Quote:
Originally Posted by Calum
Were the flanges damaged due to persistent leaking? Warped to due over tightening? Something else?
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At least one I know the inside nut on one side wasn't fully tightened, as it is in a tight space and really needs a crow's foot to best torque it down. This caused a leak that blew out the gasket and did cause the flange to warp. Another one sitting at my office, the bracket was not fitted down to the block at the turbo end and was sitting on top of the nut head, pushing it out and causing the header to crack at the flange over time.
One of the more common ones, that happened in a couple of cases, was lack of exposure to a split header design (which is relatively unique to the boxer engine). They decided that the right and left flanges were not flat in relation to the other, and put the flanges on a flat grinder. This caused them both to no longer be square. The most extreme example, they took 10mm out of the flange. Of course, if they had just bolted it down properly they would have noticed the header flexes enough to bring it square.
There were a couple of cases where the flange surface was not fully flat, and that is our fault. They probably had warped during the welding process. But this is out of 270 kits sold worldwide, so it's not exactly a common occurance.
Edit: Here is an illustration I made a while ago to explain what was happening.
The first illustration is of a manifold bolted down, the second of the manifold before it has been bolted down. There may be a slight bend in it from side to side, this is common with solid pipes as the heat cycle. The third illustration shows what happens when somebody tries to grind them flat in relation to each other.
