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why use brass nuts?

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gunkholer

Member
I'm curious why there are brass nuts on the mounting studs for the risers on the exhaust system of a 454 crusader engine. The exhaust manifold is cast steel, the 9 3/8” X3'8” long stud ( 4 for each exhaust manifold ) is stainless steel that screws into it. Then the 2” thick water adapter slides on the studs and then in my case the 8” riser slides on the studs. Then the nuts are brass and they have a very thick wall to them so normally a 9/16” socket fits a 3/8” nut. In this is case a 11/16” socket is needed (The thicker wall is for strength no doubt). They also use a brass washer before the brass nuts.
My question is why not use a 3/8” SS nut and washer? The only thing I can think of, is if you have trouble loosening the nuts. Being brass, they are easier to cut off. One of mine would not budge, so a dremel with a cut off wheel, made it easy to remove it.
 
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gunkholer said:
I'm curious why there are brass nuts on the mounting studs for the risers on the exhaust system of a 454 crusader engine. The exhaust manifold is cast steel,
Most likely cast iron!

the 9 3/8” X3'8” long stud ( 4 for each exhaust manifold ) is stainless steel that screws into it. Then the 2” thick water adapter slides on the studs
I think that those would be your risers/spacers.

By the way, SS studs may be too soft and brittle for this application.
I would use grade #8 carbon steel and would protect the threaded areas with Never-Seez.
(this in one area where the Automotive Never-Seez would be safe to use)


and then in my case the 8” riser slides on the studs.
I think that these would be your exhaust Elbows.

Then the nuts are brass and they have a very thick wall to them so normally a 9/16” socket fits a 3/8” nut. In this is case a 11/16” socket is needed (The thicker wall is for strength no doubt). They also use a brass washer before the brass nuts.
My question is why not use a 3/8” SS nut and washer? The only thing I can think of, is if you have trouble loosening the nuts. Being brass, they are easier to cut off. One of mine would not budge, so a dremel with a cut off wheel, made it easy to remove it.
These nuts may be bronze. If so, Bronze will better resist corrosion.
Click to expand...
 
I received the same mix of metals when I replaced my old genuine Crusader exhaust hardware with Barr products. On a Barr riser, the stainless stud is open to the cooling seawater as it passes through the riser. On the Crusader riser, the stud was enclosed in a dry tunnel. My guess is that Barr uses brass washers and nuts because the softer brass will seat better against cast iron riser (eventually) preventing leaks.
 
Just to update and add a little more complexity by adding even another metal. I've just discovered that the washer is actually copper that goes on just before the brass nut, according to the description from one of the suppliers of the nut/washer package set.

The first couple inches of the stud is holding the cast iron water adapter in place and in it is antifreeze/coolant/fresh water. After that is the block off plate, so after that is the 8" riser that circulates salt water. But having said that, I don't see how that would have any effect or bearing on the situation. As for preventing leaks DJR, If the gaskets are doing their job no fluids should be traveling along those studs at all, right?

Once again adding one more complexity. I noticed that 2 of the studs were mild steel. Meaning that someone had replaced them at one time. The interesting thing is that those two studs were held on with SS washers and SS nuts. They loosened off fairly easily. But the studs were badly eaten up. I've had the boat 5 years. The previous owner had the boat 8 years and he had a meticulous log and there wasn't any mention about even taking apart the heat exchanger/ exhaust system. So those mild steel studs have been in there 13 years at least. I'm guessing the only reason they were used is because the 9 3/8" long studs are almost impossible to find. On a parts list drawing, those studs are identified as being SSTL. Does anyone know what the TL stands for? I think the L stands for the 316L which is a low carbon version. Which has to do with limiting heat transfer when welding. I think perhaps the T just represents Treated. I talked to a marine mechanic about just using 3/8" threaded rod, since these studs are like hens teeth to track down, and he advised against it. He said the SS studs were treated to not dissipate heat along the length of the stud and therefore the nuts would retain a consistent torgue setting. He suggested that if I used threaded rod, I might get an exhaust leak, because the nuts might loosen up from the heat. Which kinda makes sense, but doesn't explain why copper washers and brass nuts are used.

I can sort of see the principal of galling that you mentioned Diver-Dave. But those 2 SS nuts came off easy as opposed to that one brass nut I had to cut off. Plus the other brass nuts needed an extension bar on the end of the ratchet to get them free.

In the gasket package for the re-assembly, there is a pink note saying to use red locktite on the threads that go into the exhaust manifold but not to use never-seize on the other end, as it acts like a lubricate and will cause the washers/nuts to loosen.
 
gunkholer said:
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The first couple inches of the stud is holding the cast iron water adapter in place and in it is antifreeze/coolant/fresh water. After that is the block off plate, so after that is the 8" riser that circulates salt water. But having said that, I don't see how that would have any effect or bearing on the situation. As for preventing leaks DJR, If the gaskets are doing their job no fluids should be traveling along those studs at all, right?
...
Click to expand...

