum gaskets d3velop leaks due to the constant loosening.

 

Any help is appreciated!

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26 minutes ago, ABR-Glen said:

Can you replace the flanges with v-bands? That would be best. 

 Probably not.  They are stock cast manifolds.

 

I could attempt to weld on my spare set and see if it works.  I'd be concerned about the welds breaking.

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22 minutes ago, wvumtnbkr said:

No flex pipes.  

That’s the issue. 
Add a flexi section just downstream (maybe one foot or so) of that joint to separate the bulk of the exhaust system from the engine.

 

I had a similar thing where the exhaust manifold studs / nuts were coming out of the head. Added flex and it no longer happens.

 

Independent of my experience and solution, the issue you have is that when the engine moves or the exhaust moves it puts alternating stresses on that joint. Those alternating stresses will cause the bolts to loosen (picture a chair where you softly rock back and forth for a few hours... those legs are going to get loose... I have to tighten the bolts in my dining room chairs all the time). The only way for this not to be an issue is if both your engine and exhaust system were rigidly fixed to the chassis, and I assume they aren’t. So what you need is to separate the movement of the engine from the movement (or lack of movement) of your exhaust. 
Make sure the flex you add is high quality. We use Vibrant Turbo. When you look inside it should appear to have plate armor along the ID, not weave / mesh. 

Edited by enginerd
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18 minutes ago, enginerd said:

That’s the issue. 
Add a flexi section a foot or so downstream of these bolts to separate the bulk of the exhaust system from the engine.

 

I had a similar thing where the exhaust manifold studs / nuts were coming out of the head. Added flex and it no longer happens.

 

Independent of my experience and solution, the issue you have is that when the engine moves or the exhaust moves it puts alternating stresses on that joint. Those alternating stresses will cause the bolts to loosen (picture a chair where you softly rock back and forth for a few hours... those legs are going to get loose... I have to tighten the bolts in my dining room chairs all the time). The only way for this not to be an issue is if both your engine and exhaust system were rigidly fixed to the chassis, and I assume they aren’t. So what you need is to separate the movement of the engine from the movement (or lack of movement) of your exhaust. 
Make sure the flex you add is high quality. We use Vibrant Turbo. When you look inside it should appear to have plate armor along the ID, not weave / mesh. 

My exhaust is fairly rigidly mounted and the engine is mounted on hockey pucks.  Not *MUCH* relative movement.  Never had this issue with the other style exhaust we had on the car.  (Homemade headers versus stock manifolds).

 

Edit: not throwing this suggestion away.  Just clarifying my setup.

Edited by wvumtnbkr
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We are put together somewhat similar and the solution I have used after many failed attempts was to use long enough bolts and double nut them.

I have tried exhaust shop hardware with the nuts that have the locking finish and they too come loose.

 

Don't get me wrong, the double nut can come loose if not tightened correctly and I check them all the time. But that has worked the best of anything.

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Brass nuts.

 

I've not used them, but a friend with a mustang swears by them for this same application and reason.  He says they don't back off the way a steel nut does.  No explanation on why, but I do know loose fasteners at the exhaust flange is not a problem we've had with that car (at least while I'm present). 

 

McMaster-Carr has a good selection.

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1 hour ago, wvumtnbkr said:

No flex pipes.  

 

 

59 minutes ago, enginerd said:

That’s the issue. 
Add a flexi section just downstream (maybe one foot or so) of that joint to separate the bulk of the exhaust system from the engine.

 

I had a similar thing where the exhaust manifold studs / nuts were coming out of the head. Added flex and it no longer happens.

 

Independent of my experience and solution, the issue you have is that when the engine moves or the exhaust moves it puts alternating stresses on that joint. Those alternating stresses will cause the bolts to loosen (picture a chair where you softly rock back and forth for a few hours... those legs are going to get loose... I have to tighten the bolts in my dining room chairs all the time). The only way for this not to be an issue is if both your engine and exhaust system were rigidly fixed to the chassis, and I assume they aren’t. So what you need is to separate the movement of the engine from the movement (or lack of movement) of your exhaust. 
Make sure the flex you add is high quality. We use Vibrant Turbo. When you look inside it should appear to have plate armor along the ID, not weave / mesh. 

Everything @enginerd and others have stated is entirely correct. 

Here's a bit more info too...

Years ago my experiences as a fabricator building custom SS exhaust headers and systems for street rods and race cars taught me some lessons.

ALWAYS include flex joint(s) in EVERY exhaust system of any type.

Even if everything is rigid mounted - engine, trans, and the entire exhaust system, this is the worst thing you can do for an exhaust system!! 

