Re: Choice of materials for exhaust manifold.
 

Anyone who is buying a log manifold obviously doesnt care much for flow and is looking to save money, so yeah I would just use mild steel.

I actually find it easier to weld stainless because of how the heat stays very centralized. With some good prep work and a back purge, you will never get any sugaring on the inside of the tubing. If you dont prep your material the exact same thing will happen with mild steel.

Read my previous post. DONT USE STAINLESS STEEL FLANGES. Even if you do use stainless steel flanges, think about it. A lot of nuts and bolts nowadays are stainless steel. Therefore, they will expand with the flange.

The log can go through 8234237 heat cycles and nothing will happen to it as long as all of the welds penetrated all the way. Explain to me what would cause the log to fail if all the welds have fully penetrated. Do you think that mild steel doesnt expand? Mild steel expands a shitload too, just not as much as stainless steel.

Re: Choice of materials for exhaust manifold.
 

The log is expanding at a different rate than the head which leads to movement at the head be it either lov vs flange or log vs head.If you dont cut between the runners the manifold will turn into a bananna,if you do it will constantly loosen the bolts at the head.There is no way around this.

Re: Choice of materials for exhaust manifold.
 

Yeah but the head is aluminum, so how does mild steel help?

Re: Choice of materials for exhaust manifold.
 

The head is liquid cooled ;)

Re: Choice of materials for exhaust manifold.
 

Don't the outer ends of the manifold compress harder against the head when the manifold is heated up? I think I recall this is why the old V8's exhaust manifolds get lesser torque settings on the hardware in these areas than the hardware in the center of the manifold.

Is this the "bannana effect" is wich you're referring to?

Re: Choice of materials for exhaust manifold.
 

Still not buying it.
I can heat aluminum by pissing on it.

Re: Choice of materials for exhaust manifold.
 

im not questioning what you "know" i am just telling you my real world experiences.

people have been running manifolds for a long time, and ive never heard of or seen a problem. i know guys with flux core miggedlogs that have been going hard for years.

stainless all the way for me.

the price difference doest warrent the use of mild steel ever.

i have used quite a few stainless head flanges as well, also with no problem.

Re: Choice of materials for exhaust manifold.
 

All of what Slappy says makes sense. The fact of the matter is I have seen and built quite a few manifolds and some have been in heavy use for years with no problems. I guess if you intend on running really lean and high exhaust temp for 10 years then you may have an issue. Honestly how long do most guys run a manifold for?

Re: Choice of materials for exhaust manifold.
 

2 weeks

Re: Choice of materials for exhaust manifold.
 

Till his nuts drop ;D j/k.

Alot of the 1.9t VW guys(elitist pricks :P) have alot of problems because they run high boost and extremely high EGTs.