The stupid exhaust question thread

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wirebrush

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Are headers interchangeable from TBI to Vortec or visa-versa or do they have to be specifically for 96-98 5.7L?

I'd like to know as well. I'd like to put a good single exhaust on my 97 Burb and I don't understand why it has dual pipes all the way to the muffler unlike my 93 XCSB truck. I can get a single in/single out Flowmaster for $50 on clearance at a local shop, but they don't have any dual in/single out muffler of any kind. I would like to pick up a junkyard Y pipe and fab a good single exhaust with mandrel bent pipe and the cheap flowmaster. Would that be a bad idea? Would I be better off building a true dual system off of the existing system?
 

6chevy9

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if your just wanting a new exhaust and not going all out i think you would be fine. i would get one of the dynomax y pipes from summit and convert your duals to single at the end of the intermediate pipes ( where the muffler flange mounts to the duals ) and run your single flowmaster. but if money is no problem and your going to build it up a little going with true duals like that would be pretty sweet. most of the 97 have that true dual y pipe unless it came with a 305. mine had a 305 so there was an actual y pipe no true dual. also yes the y pipe from an older tbi truck will bolt right up. atlest on my 97 it did. i put a y pipe off a 92 c3500 on it with no problems. but im also not running cats and if i remember the o2 sensors will need the bungs welded into the older y pipe.
 

wirebrush

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if your just wanting a new exhaust and not going all out i think you would be fine. i would get one of the dynomax y pipes from summit and convert your duals to single at the end of the intermediate pipes ( where the muffler flange mounts to the duals ) and run your single flowmaster. but if money is no problem and your going to build it up a little going with true duals like that would be pretty sweet. most of the 97 have that true dual y pipe unless it came with a 305. mine had a 305 so there was an actual y pipe no true dual. also yes the y pipe from an older tbi truck will bolt right up. atlest on my 97 it did. i put a y pipe off a 92 c3500 on it with no problems. but im also not running cats and if i remember the o2 sensors will need the bungs welded into the older y pipe.

Thanks for the info. I looked at the y pipes in the summit catalog and thought of going that route as that woudl probably be easiest. Would I gain anything by installing an x or h pipe between the collectors if I go that route? It seems like running duals the size of the factory piping would be overkill. Afterall the catback kits I've found are the same part for the 350 and 454.
 

6chevy9

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as far as i have read the h is supposed to add a little extra horsepower and the x should add more TQ. personally im working on going to an H pipe with true dual 2.5s but im also planning for more motor. with an all stock truck i see no reason for the hassle of true duals myself.
 

unstable

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I just ordered a set of headers for my rig. I'd like to run dual exhaust all the way back and drop the cats because I don't have to meet emissions because of the year of the truck. I was eyeballing the location of the gas tank and I'm seriously wondering how true dual exhaust throughout is accomplished...does anyone have this setup and some pictures to illustrate? thanks.
 

noremac

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if i go duals im going with an H pipe, but im pretty sure a S/I D/O set up should be about the same, probably 2.75 from cats to muffler then 3'' out to the tips.i want the truck (if i get it) to sound good but i dont want to sacrafice MPG or more importantly, low end.

i know for a fact that 1998 k1500 vortec 5.7L have true dual 2" ID pipe all the way back to dual in 2", single out 3" muffler...
 
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Heard from a mechanic buddy of mine that if I go catless and do dummy o2 sensors that the truck will run rich and I'll get no MPG improvement. Is he right? And is x-pipe placement critical? I used a laser heat gun to measure the pipes when the truck was warmed up and the hottest spot was just before the second right (looking up from ground) cat. Good place for the x-pipe? thanks.
 

bizzo15

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Is the factory exhaust system on these trucks welded or clamped? More specifically a '91 305
 

unstable

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if you get rid of your O2's, the truck will run like crap for sure. As for the cats...if your O2 sensors are before the cats, you could theoretically drop them without any ill effects (assuming you keep the O2's in place)...not sure what it will do for your emissions though. If your O2 sensors are after the cats, then I'd figure they are calibrated to take an "after exhaust has been catalyzed" reading and therefore dropping the cats would screw up the O2 readings...makes sense?
 
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