Exhaust manifold studs??

[_JohnnyD_]

While I was mocking up the exhaust manifold for customization/lengthening I realized that I had to lift the motor 15cm every time I removed and installed the manifolds because the distance between the end of the exhaust manifold studs and the frame was not large enough to remove the manifold.
Today I removed all of the old studs (engine is now out of the car) with the intention of replacing them with new studs and I started thinking.

Why do I have to use studs, why can't I just use bolts?
On the one hand I can't think of an engine that uses bolts for the exhaust manifold, one the other had assuming the correct grade of bolt is used there is no mechanical or physical reason not to use them.

Please let me know if I'm missing something here?

[JGood]

I think the reason for studs is because getting the manifold and gaskets installed with bolts would be a PITA... Sort of like using BMW's wheel bolts and spacers, it's a hassle compared to studs.

I guess you'd just have to go with whatever you'd rather deal with. But I'm able to remove my manifolds in the car with room to spare...

[FunfGan]

Its not too difficult if you do use bolts. Thats the same way my 5.0 headers go on, just put 2 bolts at opposite ends and get those started.

[nando]

I think the reason for studs is because getting the manifold and gaskets installed with bolts would be a PITA... Sort of like using BMW's wheel bolts and spacers, it's a hassle compared to studs.

I guess you'd just have to go with whatever you'd rather deal with. But I'm able to remove my manifolds in the car with room to spare...

no, it's because they are threaded into an aluminum head.

if you use bolts you're more likely to strip the threads in the head. actually, I'd say it's more a matter of if, not when, you'll strip the threads in the head when using bolts.

studs are clearly superior to bolts in almost every application, the only disadvantage they can have is convenience.

also, BMW uses copper locknuts on the exhaust manifold studs. if you use regular bolts, they will certainly come loose.

[JGood]

Oh, I see. What about all of the other bolts that thread into the aluminum head... Like the timing cover bolts? And the oil pan bolts in the aluminum block?

[nando]

oil pan bolts come loose all the time, but there's usually a *lot* of them.

timing cover bolts may just be a convenience/fit thing. if they could use a stud instead, they would, but it would be difficult/impossible to get the cover on.

also, none of those bolts have to deal with anywhere near the temperature/expansion changes that the exhaust manifolds go through.

[JGood]

Gotcha. Good to know!

[ForcedFirebird]

also, none of those bolts have to deal with anywhere near the temperature/expansion changes that the exhaust manifolds go through.

It's all about heat cycles. Easiest way to remove a stubborn thread is heat, so the cycles and dis-similar materials is what causes them to come loose.

Sine the studs no longer work on the headers we manufacture, we sell Percy's locking header bolts, they work great!

[_JohnnyD_]

I agree, my biggest concern was the bolts coming loose. I spoke to a few people and even though there are a few thread locking products that advertise being capable in high heat, I don't trust them. The locking bolts are a good idea but they are expensive. I think I'm just going to try slightly shorter studs.

[ForcedFirebird]

Percy bolts aren't that bad. $52 for 16 of them.