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opinions needed on duals w/ cats

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Old Jan 14, 2008 | 04:27 PM
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Default opinions needed on duals w/ cats

I'm going to be buying some race style american racing headers from MPH soon. Car is a '99 Z28. I have some duals that I bought used from speed inc. that I want to hook up to the AR headers. It would hook right up, except that I want to add cats.

I did some searching and I have concluded that my best bet is to use a pair of magnaflow cats #59959. Anyone know the best place to buy them at? https://ls1tech.com/forums/showthrea...magnaflow+cats
V6 Bird in post #11 is using them. Should I have them right at the collectors or further back? How will they hook to the collectors if that the route I go- should I just have an exhaust shop weld in 2 flanges like the one in the pics? Do you think that a shop will be able to weld the duals to the cats and make it still fit before the axle. I know that the duals will need to be made shorter to compensate for the added length of the cats. I included pics of the duals. I will probably contact FLP about doing the exhaust work as I have read they are local exhaust experts. Sorry for all the questions! Thanks guys!!
Attached Thumbnails opinions needed on duals w/ cats-sweet-thunders-compressed.jpg   opinions needed on duals w/ cats-sweet-thunders-2-compresses.jpg  
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Old Jan 15, 2008 | 08:06 AM
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Those are the ones I got, supposedly one of the best flowing.
I got them on special for like $70 a piece so I got lucky.

Here's pics of where my exhaust guy put em..
I don't know if this is the optimal place, but its the logical place cause you need 8" of straight pipe with 4" of clearance.
Anyway, it can be done, but it might cost you.



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Old Jan 15, 2008 | 11:16 AM
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^^^Thanks DirtyJohn!! Looks good! Like you said it will probably cost me lot to get them to fit the cats in. I just don't want the damn gas smell. Did you have the cats welded into existing duals? or was is made from scratch?
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Old Jan 15, 2008 | 11:23 AM
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It's the TSP TD kit modified by a guy with a welder in his garage.
Lets say $200 for the cats, and whatever it'll cost the shop to chop and weld it up should be your final.
I don't think I would take the kit to them and have em put them in off the car cause the kit might not fit right after that. Maybe install the kit and bring it to them then.
Should quiet it down a bit and reduce the smell.
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Old Jan 15, 2008 | 11:26 AM
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Should get it w/o cats first. I don't ever notice the gas smell w/ my TD setup, but maybe it bothers some people more than others.
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Old Jan 15, 2008 | 11:35 AM
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I got mine from EAD Performance. Good guys over there and the Magnaflow cats are great. Very pleased.


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Old Jan 15, 2008 | 11:51 AM
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what about these cats? any good?

http://cgi.ebay.com/ebaymotors/LS1-L...2em118Q2el1247
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Old Jan 15, 2008 | 12:40 PM
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Originally Posted by DirtyJohn
It's the TSP TD kit modified by a guy with a welder in his garage.
Lets say $200 for the cats, and whatever it'll cost the shop to chop and weld it up should be your final.
I don't think I would take the kit to them and have em put them in off the car cause the kit might not fit right after that. Maybe install the kit and bring it to them then.
Should quiet it down a bit and reduce the smell.
Thats a great idea! Thanks!

Originally Posted by Soul TKR

I like the price on those!! But they probably don't flow as well as the magnaflow's, and I want these to be as small as a restriction as possible.


Thanks for the pics Chocotaco! They look like a very straight through design!
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Old Jan 15, 2008 | 12:55 PM
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I have TSP duals with cats, as well.

You want to have the cats as close to the collector as possible. My passenger side is right off the collector and the driver's side is like 3 inches back.

Also, the shop that did the work (EXTREMELY good place and guys in San Diego) made the cats removable so I can switch them out at any time.


I think total was exactly $200 for cats and somewhere under $200 for labor (cause I wanted them removable). I think I got a helluva deal considering how easy it is for me to change them in and out....
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