High flow cats won’t fit on stock manifolds

[mjstruck]

Hey guys, I’m installing high flow cats and for some reason they don’t fit the stock manifolds. The opening of the cat is the right size and meant for the stock headers but it won’t go over the stock “tube/pipe” where it slides in to allow the flanges to connect and and the v band to clamp on. Has anyone had issues with this? I bought the cats used from a trusted seller and he had no issues and they look perfectly fine. He said he had a Belanger exhaust and the cats could be Belanger but he’s not sure but they also look like they could be random techs, no flex pipe and no hangers. Not sure if I should try bending in the stock piping so the cat fits or have a shop shave the opening of the cats. I literally need a millimeter or less for it to fit perfectly. And help or advice would be greatly appreciated. Thanks in advance!

[river rat]

You can rent a pipe expander from local auto parts and use it.

[mjstruck]

You can rent a pipe expander from local auto parts and use it.
Thanks for the info! I’ll look into that since bending the manifolds would be last resort since I don’t want to restrict any airflow.

[Steve M]

Either rent a pipe expander, or just buy one from Harbor Freight. If you can't get it to move enough by hand, hit it with an impact.

I had to do that on my driver's side high flow cat that I got from Belanger...passenger side fit just fine, but the driver's side was too small to fit over the exhaust manifold exit. A pipe expander was all that was required to make it finally fit after screwing with it for a few hours.

[mjstruck]

Either rent a pipe expander, or just buy one from Harbor Freight. If you can't get it to move enough by hand, hit it with an impact.

I had to do that on my driver's side high flow cat that I got from Belanger...passenger side fit just fine, but the driver's side was too small to fit over the exhaust manifold exit. A pipe expander was all that was required to make it finally fit after screwing with it for a few hours.

Thanks Steve! Glad to know I’m not the only one with this issue and will pick up an expander tomorrow.