90 manifolds - modified? Pics inside- need to mate to Flowmaster Exhaust

[Corvette95]

So starting a new thread as I posted this in my other long thread I have going but not getting much attention. So unexpectedly, I had to pull my stock headers and Flowmaster cat back system to replace my motor mount and C-Beam plates.. I am going to bite the bullet and replace the headers with OBX because that was a planned future upgrade but the stock ones being such a PITA, I have them ordered now, can't spend the money on the Corsa catback that I want right now, so I need to mate the OBX's to the old Flowmaster, seems there is an issue on the right side, a prior modification? What do I need to do to get the two connected, car is up on stands and really can't get it to a trans shop, help and part ideas would be appreciated. Also, do I reuse the OE header stud that does into the oil gallery (resealing of course) I have new header bolts ordered. (seems the right exhaust has a flange added?) Thanks.

[tccrab]

Flange has definitely been added. The stock configuration for a '90 is flange on drivers side and slip fit with a clamp on the passengers side.
You have two options.
Install the headers and drive it with open exhaust to a nearby muffler shop. Although this would be fun, your local constabulary would take offense if they caught you.
Install the headers, get out your tape measure and digital camera, and calculate precisely how much to cut off the flowmaster catback, and have flanges welded on. Then pray to whichever deity appropriate for such endeavors, and bolt it up.
Hopefully it will be close enough so that you can then drive it down to the muffler shop for adjustments it will definitely require.

Of course, you could just install the headers and then have it towed on a flatbed to the muffler shop, but where would be the fun in that?

Crabs

[Ccmano]

That flange on the right exhaust manifold is OEM stock. I can show you pictures of two I've done in the past few years that are identical. It's the OBX headers that are not designed to mate with the stock exhaust. I did OBX headers on my car and had the exact same issue. You have to have an adapter piece fabricated for the headers to mate with the flange on the exhaust. Similar to what your seeing on the OEM manifold. Or... you can cut the flange off the exhaust and use commonly available exhaust pipe adapters to mate the headers to the exhaust. I've done it both ways.
H

[Corvette95]

Originally Posted by tccrab

Flange has definitely been added. The stock configuration for a '90 is flange on drivers side and slip fit with a clamp on the passengers side.
You have two options.
Install the headers and drive it with open exhaust to a nearby muffler shop. Although this would be fun, your local constabulary would take offense if they caught you.
Install the headers, get out your tape measure and digital camera, and calculate precisely how much to cut off the flowmaster catback, and have flanges welded on. Then pray to whichever deity appropriate for such endeavors, and bolt it up.
Hopefully it will be close enough so that you can then drive it down to the muffler shop for adjustments it will definitely require.

Of course, you could just install the headers and then have it towed on a flatbed to the muffler shop, but where would be the fun in that?

Crabs

Thanks for confirming what I thought....muffler shop is close, I will stop in Monday and see if they are willing to take the job. What heat shields are reused in headers, the only one I think is a body shield on drivers side that seems to shield the master cylinder line ( I know not any of the actual manifold shields go back on). I am going to try titanium header wrap , never used it before....