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Hi all, replaced the cat section today. The bolts (with what look like valve springs) that secure the pipe to the headers - how tight should they be? One side seems to be almost totally wound up, the other with less tension on the spring.

Any thoughts?

Cheers - Mike

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With the mid-pipe (and muffler) properly positioned and aligned with the exhaust manifold, the two spring-bolts should be near symmetric, with equal compression of the two springs (normally you tighten each bolt until the unthreaded portion of the bolt reaches the nut, otherwise the nuts would be loose). It sounds like you may need to loosen the clamp between the mid-pipe and muffler and shift them around a bit to better align the mid-pipe with the exhaust manifold.

As I'm sure you know, that junction is designed to allow some motion between the exhaust manifold (and engine) and the mid-pipe (and muffler). Motion is needed because both the engine (due to torque and vibration, as allowed by the motor mounts) and the exhaust (due to cornering g's, bumps etc, as allowed by the rubber exhaust hangers) can move. When you fit the mid-pipe and muffler to the exhaust manifold you want that junction to be near the center of it's range-of-motion to allow as much motion as possible.

HTH, -Ed
 

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2008 Exige S240
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Be sure to use all metal lock nuts.
One time I did not and one of the spring
loaded header to cat-pipe bolts fell out
causing a horrible exhaust leak.
(these are not nylocks)
 
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