426 cyl head to header joint

[eunos]

I was checking the fit of the header pipe into the exhaust port on our 01 426 today and was "somewhat surprised" at the variations in diameters, so I checked them and came up with the following:
port diameter 36.5 mm
copper seal dia 35.5 mm
header at seal joint 38.5 mm
weld seam in header 37.5 mm
All these sizes occur in a length of 12 mm from the edge of the port! I thought the essence of good exhaust design was to have a smooth a transition as possible especially at the head joint.
Anyone got any thoughts or fixes?
thanks, Kevin

 

[SFO]

This is an interesting observation.
I have been taught that the most critical part of an ex. pipes design is at the high velocity area of the first 12".
I have seen more than one tuner try to grind the anti-reversion hump out of the yz-f ex port.
WB sells a torque stuffer that plugs the ex port by restricting the dia. at this junction.
Modifying the flow of the exhaust gas at this union will certainly change things.
If you get what you are looking for is only a function of what you want

 

[eunos]

Thanks SFO, do you know if the first section of the header (the part that`s machined and welded to the pipe) is titanium or steel? If its steel I`ve got a fix in mind that could smooth the whole lot out.
Thanks,
Kevin.

 

[eunos]

Thanks SFO, do you know if the first section of the header (the part that`s machined and welded to the pipe) is titanium or steel? If its steel I`ve got a fix in mind that could smooth the whole lot out without restricting the diameter.
Thanks,
Kevin.