truck turbo manifolds ???
01-24-2014, 08:17 AM
#21
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You make a good point about the value of studs ls1_chevelle, and I can appreciate your sense of humor. I would caution against using stainless steel studs and stainless steel nuts. If ARP only offers SS studs I hope they supply them with a dissimilar metal nut? Stainless-on-stainless is just a bad combination for galling.
Slightly contradictory but you are correct that over stressed bolt failure isn't a common problem on exhaust manifolds. No doubt stainless studs have enough strength to work, I was just pointing out that they aren't stronger than carbon steel.
Slightly contradictory but you are correct that over stressed bolt failure isn't a common problem on exhaust manifolds. No doubt stainless studs have enough strength to work, I was just pointing out that they aren't stronger than carbon steel.
I'm very familiar with SS on SS gulling. The nuts do appear stainless, Ive had them on my car for 2 years now and have had my manifolds off several times. I was waiting for the galling to happen but there is zero signs of it. I want to say they are a different material because of it.
I agree with you, theres a reason ARP uses carbon steel(general term not being specific) for their head studs/rod bolts/main caps/ etc and heat treats them.
01-24-2014, 12:20 PM
#22
9 Second Club
You make a good point about the value of studs ls1_chevelle, and I can appreciate your sense of humor. I would caution against using stainless steel studs and stainless steel nuts. If ARP only offers SS studs I hope they supply them with a dissimilar metal nut? Stainless-on-stainless is just a bad combination for galling.
Slightly contradictory but you are correct that over stressed bolt failure isn't a common problem on exhaust manifolds. No doubt stainless studs have enough strength to work, I was just pointing out that they aren't stronger than carbon steel.
Slightly contradictory but you are correct that over stressed bolt failure isn't a common problem on exhaust manifolds. No doubt stainless studs have enough strength to work, I was just pointing out that they aren't stronger than carbon steel.
There is nothing contradictory. A stud by nature is always stronger as it places less stress on the aluminium threads in the head.
I do agree that stainless can gall, and it's very annoying when it does. But when the "studs" are just screwed in finger tight, it really doesnt matter. If it does gall up, just screw the stud out and replace it.
Ive had mine like this for a few years, it's been apart many times and Ive never had a problem.
Ive had more galling issues on much larger stainless fasteners though. Almost never on smaller ones.
But again, studs are just far easier to work with. One example....I currently have a manifold with turbocharger attached. From under the car I can lift this into place, slide it over the studs. It will hang there til I go up top and put a nut on and tighten it into place.
With bolts, that same task either requires two people, or would be a complete and utter bastard to do.
Really, it's a no brainer to opt for studs here, regardless of what material they are made from. It's not like they cost money to DIY some.
Even some cheap M8 threaded bar could easily be cut up and used.
01-24-2014, 04:15 PM
#23
The carbon steel used in the automotive industry (eg, engines) usually contains 0.40-0.50% carbon -- a medium plain carbon steel that is then hardened. Although it has a higher yield strength, it's more brittle than stainless steel. They use carbon steel for exhaust manifolds because it's cheap. It also corrodes quickly, which is why the bolt heads often break off when removing them.
Galling shouldn't be an issue with SS at the exhaust area, as the block & manifolds are dissimilar metals. If you're really that worried about galling, use anti-seize and don't crank the **** out of the bolts -- torque them down. Actually, galling of SS should be less of an issue than corrosion in carbon steel bolts in that area.
01-24-2014, 05:01 PM
#24
How does the dissimilar engine block and exhaust manifold material affect galling between a stud and nut. Maybe you are confusing that with galvanic corrosion? Galling in this context is metal transfer between threads of a stud and a nut.
As stevieturbo aptly pointed out, with galling on a stud you can simply back it out of the head, throw it away, and use a new one. It seems however that ARP is using dissimilar metals for the stainless studs and the nuts so they have avoided galling and provided a stud that doesn't corrode. And since the exhaust manifolds with 6 studs don't over stress the bolted connections the use of stainless steel isn't a factor - even with it's reduced yield strength at elevated temperatures.
If you want to continue that conversation just look up the yield strength for carbon steel vs stainless and note how much quicker stainless yield strength reduces as temperature increases. Granted, yield strength is not a concern in this application of an exhaust manifold stud - it simply started out as an exchange of information that stainless is not stronger than carbon steel.
As stevieturbo aptly pointed out, with galling on a stud you can simply back it out of the head, throw it away, and use a new one. It seems however that ARP is using dissimilar metals for the stainless studs and the nuts so they have avoided galling and provided a stud that doesn't corrode. And since the exhaust manifolds with 6 studs don't over stress the bolted connections the use of stainless steel isn't a factor - even with it's reduced yield strength at elevated temperatures.
If you want to continue that conversation just look up the yield strength for carbon steel vs stainless and note how much quicker stainless yield strength reduces as temperature increases. Granted, yield strength is not a concern in this application of an exhaust manifold stud - it simply started out as an exchange of information that stainless is not stronger than carbon steel.
01-25-2014, 02:03 PM
#26
Just my two cents, but the stock bolts are galvanized. this is a good thing, when threading into aluminum. Stainless is a very bad idea, threading into aluminum. It will pull the threads right out, before you even think it's galled up. And, stainless is weaker than a gr. 10.9 stock bolt. Also, when threads are cut, for using galvanized bolts, they are cut deeper, to allow clearance for the zinc on the bolts.
01-26-2014, 03:47 AM
#27
9 Second Club
If you tighten bolts so much you pull the alu threads, you deserve the damage. Of course its another good reason to use studs regardless of what steel they are made from.
