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Thread: taking off the cat

  1. #1
    Vamos Mantequilla!!! ProfessorKaos's Avatar
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    taking off the cat

    My 91 with a 4.3 still has the stock exhaust system, its all rusted together and has 136,000+ miles on it. I was wondering if I took of the cat would it improve perfromance or mpg since it is probably clogged.

  2. #2
    Registered User S1088327's Avatar
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    well if you take that off it will open your exhaust up and flow better but you wont notice much power increase..... and with having 136k on it, it can still be good and not give your problem
    Part 1 70 Chevelle 250 to 305 sweet street car 13sec.s at 110mph R.I.P. to the new owner of it New York!!!:bang:
    Part 2 88 S10 2.5liter to a 327SB UNDERCONSTRUCTION!!!!! :bowdown:
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  3. #3
    Vamos Mantequilla!!! ProfessorKaos's Avatar
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    Well turns out that I left the cat on, but the muffler is off. I will be putting true duals on, but dont know what mufflers to go with. I'm open to suggestions.

  4. #4
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    deninatly go with a Flowmaster 40 series muffler. They sound GREAT.


    89' S10 blazer 4wd: 355, 650 dp, rpm intake, comp 282 roller cam, modified vortecs, T56 Six speed, 8.8 ls rear, headers, x-pipe, spintech pro street mufflers, and......AC

    Blazer burnout video - http://www.youtube.com/watch?v=sP7iLypoDI4

  5. #5
    Registered User S1088327's Avatar
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    agree Flowmaster 40 Series!!! sweet sound
    Part 1 70 Chevelle 250 to 305 sweet street car 13sec.s at 110mph R.I.P. to the new owner of it New York!!!:bang:
    Part 2 88 S10 2.5liter to a 327SB UNDERCONSTRUCTION!!!!! :bowdown:
    HOLLA AT YOUR BOY!!!!!
    Scott C.
    :blazer:

  6. #6
    San Clemente's Finest GMC MAN's Avatar
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    I do agree also that Flowmasters sound better, but after comparing many opinions of PERFORMANCE Magnaflow is the way to go. Granted I never owned a Flowmaster pipe, but Magnaflow has the straight thru design with no baffles and offer better flow and definately sound awesome too... Just not quite as rumbly as Flowmaster. But I read in a hotrod book that louder doesn't always mean better..... My brother has Dual Flowmaster with an H pipe on his 98 z28 and can't stand the sound of it. I love the way it sounds but when you have to drive it every single day that loud obnoxious sound gets old....


    Magnaflow!!
    Last edited by GMC MAN; 01-04-2004 at 12:36 PM.
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    oh and fart pipes too......

  7. #7
    ride the spiral SoulsAflame4135's Avatar
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    do gibson, just to be different

  8. #8
    Registered User Catching Second's Avatar
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    This is said so many times on this forum and the Engine and Driveline forum that it should become a sticky

    Taking out the catylitic converter will flip the SES (Service Engine Soon) light on. The catylitic converter reduces the level of o-zone killing gasses in your exhaust. If you take it out the O2 sensor will detect it and throw the light on. That is unless you get an O2 simulator.
    "A true hotrodder wouldn't be content untill he had created a car so violent, so hairy, so totally sick that the very act of dropping the hammer would result in instant death. Anything less results in the need to go faster." - Tony DeFeo

  9. #9
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    i had 2" true duals with 40 series flowmasters and no cats on my 91 blazer for 5 years and never had a problem with any check engine lights or anything because it was pre-OBD & OBDII. I will say it ran slightly better overall with the single 2.5" exhaust, no cat, and 40 series flowmaster I had on before. Better mileage with the duals, though.

  10. #10
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    2 years later....................



    Even on OBD1 systems it will most likely throw a code (not always)

    It will trow an egr code if you have a weaker egr. Some can get away with it some cant, just depends on the vehical.


    89' S10 blazer 4wd: 355, 650 dp, rpm intake, comp 282 roller cam, modified vortecs, T56 Six speed, 8.8 ls rear, headers, x-pipe, spintech pro street mufflers, and......AC

    Blazer burnout video - http://www.youtube.com/watch?v=sP7iLypoDI4

  11. #11
    Registered User AciDBatH666's Avatar
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    Wow this is an old post.

    For the record. NO you WILL NOT THROW A CODE in your 91. 91s have only one 02 sensor, and it is BEFORE the cat.

    on my 90, I took off my cat, threw a Flowmaster 40 series where the cat was, and just put a turndown. NEVER had a code thrown for it. ANd ppl swore I was running a smallblock.

    On my 95 blazer, i did the same thing. When I bought the truck I looked to see if there was an 02 Sensor after the cat. Saw there was only 1 and it was before it, so my plans were to ditch the cat, and throw another 40 series right where the cat went and dump it.
    Flowmaster is made more for sound, Magnaflows and even the Raven mufflers from Midas are a better straight thru design and will be better for performance. The Flowmaster still sounds SICK tho. Im debating on going with a Ravin because I hear they are deeper sounding. Havent heard one on an S10 yet tho.
    95 CPI Blazer, 2/3 Drop, 3.42 gears with LOCKRite Locker, no cat,Flowmaster turndown, 275/60 meats in rear,K&n PVC intake,B&M shift kit and transmission cooler, Lakewood Traction bars,Edelbrock headers, MSD ignition/wires/coil, Efan, 16.0@83mph/ 2.21 60'
    Awaiting install-Vette Servo, 75 shot NX kit, Pulleys, ADS chip,Roll Pan
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  12. #12
    Vamos Mantequilla!!! ProfessorKaos's Avatar
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    Woah, this has to be my very first post. I did end up throwin on true duals but had 50 series mufflers, but I cant remember if it threw a code or not...

    '93 bodied Std. Cab....Classick
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  13. #13
    BLF #1 BITCHES! slow 89's Avatar
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    this has nothing to do with anything.. but ill post it anyways.. i took the cat off my 99 sonoma and put a pipe thru the orig cat.. *from the bottom it looks like a reg cat*.. and i have yet to throw a SES code.. just depends how bad your motor polutes.. and its odb2 :smoker:
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  14. #14
    Do ya feel lucky? Teeleton's Avatar
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    I prefer a Dynomax Ultraflo for performance (and sound). It's also pretty much straight through. I've had one on my blazer for the past 2 years. It was a little obnoxious at first, but then it mellowed out a bit (or I became deaf, both are equally likely).

    Teeleton
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  15. #15
    Zombie Killer 6SpeedBlazer's Avatar
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    Originally posted by slow 89
    this has nothing to do with anything.. but ill post it anyways.. i took the cat off my 99 sonoma and put a pipe thru the orig cat.. *from the bottom it looks like a reg cat*.. and i have yet to throw a SES code.. just depends how bad your motor polutes.. and its odb2 :smoker:
    my buddie did the same thing, his catalyist was ratteling real bad so he gutted the cat and has yet to throw a code and that was about 8 months ago and his is obdII also

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