Need help with Exhaust!

[lucky_7]

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.

[TheBlueBomber]

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

[lucky_7]

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

[country29]

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.

[lucky_7]

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.

[TheBlueBomber]

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

[lucky_7]

hehe, ya, but thanks for trying bluebomber

[TheBlueBomber]

Originally Posted by lucky_7

hehe, ya, but thanks for trying bluebomber

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.

[lucky_7]

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

[Blue97]

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

[lucky_7]

Thanks blue...

[lucky_7]

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?

[1997z71]

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.

[lucky_7]

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

[1997z71]

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

[lucky_7]

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

[Blue97]

Originally Posted by lucky_7

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

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

[lucky_7]

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...

[lucky_7]

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

[Blue97]

Originally Posted by lucky_7

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

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.

[lucky_7]

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

[Blue97]

Originally Posted by lucky_7

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

Hope this helps.

[lucky_7]

Thanks, I'll go look at it now

[lucky_7]

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....

[lucky_7]

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

I did a little looking, maybe a super 40?