No matter if the material used is 304 SS, 410 or 439 SS, or mild steel, the heat in the pipes will make them grow and shrink, the pipes are constantly changing shape and length. The system needs to have some "give" in it, and also needs to be mounted on FLEXIBLE, RUBBER hangers, similar to what you see on most OEM's nowadays.

Our rule of thumb was to always allow 3/4" of movement of the entire system to prevent stresses. This is why you see cracks in exhaust pipes, too. They were being restrained from their natural heat cycle movements, and cycled enough times against that resistance to crack them. 

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Another note: Years ago, OEM's used a type of collector on the cast manifolds that had shoulder bolts with springs on them holding the pipe flare/collector to the manifold's rounded outlet, or removable 'doughnut.' Movement is provided here.

This type of joint is still sometimes used, but it's weaknesses are some lack of movement in certain planes/angles, and susceptibility to leaks. Most often now, you see flex joints instead of the spring/flange/doughnut design. 

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2 hours ago, wvumtnbkr said:

My exhaust is fairly rigidly mounted and the engine is mounted on hockey pucks.  Not *MUCH* relative movement.  Never had this issue with the other style exhaust we had on the car.  (Homemade headers versus stock manifolds).

 

Edit: not throwing this suggestion away.  Just clarifying my setup.

Now I’m curious about your old setup and exactly how it differs from the new. 
Both are through bolted? How thick are the flanges / how long is the active length of the bolt? Does the exhaust route the same and made of same diameter tubing?

 

(aside from the above, not much movement is still a little movement and a little movement is too much. I’d bet a 6 pack that flexis will solve the problem)

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New setup bolts to cast stock manifolds.  Old setup bolted to welded homemade headers.  Same type 3 bolt connection and aluminum gaskets.

 

That's why it's a little confusing...

 

Flexis it is.  I might just go ahead and do a side exit at the same time....

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I'll probably get a lot of naysayers on this so.....salt to taste.

 

Our issue was high EGT (turbo) expansion/contraction causing the nuts on the manifold/downpipe to loosen and back off.  When I talked to our mech engineer about it, he kept telling me to just focus on keeping tension on the threads of the fasteners through those heat cycles and varying material expansion rates.   I looked at the nordlocs, but there really isn't any active pressure placed on the fastener threads.  And they're pricey.

 

I settled on stainless conical belleville locking washers and high grade steel nuts from Mcmaster.  I went belleville over the split-lock because I felt they kept a more even pressure under the nut and figured the stainless would be less susceptible to losing its form due to high heat.   This was several years ago and we've gone back to a NA, but I still use those conical washers on our manifold and downpipe fasteners.  We have not had a single exhaust fastener back off on either setup after 2 [shortened] races with the turbo and 6 or so track days with the naturally aspirated setup.

 

I could see the flex being an issue if you were cracking/breaking the exhaust in places but it seems the issue you're having is primarily fastener related.  Just my $.02.

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Get you some Nord-lock washers. An endurance car loves a good sprinkling of them here and there. Got em at both ends of my exhaust header, and in many other places too. 
 

I’d put them at both the bolt head and nut on that exhaust flange that keeps loosening. 

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I'm going to get thicker collector flanges, add 4 inch flex connectors on each downpipe and use ovalled nuts (maybe double nut).

 

If that doesn't work, Imma get out the welder....

1 minute ago, ETR said:

Get you some Nord-lock washers. An endurance car loves a good sprinkling of them here and there. Got em at both ends of my exhaust header, and in many other places too. 
 

I’d put them at both the bolt head and nut on that exhaust flange that keeps loosening. 

Have them on there....  it should say did.  Cuz they gone!

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Everyone has stolen my thunder, lots of good suggestions so far. To recap v-bands best whenever possible. Flex couplers very important for the whole system. Thick flanges very important, if they bend you lose your clamp load. high quality fasteners mandatory, you can’t use stuff from the hardware store at the header flange. Long fasteners are important, the longer the bolt the more it stretches for a given torque so the more it is able to deal with expansion and contraction. An old trick still popular in the commercial diesel world is to use thick spacers under the bolts so the bolt is much longer than would otherwise be required.

 

pkg23.png.360f56ae131148f3c86732a72d84a2a2.png

 

Stud and nut is generally better than through bolts and nuts. sounds like you have a good plan, if it was me I would get some very thick stainless flanges, at least a half inch, tap them for studs, and weld them to your flex coupler. Assuming you are using M8 try some GM 11609953 studs, they are made from A286 and have a locking thread, use those to connect the header.

 

From there weld a v-band to the flex pipe, and to both sides of the muffler, that way you have v-band connections from the flex coupler to the mid pipe, mid pipe to muffler, and muffler to out the side pipe. that should be pretty bulletproof.

