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Cat is cracked need advice!!

This is a discussion on Cat is cracked need advice!! within the External Engine forums, part of the LSx Technical Help Section category; My 02 WS6 has a cracked cat weld, I can hear a raspy leak and the exhaust is rattling something ...

  1. #1
    Senior Member Whamhammer's Avatar
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    '02 Trans Am WS-6, 6M

    Cat is cracked need advice!!

    My 02 WS6 has a cracked cat weld, I can hear a raspy leak and the exhaust is rattling something fierce up front. I got a quote from a good local performance shop on a header+catted Y pipe+Cat back but my budget is nowhere close to being able to do it right now (Christmas is coming and we just bought a new fridge). This is a 37 mile each way daily driver and I drive my wife and daughter in it (not as much as my wifes family sedan).

    The eventual plans call for the LS1 to get heads/cam and target over 400 rwhp and 400 rwtq with a fat power band. I am going to keep cats and the air pump on the car, so lets keep it within that scope.

    I know I can put on some OEM style, high flow Magnaflow cats , and stay in budget but that rules out LT headers down the road (unless I scrap the converter) and either put a Magnaflow cat back now, or do it in the spring. I could always buy some regular-old aftermarket cats but they don't seem much more inexpensive and probably will flow like crap and still would have to chuck them if I go LT headers.

    Would I really be leaving a ton of power on the table (now and after heads/cam) if I just went with Magnaflow cats and cat back , pick up a high flow y pipe (if cost effective) and went with stock exhaust manifolds?

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    For now, have the shop rig you up a down pipe from the manifold into a high flow cat and to your stock Y-pipe. They can use the stock converter to model the bends and angle of the flange and then tweak it during installation. They can even weld in bungs for the upstream O2 senders.

    Sorry, I sold both of my stock replacement cats a while back. Check with the other Jeff to see if he still has his.

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    Senior Member Whamhammer's Avatar
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    Quote Originally Posted by pajeff02 View Post
    For now, have the shop rig you up a down pipe from the manifold into a high flow cat and to your stock Y-pipe. They can use the stock converter to model the bends and angle of the flange and then tweak it during installation. They can even weld in bungs for the upstream O2 senders.

    Sorry, I sold both of my stock replacement cats a while back. Check with the other Jeff to see if he still has his.
    Thanks Jeff, the Magnaflows Ive seen on Summit are high flow OE style that has an O2 bung, wouldn't that mitigate the need the fabricate a down pipe and save a few hours labor?

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    Yes, if the Magnaflow unit replaces the entire piece then you would be good to go. Got a link to what you are looking at?

    This is what one of the cats looks like out of the car:


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    Senior Member Whamhammer's Avatar
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    Quote Originally Posted by pajeff02 View Post
    Yes, if the Magnaflow unit replaces the entire piece then you would be good to go. Got a link to what you are looking at?

    This is what one of the cats looks like out of the car:

    Click for full size
    I wish I did, he told me the crack was starting when I picked up the car. To be honest, I should have taken action but I knew the weld was to the outer peice and that there was an inner one too. I thought I had a month or two, not a week or two.

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    Senior Member Whamhammer's Avatar
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    Okay, I am going with with all new exhaust. Kooks headers (with air pump/secondary air), Kooks catted y pipe and Magnaflow cat back. Between this and the SLP lid and bellows, will I need a tune for this?

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    Senior Member raynor139's Avatar
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    You don't have to get one but you will run rich and you won't get the most out of it if you dont.
    Mods - Lid, Skip Shift Eliminator, MGW shifter, UMI SFCs, Founders Lower Control Arms, Founders Panhard Bar, Founders Adj. Torque Arm, UMI Torque arm mount, MWC Drive shaft safety loop, KONI Yellows, Strano Springs, Strano Sway bars, UMI Upper and lower A Arms, 160 thermostat, TSP headers and TSP true duals Monster stage 2 clutch, racetronix fuel pump, Strange S60 rear axle and tune by Frost.

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    A mail order tune from Frost would work great with that combo.

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    Senior Member Whamhammer's Avatar
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    Quote Originally Posted by raynor139 View Post
    You don't have to get one but you will run rich and you won't get the most out of it if you dont.
    Would the tune be a dyno tune, or is it a simple adjustment that doesnt take much effort for the tuner?

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    Anything that affects air flow through the engine impacts fueling. The MAF output tells the PCM how much air is entering the engine and the O2 sender output is utilized to adjust fuel trims based upon how rich or lean the exhaust gases are. A tune will dial in your fueling across the board and make whatever combination of aftermarket parts (lid, headers, etc) work much more efficiently so that you get the most out of your modifications.

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    Senior Member Whamhammer's Avatar
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    Quote Originally Posted by pajeff02 View Post
    Anything that affects air flow through the engine impacts fueling. The MAF output tells the PCM how much air is entering the engine and the O2 sender output is utilized to adjust fuel trims based upon how rich or lean the exhaust gases are. A tune will dial in your fueling across the board and make whatever combination of aftermarket parts (lid, headers, etc) work much more efficiently so that you get the most out of your modifications.
    Basically, what my question comes down to is I want to give my local shop that is doing the install my business for the tune. The guy specializes with F bodies, and can do tuning. I just dont know if this sort of tuning would require using a dyno, or if this is something that might be an hours labor or so's charge to do.

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    A dyno tune will get the most out of your parts combo as it will be based upon actual A/F readings and power across the rev range under load.

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    Stay away from the magnaflow hi flow cats, they're garbage. I've went through 3 sets of them, none of them even lasting a day. I finally got some cats that hold up, but can't think of the name off hand, they ran $125 a piece, rather then $60-80 for the pair and so far they've lasted a couple months with no issues.
    Last edited by Sas; 03-01-2016 at 12:23 PM.

  14. #14
    Senior Member Whamhammer's Avatar
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    Quote Originally Posted by Sas View Post
    Stay away from the magnaflow hi flow cats, they're garbage. I've went through 3 sets of them, none of them even lasting a day. I finally got some cats that hold up, but can't think of the name off hand, they ran $125 a piece, rather then $60-80 for the pair and so far they've lasted a couple months with no issues.
    I actually went with Kooks LT (emissions) headers and catted y-pipe.

    I did use Magnaflow for the cat-back exhaust though.
    pajeff02 likes this.

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    Member speedyWS6's Avatar
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    Quote Originally Posted by Sas View Post
    Stay away from the magnaflow hi flow cats, they're garbage. I've went through 3 sets of them, none of them even lasting a day. I finally got some cats that hold up, but can't think of the name off hand, they ran $125 a piece, rather then $60-80 for the pair and so far they've lasted a couple months with no issues.
    What was wrong with all yours???

    Mine have been fine and are still fine!



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    The first two sets blew out the internal screens within an hour of putting them on the car. The third set only blew half the guts out within an hour as well. The car has a factory tune and never had this problem before swapping to long tubes. The cats I have now look much tougher and have heat shields on them, which the manga flows did not have. They also came with paperwork, in case you need it for inspection, which the manga flows did not have. Maybe manga flows don't work well at higher altitudes. Lol.

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