The already beaten to death stud/bolt question...
 

So, I know this has been hashed over in a very hard long thread over 40 pages long, and i don't want to crap on anyone's other ideas, but I was wondering how many people would drill/tap for Standard Hardware over Metric? How many are already tapped for Metric, say, 10mm hardware and wouldn't be comfortable re-drilling/tapping for slightly larger standard stuff? I'm running an FMII manifold, going to be running a setup that seems to be the brainchild of a fellow going by KVerges on the forums, at SpecMiata. He used this on his Turbo sm cars.

This is the hardware in A-286. Should be fine for my application since I'm going for <20lbs, Marginal HP goal, and I will not track my car terribly hard/often because there just isn't enough up here, but these bolts will solve the issue once drilled for lock-wire. The point is, and I am sorry I suck at getting to the point, but it is that you can get off-the-shelf Standard hardware in the states easily for 1/2 to 1/4 the cost of what it will take anyone to get this stuff machined in Metric from bar stock. There is no way in hell there will be enough Miata customers to buy 10,000bolts or more, where you could get the cost down. So, I was just curious if it is worth it for me to pursue this any further than getting maybe 10-12 sets and never doing it again for myself and a few acquaintances.

Basically, drill/tap the manifold-turbine flange on the manifold side for 3/8in and STD. fine threads. Notch the side closest the driver for use of bolts, that is, take the material out so it can slide on to the bolts. Install the 5/16 bolts into the turbine-downpipe/outlet whatever you have. All bolts could be drilled by me for lock-wire, similar to a pic attached, but for all 9 bolts, so no Nordlocks.
Attachment 201897
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A286 = good, but studs > bolts. Anytime.

Usually true, but in this case I think the bolts will be far superior to any studs anyone uses at this time. They maintain a high degree of strength at temperatures that are the ruin of your typical stainless steel.
In this case, should bolts work out, they give you a degree of simplicity too, taking out unnecessary components.

I do understand if anyone isn't willing to take my word for it though. I honestly need to have this running and tested personally, not just base it on someone else running the exact same setup for the last few years in a number of cars, I suppose.

It's not a material issue, it's a design issue regarding torque.

You can have a superior material bolt, but have it fail sooner due to inconsistent torque loading. With a bolt you have two torque values, one for the "tap end" of the stud which goes into the flange (usually a relatively lower value), and another for the flange pressure needed with the nut.

This is superior in design due to the two different loading applications being torqued to suitable value. With a bolt you are torquing both at the same time, making it nigh on impossible to have proper thread friction and flange pressure at the same time.

I may have forgotten a few things from that part of mechanical design, but I hope not since my final is in an hour (EDIT: EEK! 45 min).

Pretty close to got it I'll agree. Necked down bolts typically solve this issue, but are a one-time deal for use, so I won't be going that direction. I'd also argue this is more of a materials issue, because no matter how surperior in design your stainless steel stud/nuts may be, they loose large percentages of their strength at high temperatures. This is one reason they stretch. They are holding two pieces together, at least one, if not both cast iron, and the expansion at 1600+ temperatures pulls on the stud enough to permanently deform it, because at that temp the stud/nut have a lot less strength than when you put them on at room temp.

I just took off 9 studs/nuts from my manifold today, and 4 of them had the nut bound to the stud quite firmly, effectively making it a bolt for the rest of its life. Though, when applied originally they had better torque properties, sure.

Anyway, Its fine, i'm going to stick with my bolt/286 setup for now, and I hope it works out well for me. I've got one guy who has ran it already, so I'm going on his advice.