I finally had a chance to work on my car again tonight. I measured the width of all H-pipes involved and here’s what I found (this is the distance between both header flanges, pipe OD to pipe OD):
Stock H-pipe: 24 and 3/4”
BBK O/R H-pipe: 24 5/8”
Magnaflow: just shy of 24”
To gain the extra distance, I used my floor jack and a couple pieces of wood to add some spread. On the first attempt, I went to far and ended up at 25.25”, so I used a ratchet strap at the flanges to bring it back. The ratchet strap took about 5 conservative tried to get it right.
In addition to this, I also elongated the flange holes for the header bolts to give more adjustment on the bank 1 header.
Anyway, I just got the H-pipe bolted back in and I’m hoping for the best. I didn’t have to muscle the pipes this time, so hopefully that’s a good sign. I didn’t have time to get the O2’s back in place along with the cat-back, so I will try to finish tomorrow morning and do a quick leak check.
Thanks for all of the replies, I really appreciate the help. Cross your fingers for me!
I still wonder if this is just a symptom of having the BBK shorties, which may not be using an exact stock flange location. What headers are you guys running along with your Magnaflow H?