Yours may be different, but on my Barr replacement risers, the stainless studs are exposed to the seawater. The washer and nut hold back the water. I ended up using a dab of silicone on the washers and nuts when I torqued them.
 
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gunkholer said:
Just to update and add a little more complexity by adding even another metal. I've just discovered that the washer is actually copper that goes on just before the brass nut, according to the description from one of the suppliers of the nut/washer package set.
The copper washers may be there to account for different rates of expansion re; the SS studs and the Bronze nuts.

The first couple inches of the stud is holding the cast iron water adapter in place and in it is antifreeze/coolant/fresh water. After that is the block off plate, so after that is the 8" riser that circulates salt water.
What are you calling a "cast iron water adapter" and a "8" riser"?
(see images below)

But having said that, I don't see how that would have any effect or bearing on the situation. As for preventing leaks DJR, If the gaskets are doing their job no fluids should be traveling along those studs at all, right?
I would agree!
Click to expand...


These are examples only.
 

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DJR said:
I received the same mix of metals when I replaced my old genuine Crusader exhaust hardware with Barr products. On a Barr riser, the stainless stud is open to the cooling seawater as it passes through the riser. On the Crusader riser, the stud was enclosed in a dry tunnel. My guess is that Barr uses brass washers and nuts because the softer brass will seat better against cast iron riser (eventually) preventing leaks.
Click to expand...

I've just discovered what you wrote about the SS stud being exposed. I'm reconditioning the exhaust/heat exchanger system on my stbd engine at the moment. But recently I took all the components of my port Engine in to be boiled out and the 8" elbows didn't survive, so the company doing the boiling ordered me a pair of new 8" elbows. On those elbows as I mentioned, the casting around the holes that the studs slide through are solid one end to the other. However,,,, last night I started to clean out all the crud and corrosion on the stbd. engine 8" risers and low and behold they are the ones that you have DJR. If I hadn't read your post first, I would have thought my burr and die grinder had broken through the casting wall and I would have been heart broken. haha. So thanks for sort of warning me.
But it seems crazy to design the riser this way. ??? I'm assuming you're happy with the silicone you used? Did you smear it all around covering the entire back side of the flat washer? Or just a tiny bit between the stud and casting? Did you use any particular type of silicone? Such as high heat type. How long ago did you do this. ( engine hours) ?
I'm going to take my heat exchanger and trans. cooler in to be boiled out since I can't get inside them to clean them out, so when I do I'll ask the company where they got my new 8" risers from.
 
I replaced my hardware in the spring of 2016, and it has about 200 hours on it now. I see evidence where one stud has a slow drip. As far as sealing it goes, I first removed the paint on the risers' landings for the copper washers. Then I applied a thin layer silicone at the washer to riser, at the nut to washer, and on the stud threads where the nut ends up. I probably used Ultra Black silicone, but I don't think matters, since the riser doesn't get very hot.
 
I've just noticed a small chamfer around the hole on the casting. I'm wondering if a 3/8" o-ring might be a good idea? The problem would be getting a smooth surface on the old casting. Perhaps one of those round pink stone dremel attachments would make a clean uniform seat for the o-ring.
 
those chamfers are just for stress relief.....

as far as using O-rings....the primary seal is intended to be the gaskets.....you'd be adding another seal that may interfere with the interface used by the primary.....if you desire to seal the studs, just use PST or a low strength version of Locktite....
 
makomark said:
those chamfers are just for stress relief.....

as far as using O-rings....the primary seal is intended to be the gaskets.....you'd be adding another seal that may interfere with the interface used by the primary.....if you desire to seal the studs, just use PST or a low strength version of Locktite....
Click to expand...

There is no gasket at this point. The opening in the casting for the stud to slip through is slightly larger than 3/8” (obviously). At the point on the stud where the copper washer seats against the casting there are threads which allows even more room for fluid to escape. It's a really dumb design. I suppose I could make a gasket the shape of a washer with a really tight opening on the inside of the gasket around the threads, and then use Permatex aviation form a gasket #3 sealant on the back side of the custom gasket before the copper washer.

 
I recall when I had the outlet adapters. From memory, the studs were wet in use, and the copper washer was used for sealing on both sides, and the self lock nuts sealed against spiral leaks at the threads. All told, somewhat a marginal design, and I ultimately put on the later rev manifolds, and not needed the adapters (so-called donuts).
 
gunkholer said:
What's a rev manifold diver_dave?
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Crusader designed a new exhaust manifold (actually two, L and R), that have the water return hose outlet cast in. It means no more donut water adapters.

Overall, it will be an inch or two shorter than existing, but I did the replacement, no issues.

Example: Old right side exh manifold part no = 97114; new manifold = 97992. The FWC adapter (97295) then is not needed.
 
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