For thost that installed the mugen header themselves, did you notice some pitting on the inside of the 4 pipes where they are welded to the aluminum plate that attaches to the engine?

I just received my header yesterday and was taking a look at it and noticed some putting inside where they are welded. Should I worry about it?

 

The Mugen header is all stainless steel so when it is welded
from the pipes to the flange the weld will get somewhat
on the inside of the tube. Mugen solution to this is to hand
grind the inside of the flange and pipe to smooth out
the exhaust gases leaving the engine. some small pitting
in the weld area is inevitable and will not effect the header
life or integrity at all. Mugen is one of the only manufactures
to do this hand clean up and it is the mark of a top
manufacture. John and i talked about this today and i, examined
4 headers from mugen to verify this. 2 of the original production
run and 2 brand new headers that arrived this week. All had
the same high quality grinding and smoothing done.
Hope this helps. Any questions please feel free to call
us at King Motorsports. 262-593-2800.
Regards
Bob Clark

 

Thanks Bob!

I have been very impressed with both Mugen quality on their parts and on King Motorsports customer service. They are a great company to work with

 

The pitting in the area noted can come from one of two things.

1) The weld bead hung on the inside of the tube did not "clean up" all the way.

2) The parent materials were not completely cleaned thereby introducing porosity into the weldment.

Most SS exhaust headers are made of 304L SS. This steel is easily formed and has outstanding corrosion resistance properties. It is a high chromium, low carbon (L) austinitic steel. It is very forgiving. In case #1 above the bead in the flow path is ground flush with the tube. Any pits are below the parent material and therefore "out of the flow". In case #2 the pores are caused by inclusions in the weld, known as weld slag. It takes a bunch to cause any damage. In the NDT (nondestructive test world) we measure the number of pores, their size, and center distances to grade, or classify, the weld. Class "A" is X-Ray Grade, "B" die penetrant, and "C" visual inspection. Unless you see a ring of large pits more then 90 degrees around your header it will last you a very, very, long time.

Utah
Formerly ASTM (American Society of Testing Materials) Level III Certified Inspector of Weldments.

P.S. My father was one of the inventors of Electron Beam Welding....the weld of all welds.

 

Utah,
Great info on how thus all works! The minor pitting
on the headers in question are in the weld area and
are very minor in scope.I think this comes about from the gauge
of the pipe (Generaly thinner than the flange it is welded to)
VS the thickness of the flange. I, think your case#2 presents
this perfectly. Very minor pitting inside a tube on the weld.
Regards
Bob@King Motorsports

 

Thanks for the informative post Utah!!

 

This is one of the best examples why I read this forum. Where else could you get such an answer for so reasonable a price? I always get my monies worth here.