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Discussion Starter #1
I bought a 2.5" test pipe on ebay. I'm trying to figure whether these bolt center measurements are right, and if so, where to find a flange large enough to match. The plan is to weld another flange on the downpipe (turbo), which currently has a 2" flange/pipe welded into a 2.5" pipe. It's the only bottleneck I can find (other than the previous test pipe) in my entire exhaust. The flange bolt center looks to be about 4.75", which doesn't appear to be common at all; can't find them on the net. Am I measuring this right? I get the feeling like I'm missing something obvious.

 

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Discussion Starter #3
Okay, before I get ahead of myself trying to make two different flanges meet, the downpipe flange is the issue. The 2" is welded within the 2.5" pipe. I thought it would be best to cut it off at that point and weld on a new flange--which is why I'm trying to match the test pipe flange bolt center (4.75"). What is the right way to fix this?

 

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ej8
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6,365 Posts
Your still need a donut gasket.
Your going to have to get one that will fit inside the curve of the car.
Then the ID would have to match the pipe your using.

Right now you have a 2inch ID and 2.5 OD for the donut gasket.
find out what side the cat OD of the curve is and go from there.
You very well could just get a 2.5 inch 2 bolt flange.
 

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Discussion Starter #5
Yes, that I understand. I have both the old and new:



The larger donut is for the test pipe (came with it). The problem is how to match the flange bolt diameters and remove the 2" part of the pipe from the downpipe.

I've googled for a while and there are bolt patterns for 2.5" flanges ranging anywhere from 3" to 4.5". Do I just McDurper it and thread the bolts through both flanges at an angle? Doesn't seem right to me...is there some allowable difference between the bolt center on both flanges?
 

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ej8
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6,365 Posts
Yes, that I understand. I have both the old and new:



The larger donut is for the test pipe (came with it). The problem is how to match the flange bolt diameters and remove the 2" part of the pipe from the downpipe.

I've googled for a while and there are bolt patterns for 2.5" flanges ranging anywhere from 3" to 4.5". Do I just McDurper it and thread the bolts through both flanges at an angle? Doesn't seem right to me...is there some allowable difference between the bolt center on both flanges?
Look for one that is slotted. I used one for my setup and the bolts had lots of space to line up.
Then mate it up to the test pipe. then slot the test pipe as much as possible and the bolts should line up fine.

check the spec of this one.
SF008 2 5" 2 1 2" 2 Bolt Universal Exhaust Flange | eBay
 
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