Need help with Exhaust!
 

Hey guys,

I need a little help installing exhaust for my 98 5.7 ext cab sierra. Currently Im looking at a flowmaster super 50 series , 2.25'' dual in/3.00'' center out with a turn down. I just need to know the stock exhaust size coming from the cats so can buy the right adapters. Later I plan on doing some engine mods and going with headers and true duels with and x pipe and 2 flowmasters.

Re: Need help with Exhaust!
 

I believe stock exhaust is 2 1/4" all the way through. That was what was on my '96 when I bought it.

Re: Need help with Exhaust!
 

thanks, guess i could use my calipers to measure the outside and subtract the wall thickness......duh :crazy:

Re: Need help with Exhaust!
 

my 97 ecsb Z71, right at the dual inlets of the stock muffler each pipe is 1 7/8", i'm sure its same up to cats. 2" id to 2.25" adaptor will leave a small gap to fill with the welder on the original pipe.

Re: Need help with Exhaust!
 

Yup, I measured them earlier and they are 1 7/8", from the muffler to the cats and I'm sure they are the same to the manifolds.

Re: Need help with Exhaust!
 

Thank God you didn't listen to me then haha.

Re: Need help with Exhaust!
 

hehe, ya, but thanks for trying bluebomber

Re: Need help with Exhaust!
 

My manager always says... "It's not about if you win or lose, It's how you prepare for the game".....

I guess I made him proud on this one. :lol:

Re: Need help with Exhaust!
 

Anybody know of a store bought y collector that will fit on the pipes behind the cats?

Re: Need help with Exhaust!
 

You will probably have to have it made at the muffler shop of choice...Ive looked for a y pipe... If your going to change it later why not just wait and do it then?

I went and replaced the front pipes with a flowmaster kit and high flow cats, now im adding this. http://www.summitracing.com/parts/wlk-54020 and two Aerochambers dumped over the rear axle...........


Im running a DI/SO flowmaster 50 series now.... Me no likey

Re: Need help with Exhaust!
 

Thanks blue...

Re: Need help with Exhaust!
 

Does anybody now if I can completely remove the cats from a 97 5.7 liter, I can only see one set of o2 sensors in front of the cats, and I have been told that its okay like that. But Ive also been told the truck will still run a little rich with the cats removed?

Re: Need help with Exhaust!
 

On my 97,I went with the 50 series then 4" chrome tips out the back,way too loud for a stock engine. Have since added baffles in the 4" tips,now it sounds good. Didn't notice any change in performance or mpg.

Re: Need help with Exhaust!
 

where were your o2 sensors at before, and did you remove the cats?

Re: Need help with Exhaust!
 

I left them on. I wouldn't remove them unless they're going bad.

Re: Need help with Exhaust!
 

what about high flow cats? truck has 120k on it now and since im already here i might as well replace them right...

Re: Need help with Exhaust!
 

Yes........ I installed the Flowmaster kit and have seen improvements in sound and HP, Not a lot but its noticeable.

Re: Need help with Exhaust!
 

thanks guys,

Well i found a 50 series delta flow the other day in the junk yard, paid 35 dollars for it, it 3''in/3''out, so im not ever sure in i can use it without having a custom y pipe made to come from the cats to the muffler.

If I were to buy a high flow cat at 3''in/out, I could just have them y it at the bottom of the drop pipes and tuck the cat nicely, then I could (weld this myself) extend 3'' pipe straight back to the flow and put a turn down on it....

I would get both a new cat, and a new muffler, for around......let see

100.26 +tax for the cat
35.00 for the muffler
maybe 100. to install

thats only 235.+/- for a complete system...

Re: Need help with Exhaust!
 

Anybody have a diagram of the o2 sensor locations on my truck?

Re: Need help with Exhaust!
 

I'm at work but let me see what I have on the comp at home. I just did all 4 of mine . Pretty simple , just a plug and play deal.

Re: Need help with Exhaust!
 

Okay thanks, Ive looked for them behind the cats, and i cant see them anywhere, just one on each down pipe...

Re: Need help with Exhaust!
 

Hope this helps.
http://i223.photobucket.com/albums/d...psc8bbc0df.gif

Re: Need help with Exhaust!
 

Thanks, I'll go look at it now

Re: Need help with Exhaust!
 

Well I found them, I have four, :(, so no high flow cats for me, I'll just put on a nice flowmaster with aggressive sound to overcome the restriction from the cats....

Re: Need help with Exhaust!
 

What's a good aggressive sounding flow for the 5.7 Liters?

I did a little looking, maybe a super 40?