I'm finishing up an exhuast system but I have some questions regarding the hardware. I have a new 4-2-1 header w/ a 2.5" collector that utilizes a donut gasket. The header has a flange welded onto it before the collector, and I finally sourced a flange that mates up to it of the correct size. However, I'm wondering if the flange that mounts on the <U>exhaust pipe side </U> should have an "oval cutout" for the bolt holes so that the exhaust can pivot freely from left to right. Hopefully the pics will help out a bit:

General Example of a Donut Gasket Setup (click link for pic):
http://www.randomtechnology.com/GPInstallation.htm

My exhaust side flange, the bolt holes are of one size (not oval) and don't allow movement of the bolts:



Or should I be using an exhaust side flange such as this (oval bolt holes):
http://www.roadraceengineering...h.jpg


*** Unfortunately my header flange has bolt holes that are 4.75" across from each other which doesn't seem to be a common sized flange, so I lucked out on finding the exhaust side flange. I just need to know if the bolt holes on the exhaust side flange should be opened up to allow the complete exhaust to pivot under load. Guess I'm used to flex pipes... TIA

 

???