Question about JBA High Flow Cats fitment with Flowmaster American Thunder Catback - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

TCAT · 11-06-2011, 09:55 AM

I am about to buy JBA high flow cats for my car. Right now, I have the Flowmaster American Thunder Catback that is 3", and obviously the stock manifolds are 2.5". I have the stock headers because my car is Turbocharged. So, would I need the JBA cats that are 2.5" at the manifolds but 3" where it connects to the 3" catback, ORRR would I need 2.5" for the manifold (same as the other option) and still 2.5" where it connects to my catback?

I've been told by a few people that the American Thunder catback (even though 3" throughout) necks to 2.5" where it connects to the cats. So, that would believe I would just need the 2.5" to 2.5" high flow cats, and not the 2.5" to 3" cats. Then again, some people tell me something totally different.

So, is there anyone that actually knows which size I need to get

. Thanks.

The Stig · 11-06-2011, 10:38 AM

JBA makes high flow cats that are 2.5" to 2.5" , 2.5" to 3" , and 3" to 3"

TCAT · 11-06-2011, 12:14 PM

Thanks Steiger, I noticed that as well.

I think the problem is that I keep getting conflicting advice as to whether I should get the 2.5" to 3", or the regular 2.5" to 2.5". Some vendors are saying that the American Thunder catback (which is 3") has a 2.5" neck down area to attach to 2.5" cats. So, that would mean I could buy the cats that are 2.5" to 2.5". Then others are saying the catback doesn't neck down to 2.5", and that means I'd have to buy the cats that are 2.5" to 3".

Damn, this is confusing haha.

The Stig · 11-06-2011, 01:10 PM

easiest way IMO, and this is what I did when I had my JBA 3" exhaust, is to buy the 2.5" to 2.5" cats and then IF the exhaust doesn't bottle neck down to 2.5" your exhaust shop can fab up an adapter in about 30 minutes.

SlingShot · 11-06-2011, 01:41 PM

Get the 2.5 in, Flowmaster are 2.5 in then goes to 3.0 ...

TCAT · 11-06-2011, 02:04 PM

Quote:

Originally Posted by stieger

easiest way IMO, and this is what I did when I had my JBA 3" exhaust, is to buy the 2.5" to 2.5" cats and then IF the exhaust doesn't bottle neck down to 2.5" your exhaust shop can fab up an adapter in about 30 minutes.

Quote:

Originally Posted by SlingShot

Get the 2.5 in, Flowmaster are 2.5 in then goes to 3.0 ...

Perfect! Thanks guys'. I'll get the 2.5" inlet/outlet. I really appreciate it, and have a great rest of the weekend.

11-06-2011, 09:55 AM	#1
TCAT Drives: Has Wheels Join Date: May 2011 Location: On Earth Posts: 5,553	Question about JBA High Flow Cats fitment with Flowmaster American Thunder Catback I am about to buy JBA high flow cats for my car. Right now, I have the Flowmaster American Thunder Catback that is 3", and obviously the stock manifolds are 2.5". I have the stock headers because my car is Turbocharged. So, would I need the JBA cats that are 2.5" at the manifolds but 3" where it connects to the 3" catback, ORRR would I need 2.5" for the manifold (same as the other option) and still 2.5" where it connects to my catback? I've been told by a few people that the American Thunder catback (even though 3" throughout) necks to 2.5" where it connects to the cats. So, that would believe I would just need the 2.5" to 2.5" high flow cats, and not the 2.5" to 3" cats. Then again, some people tell me something totally different. So, is there anyone that actually knows which size I need to get . Thanks.

11-06-2011, 10:38 AM	#2
The Stig knows 2 facts about ducks Drives: ...and they're both wrong Join Date: Aug 2009 Location: The HMS Invincible Posts: 25,072 View My Garage	JBA makes high flow cats that are 2.5" to 2.5" , 2.5" to 3" , and 3" to 3" __________________

11-06-2011, 01:10 PM	#4
The Stig knows 2 facts about ducks Drives: ...and they're both wrong Join Date: Aug 2009 Location: The HMS Invincible Posts: 25,072 View My Garage	easiest way IMO, and this is what I did when I had my JBA 3" exhaust, is to buy the 2.5" to 2.5" cats and then IF the exhaust doesn't bottle neck down to 2.5" your exhaust shop can fab up an adapter in about 30 minutes. __________________

11-06-2011, 01:41 PM	#5
SlingShot Drives: 2012 ZL1 - #670 Join Date: Jun 2009 Location: Seminole, Fl. Posts: 8,009	Get the 2.5 in, Flowmaster are 2.5 in then goes to 3.0 ... __________________

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11-06-2011, 12:14 PM	#3
TCAT Drives: Has Wheels Join Date: May 2011 Location: On Earth Posts: 5,553	Thanks Steiger, I noticed that as well. I think the problem is that I keep getting conflicting advice as to whether I should get the 2.5" to 3", or the regular 2.5" to 2.5". Some vendors are saying that the American Thunder catback (which is 3") has a 2.5" neck down area to attach to 2.5" cats. So, that would mean I could buy the cats that are 2.5" to 2.5". Then others are saying the catback doesn't neck down to 2.5", and that means I'd have to buy the cats that are 2.5" to 3". Damn, this is confusing haha.