I am looking at headers so should I keep the catalytic converters? I can buy a set of Thorley ceramic coated headers for around 530 dollars which is half the cost of Dynatech. If I went with the Thorleys I will install them and just take them to a exhaust shop to bend some pipe for them. I am getting a Nelson tune so I could just have Allen shut off the circuits so I wont throw any codes. But if I take the cats off will it make my truck sound like ****? I have heard that some people that take their cats off makes their truck sound terrible (I have a Borla muffler). I will also get a stall to make up the low end loss with my cam so I am not concerned about losing any with the removal with the cats. Thanks for the input in advance.

Also I live in central Illinois and we dont have any check stations around here for exhaust systems.

 

Not sure about the sound quality but it will make it louder.
Hmm, I thought all of Illinois had smog checks. Learn something new everyday.

 

They do but it is all up by Chicago

 

Unless you are planning on going all out with FI or a big cam I would just leave the cats on. You may only gain about 10rwhp from it if all you have is basic bolt-ons. IMO it's not worth the nasty sound they make when they are gutted.

Now with a supercharger, turbo etc......

 

i went without cats on mine when i put on the asm's. then i put on the juice and wow. what a difference. now that she is down again i am putting the cats back on. i am going to carsound free flow cats.

 

I have dynatech system on mine...headers and their cats. I have been working on a lean misfire issue which causes a rich condition (extra rich) in the exhaust, this has in short...blown...errr torched my cats. They no longer exist. Sounds like ****.

I have to keep cats due to emmissions around here, but to answer your question on my end...without sounds horrible unless you have something to resonate them...and if you do...then what's the purpose. I agree with F8L Z71. What are your mods? Do you need all that flow? Fooling the computer to beleive they aren't there could lead to more problems than they are worth. Maybe, maybe not. IMO

 

like F8L said, if you plan to get some good mods (nitrous, big cam, etc) then do it now, so you can get it over with and wont have to mess with it later.

If you are just getting a cold air intake and a muffler, leave them on.


On a relatively stock truck, removal of cats will result in loss of some low-end grunt.

 

F8L z-71..........when is 10 hp nothing?......i gutted mine and my top end came alive. my exhaust really rumbled after that. i would say go for it. Why would u want a high flow muffler & headers when u still have no flow threw the cats. either high flow cats or none at all. thats my imput.

 

10hp to me is nothing when compared to the smell (when not tuned correctly) or the raspy sound you get from having no cats on an LS1.

If your top end came alive then I would venture to say your cats might have been going out as it was, or you had a lean problem. I have done gutted cats on all 3 of my different LS1 based cars and on 2 of them it made a decent difference but on the truck it was a waste until I did the big cam.

When you remove the cats you must retune the truck to get the LTRIMS back in line and to get the most benifit you must turn COTS off also. Do all that then it is worth it. Just gutting them and calling it good is a bad idea IMO.

Just my opinions, doesn't mean i am right

 

I like the sound of mine.

Thorleys
gutted cats
3 inch, into a PV muffler.

Be sure you have some sort of tuning. It knocked my readings way out of wack.

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oh....yeah, f8l has it about right.