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Old 07-04-2018, 11:08 AM   #2
Dave80GTSi
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Location: Central Ohio
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Quote:
Originally Posted by deathsled986 View Post
Are they different lengths because of different mounting locations on the two different style exhaust manifolds?

Or is it just that they have extra bungs for o2 sensors?

I have an 01 with some cheap ebay headers on it and the fitment of the flanges going to the secondary cats is less than desirable.

I've either got to pull them off and have them fitted and rewelded, take a gamble on another pair (probably cheaper than the customizing of the first set), or maybe switch to a cheap pair of used OEM 97-99 manifolds which will have perfect fitment but will require another set of test pipes (or bungs to be welded in?)
Both the early and the late secondary cats, as well as the early and late manifolds, are dimensionally the same (including their tubing diameters) and are interchangeable. The only difference between them are at the 3-bolt flange.

Early manifolds and secondary cat flanges have the bolt c/c distances at roughly 66 mm, as can be seen here:



While the later flanges, for some unknown reason, have these c/c distances opened up to roughly 78 mm, shown here:




I've had my fair share of aftermarket headers "not quite" fitting well, just as you seem to be going thru now.

That's why I am in the process of fitting an early non-cat manifold (cheap!) and secondary pipe system, so to replace the flow horrorshow of the OEM cat manifolds:

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Last edited by Dave80GTSi; 07-04-2018 at 11:32 AM.
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