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Old 12-29-2017, 11:35 AM   #1
HeavyD
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Exhaust help! 5.7 vortec plugged cats..worth paying for larger diameter replacement??

So I bought a pretty clean (for here anyway, no rust etc) 98 z71 with the 5.7. Got a PO430 code and after replacing the O2 sensors friend suggested it is time to replace the cats which have lived for 277000km.

I know the factory piping is pretty tiny, but is it worth it to have a slightly larger set fabbed up? Can find stock replacement easy enough, but nothing larger, say like a 2-1/4. Would there be any real gains?

Headers worth it? It is a winter daily driver so I am not sure how much I want to spend on this thing yet. Other than changing out the poppet injector arrangement it won't see any engine mods.

Looked into a 3/4 ton setup which is larger, but shops here say it can't be used as it is different, even though the truck body and engine is the same? confused..

So is it worth it to spend some coin in this area? Having a shop fab a complete system up will prob be over $1000. Stock replacement of bad area about $500.

Anyone?
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Old 12-29-2017, 12:11 PM   #2
Malo83
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Re: Exhaust help! 5.7 vortec plugged cats..worth paying for larger diameter replaceme

Go with Magnaflow cats, they flow the best, have a 3" single exhaust on my 83 with a Magnaflow.
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Old 12-29-2017, 04:18 PM   #3
b454rat
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Re: Exhaust help! 5.7 vortec plugged cats..worth paying for larger diameter replaceme

I don't see how it is different. I had a 99 CCSB that had a 350 and bigger pipes. Now I have a 98 Tahoe with smaller pipes. Maybe their thinking the bigger pipes will flow at higher Rs than the smaller pipes. I had headers on the crew, and shows the same thing for all vortecs, 'hoe or crew....but for a snow beast be kinda pointless....
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Old 01-02-2018, 04:45 PM   #4
Tom
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Re: Exhaust help! 5.7 vortec plugged cats..worth paying for larger diameter replaceme

Bigger setup works fine your shop is dumb. On a totally stock 350 I doubt you'd see much from larger pipes, but long tube headers do help. Again, not really worth it for a stock winter beater in my opinion, ice and snow kinda slow things down regardless of engine output.
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Old 01-05-2018, 07:15 AM   #5
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Re: Exhaust help! 5.7 vortec plugged cats..worth paying for larger diameter replaceme

Magnaflow metal matrix cat was worth the cost for me. Put it in front of a Flowmaster cat-back system. It does let a little more sound through, too.
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Old 01-07-2018, 03:13 AM   #6
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Re: Exhaust help! 5.7 vortec plugged cats..worth paying for larger diameter replaceme

Thanks for the replies, all are appreciated!
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