 

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3 hours ago, mhr650 said:

Everyone has stolen my thunder, lots of good suggestions so far. To recap v-bands best whenever possible. Flex couplers very important for the whole system. Thick flanges very important, if they bend you lose your clamp load. high quality fasteners mandatory, you can’t use stuff from the hardware store at the header flange. Long fasteners are important, the longer the bolt the more it stretches for a given torque so the more it is able to deal with expansion and contraction. An old trick still popular in the commercial diesel world is to use thick spacers under the bolts so the bolt is much longer than would otherwise be required.

 

pkg23.png.360f56ae131148f3c86732a72d84a2a2.png

 

Stud and nut is generally better than through bolts and nuts. sounds like you have a good plan, if it was me I would get some very thick stainless flanges, at least a half inch, tap them for studs, and weld them to your flex coupler. Assuming you are using M8 try some GM 11609953 studs, they are made from A286 and have a locking thread, use those to connect the header.

 

From there weld a v-band to the flex pipe, and to both sides of the muffler, that way you have v-band connections from the flex coupler to the mid pipe, mid pipe to muffler, and muffler to out the side pipe. that should be pretty bulletproof.

 

 

As someone who works at Volvo / Mack powertrain in Hagerstown, I really love seeing you post this picture as that engine you posted won't be released until 2024-ish. Small worlds collide! 

 

I assume you work at Borg Warner. 

Edited by MichaelPal
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12 minutes ago, MichaelPal said:

 

As someone who works at Volvo / Mack powertrain in Hagerstown, I really love seeing you post this picture. Small worlds collide! 

 

I assume you work at Borg Warner. 

He did / does.  

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4 hours ago, mhr650 said:

Everyone has stolen my thunder, lots of good suggestions so far. To recap v-bands best whenever possible. Flex couplers very important for the whole system. Thick flanges very important, if they bend you lose your clamp load. high quality fasteners mandatory, you can’t use stuff from the hardware store at the header flange. Long fasteners are important, the longer the bolt the more it stretches for a given torque so the more it is able to deal with expansion and contraction. An old trick still popular in the commercial diesel world is to use thick spacers under the bolts so the bolt is much longer than would otherwise be required.

 

pkg23.png.360f56ae131148f3c86732a72d84a2a2.png

 

Stud and nut is generally better than through bolts and nuts. sounds like you have a good plan, if it was me I would get some very thick stainless flanges, at least a half inch, tap them for studs, and weld them to your flex coupler. Assuming you are using M8 try some GM 11609953 studs, they are made from A286 and have a locking thread, use those to connect the header.

 

From there weld a v-band to the flex pipe, and to both sides of the muffler, that way you have v-band connections from the flex coupler to the mid pipe, mid pipe to muffler, and muffler to out the side pipe. that should be pretty bulletproof.

 

I don't keep track of when programs will be released. I am an initial design guy, they bring me in to do the initial layout and design the first round of prototypes, maybe 2 rounds, then I move on to the next project. 

 

I move back and forth between CD and PC, just depending on what programs are hot. I can't say anything about it for a few years, but last year with remote work I designed one of the biggest programs in our history in my kitchen, nearly a billion dollars in turbos over the life of the program. 

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https://www.stage8.com/
 

https://www.wesdonautomotive.com/exhaust-flex-spring-joint-2-50-in-dia-inlet-2-50-in-outlet-6-00-in-long-wesdon-spring-flanges/?cmp_id=8102180790&adg_id=85418558602&kwd=&device=c&gclid=CjwKCAjwxuuCBhATEiwAIIIz0XIWENlbaBUQiWRtIAqGPZFrb5PlGB5XbuVP2tFHgS1CWNfJYIYLpRoChhQQAvD_BwE

 

Once we went to spring flanges after the V6 mid-pipe, we have had zero exhaust issues from 2015 on. Chain them up too as has been mentioned over and over just in case mounted break, then its less likely you will get BF for dragging pipe.

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On 3/23/2021 at 10:00 AM, wvumtnbkr said:

So, I have a header collector right off my stock manifolds.  Th3se are 3 bolt style header collectors.

 

They keep coming loose.  We lost a bunch of time in the pits on Sunday because the one side came all the way off.

 

I am using bolts and nuts specifically for exhaust use.  I am also using nordloc washers.

 

These bolts are still loose every time I put a wrench on them.

 

Help me out here.  

 

I would like them to be able to keep their clamping strength through the heat cycles.  I am having the aluminum gaskets d3velop leaks due to the constant loosening.

 

Any help is appreciated!

LOCTITE. 

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