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Old 01-20-2013, 10:24 PM   #1 (permalink)
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Post Bolts ?

Hi all,

During my 73 disassembly I remove a fair amount of nasty nuts and bolts. I was very lucky in that I had to cut off only 1 bolt to date. Even the exhaust manifold bolts came out intact. I am contemplating replacing bolts and nuts. Does anyone have any thoughts about using stainless steel to replace much of this nasty stuff ? I put stainless steel in my manifold to downpipes 15 years ago, and once broken loose, they unscrewed by hand. I'm curious what the intent of MB using studs and nuts in most places on those manifolds and bolts in other places. Obviously studs are nice when installing gaskets. I would like any thoughts regarding substitutions. Even if I leave the stud/nut configuration, I'd like to use stainless. Seems like all fasteners in a car should be stainless. Other than the cost is there any dissimilar metal corrosion issues ? I need to go thru each ziplock parts bag and either refurbish or replace. Thoughts ?
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Old 01-20-2013, 11:04 PM   #2 (permalink)
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Most garden-variety stainless steel nuts/bolts you see in the stores are not as strong as conventional steel IMO. No doubt, exotic (expensive) bolts are as strong or stronger. Obviously, using something less strong would not be acceptable, period.

Galling is a problem with stainless steel threads (especially on aluminum!), but this can be beaten by using a coating on the threads. How compatible this is with thread-locking materials, I don't know.

I think that the bolts from MB are pretty good. It would be nice to have them replated with cadmium like they (and most of the other steel parts) were when they were new. Very few companies will do this now because cadmium is very toxic and regulated. A modern replacement exists (zinc chromate?) but it doesn't look exactly the same and may not last as long. The good news is that this is done with "barrel plating" and it is fairly inexpensive. The bad news is that some of the parts you would like to do can't be done because they have to be immersed (fuel pressure dampers, for example).

On parts where this is practical, I've painted them with thin layers of weld-through primer (expensive, very high zinc, silvery), outdoor gold, and them high-temp engine clear with results that have looked good after several years of year-round driving. This won't win a concours but I am satisfied.

Homebrew MB First Gear Start!

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Old 01-20-2013, 11:21 PM   #3 (permalink)
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This is just the type of information I'm looking for. I think ill take your suggestion and look around Portland Or. For a cad plater. That would cover 80 percent of the bolts. Perhaps I can get the exhaust boltset from MB. The problem with replacing is Thete are a million sizes and types in this beast ! Keep the good info coming. Thanks !
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Old 01-21-2013, 03:16 AM   #4 (permalink)
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I too have been told S/less is not as strong and they are very expensive vs normal steel.I think maybe good quality black treated with anti seize is fine for most applications.
Rusty bolts do give me the ***ts though.I won't ever put one back.I just replace them as I come across them.I have a bunch of 6,8 and 10 mm in various lengths handy.Allens I just buy as needed.
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Old 01-21-2013, 07:22 AM   #5 (permalink)
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For rusty nuts and bolts you may want to give this a try...

Metal Rescue - Home

Wire brush the loose stuff and then does work.
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Old 01-21-2013, 08:48 AM   #6 (permalink)
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I've been doing some research based on you guys opinions. As you say, the stainless seems to be problematic as far as galling and strength. A couple of the hot rod builders sites have some pretty good information regarding fasteners. ARP has a wealth of information as well as strength etc. They have complete bolt kits for most domestic as well as some import. Just not Mercedes ! It seems that in some cases just plain tensel strength is not adequate. A lesser strength bolt is required to provide some stretch and therefore clamping action. If the strongest bolt possible is used, they break instead of flexing. It can't ever be easy !
Most of my engine bolts will probably be reusable, perhaps with a cadium refurbishment. I am not taking head bolts out at this juncture. Even so, internal fasteners are usually in great shape unless they are specified as single use applications.
I think I will check EPC and see if I can get the exhaust set and go with manufacturers. My suspension fasteners were in great shape so will be ok as well. Perhaps the worst were anything in the floor pan. These are going to get a stainless replacement as they live under the car. Many of the fasteners inside the car that hold trim need a replacement just due to loss, and general abuse or rust. Especially cosmetic fasteners. So the quest continues. All comments are appreciated and I will use the collective knowledge to try to pull this thing together. Thanks as usual !
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Old 01-21-2013, 09:57 AM   #7 (permalink)
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Best source I've found for comparing and buying fasteners. Minimum quantitys apply but a bag of 5 is usually cheaper than one from Benz.
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