I like rolled threads better. Cut outside threads are hard to make without stress risers.

 

was just about to say the same thing. cut threads bad. rolled threads good. just make sure the root of the threads has the max radius allowed by ISO...

 

Well jeeze guys sorry I don't a million dollar thread roller.

 

I'll go in for $5. Now we just need 199,999 more contributors. Plus I get some free bolts.

 

Alright guys, so I've got some fasteners here and the material was a little harder then expected to find. I've had machine shops all over the US trying to track it down. The good news... I found it! Its in Malaysia evidently.

So the price of the kit with the studs, lock washers, and nuts would be about 80-85 dollars shipped for the 9 studs in question. The average cost is about 6.75 per stud. (this is before I am absolutely sure of the shipping cost from Malaysia, I just estimated. If they have to put it on a row boat and get it here there maybe goats, cows, or talismans involved in the shipping cost as well.)

Now onto a another issue all together. The manufacturers that use stainless as a header manifold: That is about the most ridiculous thing in the entire world to do. I didn't realize why it was so bad until I actually got to talk to a metallurgist about this, and done a bunch of research.

1.) Stainless steel is already close to the lowest of all steels when it comes to strength. Doesn't matter the grade.
2.) Stainless steels are just about the most incompatible with both aluminum, and iron as you can get when it comes to thermal expansion.
3.) Stainless steels have no high heat strength properties. It mise well be butter when you warm it up.

So if you want a trick manifold use some high alloy nickel content steel or inconel to do it with. Then at least you could use normal fasteners because those kinds of steels are thermally compatible with standard fastener materials.

Back to business. Does anyone want to work with these fasteners? I understand they are expensive but unfortunately the only grade of stainless that anyone would consider strong at high temperature isn't cheap. What do you guys think about this?

 

I forgot to mention... did another 2 day event. Still all tight.

I really think the issue is the people with vertical flanges. You have all that weight stretching the top studs. Brace the turbo.....

 

I thought the studs were only a problem on the turbine to exhaust manifold side because the iron turbine flange expands so much. It wasn't as much a problem on the downpipe side because the flanges were both a thinner thickness and typically fabricated steel, not iron. B i wrongz?

 

4) mild steel is cheaper anyway.

 

I'd be in for trying just 4, M10x1.5 manifold to turbine studs, washers, and nuts assuming the price changes at the same (or better) ratio then the number we need. If that works I would consider a set for the downpipe if that ever becomes a problem.

 

Stainless gets the job done quite well for corrosion resistance.

High nickel iron means a casting, which excludes it from my manifold project. Anyway, a lot of the OEs are going away from Niresist and other similar formulations to austenitic stainless steel due to lower cost and improved performance.

High nickel alloy materials are insanely expensive. And I don't mean just kinda insane.

The right grade of stainless, properly fabricated and braced, seems to be the best option for, oh, just about everybody.

 

+ 1

 

Yea, but if it was made from mild steel which is half the cost of stainless, no one would have fastener pull out problems. PERIOD

I said if you wanted to go to a trick manifold use a high nickel content steel. If you just want a standard manifold mild steel works fine. I talked to a metallurgist who is far in advance of my capacity for material science. He graduated in the 70's and is the master metallurgist for EMJ steel. I'm just going with my gut here that he knows what he's talking about.

 

While in theory everything you've said makes sense, for our application, stainless works fine and looks 100x better doing it. Your metallurgist is not wrong it just doesn't apply to our manifolds. Think of our aluminum pistons. aluminum has a melting point of 1200F and a higher expansion rate than steel. Doesn't sound ideal for the hottest part of the engine but the benefits outweigh this. More importantly it works.

Stailess is/has been used for exhaust manifolds for years without problems. I would try a ss runner manifold with mild flanges before going to a full mild steel manifold if the different expansion rates are an issue, although the problem really seems isolated to casted manifolds.

 

I'm not getting into a war here on this. I know alot of people spent alot of money on their setups. I just think it was a poor design choice. You could make a stainless heat shield over the pipes if you didn't like the looks ya know? These pull out problems are mostly to do with the people who are running the limit, and at the limit, stainless causes problems.

 

Full-Race, AMS, TiAL, and several other extremely high-end race shops disagree with you and your metallurgist. When can you get the stainless studs to market?

 

Bread crumb:

So I'm not happy I only have one source of the steel I'm going with.Therefore I'm going to do even more research and see if I can find something that is atleast local, and maybe better.

The stainless I was looking into was 316Ti, a titanium stabilized grade of 316. It is an ok material. I highly doubt 316 by itself will work, but its an upgrade from 304.

 

Travis - what do you think of this:
METRIC CLASS 8.8 STEEL SELF-LOCKING STUD, M10, 52MM OVERALL LENGTH, 1.5MM PITCH, PLAIN STEEL
I guess 'general purpose steel' doesn't tell you much. But I will say after getting harder and harder studs these worked.

Can you remind me what your setup is again? This thread's so long I gave up after skimming 20 pages.

That was my same thought: The issues are with the 4 main studs. The cost is not at all unreasonable. It sounds like a lot for a bolt, but I'll take one bolt that works over a bag full of ones I have to replace every 3 weeks.

Certainly most of the tubular manis I've seen seem to die when abused, and stainless much much worse than mild. One of my fab friends just won't do stainless anymore - he loves it for some things, but for manifolds it's mild all the way.

How often do those end up in for repairs? Its unwise to ignore what everyone is doing, but it IS possible for everyone to be wrong. Or to have different goals. I've worked at many a company where marketing and "public image" and "market desires" have take a product that worked well and turned it into a piece of crap that everyone wanted. I'd say if their stuff WORKS it's worth looking at their design. If they all have a common failure mode, that's worth looking at as well. I can't comment on those, but all the weld shops/friends I talk to around here spend most of their time repairing SS manifolds.

Then again, my cast one keeps cracking. :-)

 

Surely those sorts of makers are using the highest quality stuff you can get (screw the cost) and as cars are serviced after every event (if the owner is sensible). Isn't this then a moot point as we are not race teams?
Just a thought I realise some will be funky enough for the cool kit.

 

And the higher end shops use Inconel... can FR, AMS, and TiAL show their research and prove that one is better or do people just spend more money on shiny polished stainless?

When I got my manifold a brazilian years ago, I picked mild steel for two reasons: First, people I trusted suggested it would have better thermal cycling behavior compared to SS and Second, it was cheaper. I didn't give a rats *** if it was shiny.

 

Travis,
The problem is with the expansion of the cast iron side of the connection, the turbine housing mounting flange. When using studs it doesn't matter if they are in an iron, stainless, mild, chrome moly, or titanium manifold because if the manifold expands and contracts, the studs aren't being stretched. The expansion that effects studs is in the turbine flange.
This, of course, only applies to studs and not to bolts. Bolts have the expansion of both the thickness of the turbine flange AND the thickness of the manifold flange to compensate for.