2015 5.3 header/y-pipe w cats kit

2015 High Miler · January 24, 2021

I have 2015 Sierra stock (for now) 5.3 w 200,000 miles. I want upgrade to headers and hi flow cats to replace a cracked manifold.

I’m seeing a range in prices from $299 for just headers to $1800 for a complete system. I was quoted $950 from a local shop installed, w cats and o2 extenders.

I’m not really thinking I NEED stainless due to age of truck and the mostly mild environment I live in. But I don’t want it to come apart and need repairs often either. Im looking for a good value for performance/durability system.

For those of you with experience, can you point me in a good direction as far as what’s what?

for the record, I tried a search but it was in conclusive.

Thanks

langston1726 · January 24, 2021

I’ve had Texas Speed long tubes and catted Y on my 2015 for couple years now. All stainless and fit is great. They are an excellent value for the cost compared to the other 304 stainless options. There’s a company called CFM engineering (sold by KHP performance) that just released some stainless headers for our trucks as well. Not sure on price and fitment but they look right up there with a Kooks as far as design and quality. I know people that have also had good experience with the Speed Engineering headers. I don’t believe they have a catted option though.

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flyingfool · January 25, 2021

dont waste time buying an exhaust if you dont tune for it, why bother freeing up the flow if your gonna run cats?

doug thorly uses thick flanges on his stuff. is made in USA unlike the cheapo headers

this kit has the tri y long tubes with connection to muff

http://www.dougthorleyheaders.com/thy-352y-l-c--2014-2019-chevy-silverado--gmc-sierra-5.3l-v8-long-tube-tri-y-headers_15752

Edited January 25, 2021 by flyingfool

CamGTP · January 25, 2021

Cats aren't a big enough restriction at this power level, won't make any noticeable difference if he runs them.

Edited January 25, 2021 by CamGTP

2015 High Miler · January 26, 2021

Thanks for the opinion on the cats.

it’s a daily driver and I was Thinking the cats would keep it legal and tone down the sounds “some”. I’m not locked on having them though.

flyingfool · January 27, 2021

On 1/25/2021 at 2:03 PM, CamGTP said:

Cats aren't a big enough restriction at this power level, won't make any noticeable difference if he runs them.

would you agree they clog up when power is applyied to them and more fuel added to the motor? they tend to melt internallly from the high heat and glaze over the ceramics inside, cant this can cause restriction?

Edited January 27, 2021 by flyingfool

flyingfool · January 27, 2021

On 1/25/2021 at 6:42 PM, 15 hi miler said:

Thanks for the opinion on the cats.

it’s a daily driver and I was Thinking the cats would keep it legal and tone down the sounds “some”. I’m not locked on having them though.

if your tuning it... I would be curious how much power you make with a stock muffler, and the flapper removed, with long tubes installed no cats., that would be my route , emmisions is not important since there is no smog on new vehicles for several years, just keep the stock exhaust in storage til emmissions time ..

Edited January 27, 2021 by flyingfool

CamGTP · January 27, 2021

If that was the case then GM, Ford or Dodge wouldn't be able to run 500-700+ horsepower through them. All three of those companies run supercharged and turbocharged engines with considerably rich factory air fuel ratio's without hurting the cats. Those engines also make much higher EGT's than a NA 5.3 or 6.2 engine.

You'd have to do something really wrong to destroy the cats. Like run 9.0 AFR all the time or run timing near zero or lower to super heat the exhaust and melt stuff.