Replace 1 7/8" pipes by 2 1/4" on a 6 cyl.

[Dart/Valiant]

Looking under my car and taking a few measurements, I saw that I have a 2¼ O.D. front pipe. which narrows to 1 7/8 where the catalytic converter is welded. Could we start from the front pipe and continue this up to 2¼ all the way back?

Do you see any side effects to doing this? I would also remove the catalytic converter, (legal for such an old car where I live). Does this have any significant value?

 

[RustyRatRod]

You can, but there won't be much benefit unless you enlarge the exhaust manifold outlet to 2.25" as well. I enlarged mine to 2.5 and ran the TTI 2.5 exhaust. It made a big difference.

 

[Dart/Valiant]

How did you enlarge the outlet?

 

[RustyRatRod]

How did you enlarge the outlet?

I actually didn't. I took it to my friend Freddie right down the road, because I SUCK using a hand grinder. He's a master with one. I've had him do two for me and one for someone else. He does a really nice job. This one is 2 1/4", but the one I am running now he got out to 2 1/2". I never would have thought there was that much meat in the manifold in that area, but it turns out it's a lot thicker than it appears.

Exhaust Manifold Mod

 

[Dart/Valiant]

I read the Exhaust Manifold Mod, great work! But still wonder what tool he put on his hand grinder.

 

[RustyRatRod]

I read the Exhaust Manifold Mod, great work! But still wonder what tool he put on his hand grinder.

I can tell you exactly what he used. He used this with about a 1" x 1" cylindrical rock on the end then finished it up with a flapper wheel.

Pneumatic 1/4 in. Die Grinder with 3 In Extension

 

[Dart/Valiant]

UPDATE:
Finally, the front pipe was not 2¼ except for a part ahead of the catalytic converter.
Now received 2¼ everywhere, the cata was sold to partially finance the operation.
Yes, we have a difference! Can feel more torque, acceleration with less effort.

Looking under my car and taking a few measurements, I saw that I have a 2¼ O.D. front pipe. which narrows to 1 7/8 where the catalytic converter is welded. Could we start from the front pipe and continue this up to 2¼ all the way back?

Do you see any side effects to doing this? I would also remove the catalytic converter, (legal for such an old car where I live). Does this have any significant value?

 

[diymirage]

Did you hog out the manifold aswell?

 

[kesteb]

The biggest help is going to a 2 1/2" exhaust pipe. Grinding out the exhaust manifold output is good for aesthetics.