jtm1968

Hi Everyone,

I was planning to buy a set of catted ARH headers/x-pipe for my C6 Z06 but a local tuning shop in Utah informed me that they will not pass emissions, especially because the state is starting to get more stringent with respect to emissions inspections. I have been told that Kooks Green Cat System is the only header system that is EPA approved/legal, but they are pricey at over $3k. Is it worth it? If not, is it even worth modding the car at all without headers?

I look forward to hearing everyone’s opinions.

449er

Kooks does make the best aftermarket catalytic converters however the Z06 factory manifolds flow pretty well so is it worth it to drop 3k+ ( and the cost of a tune) for a 20 something hp gain? That's your call

furious427

It all depends on how far you plan on going with mods. Do you plan on doing heads and cam later on down the road?
Another factor is are you doing the work yourself or having a shop do the work?
And as you know you will also need to tune.

jtm1968

I was planning to do ported heads, cam, intake, throttle body, tune, etc. What I’m really asking is if all that other stuff will fail to provide the same gains as it otherwise would if I don’t add LTs.

I would be doing the work myself. The entire exhaust is currently out of the car for a clutch replacement, which is why I’m considering upgrading the exhaust now.

jerseydrew

only you can answer the cost per hp gain question. but with cam and heads the headers will provide significant gains. with nothing else done i wouldn't waste my time or money. if you are at that point and doing work yourself at least do the exhaust, cold air intake and cam with tune for now. then later upgrade everything else. you may be happy with just the 100-ish hp bump of a cam, intake and headers.

Kevin Mason

Correct me if I am wrong, but doing that stuff also might cause you to fail emissions, depending.

From what I understand, and keep in mind, I know just enough to be dangerous, I wouldn't do the exhaust by itself. In fact, headers aren't strictly necessary with a very mild cam/ported heads, although they will help. You still will need a tune with cam/heads.

Dj_or_dj

Once the physical location of your catalytic converters has moved it is no longer considered “legal”

the only headers that are legal
are shorties.

jtm1968

so I guess the real question is: is it even worth it to do ported heads, cai, ported msd intake and a cam if you leave the factory exhaust intact? How much power and torque would be left on the table by skipping the LTs but doing the rest?

Dj_or_dj

Okay so now you are asking the right questions.

there are some work arounds to this.


As far as heads go. Trickflow specialties has CARB legal heads that flow more than ported OEM garbage does from a smaller chamber. And cost no more than $3500. The work around would be those heads and supercharge the Z06 with a CARB legal A&A kit and those Trick flow heads. Running no more than 5psi and you’re good.

Unless you want to do a cam swap every two years lol

jtm1968

How would this setup compare to a traditional 600whp hci N/A setup?

Am I to understand that changing heads and cam will cause the car to fail emissions? I definitely haven’t heard that from the local tuners. Mostly just concern that emissions testers are being forced to start taking pictures of the stock cats and submitting them to the authorities (EPA?)

Dj_or_dj

Yes and no,

Carb compliance is carb compliant Heads No.

anything that has a carb # will not cause the car to fail emissions. Our cars are not emissions tested. Its obd-ii tested.

BUT…. having a Tune will cause a yes flag.

Now again A&A is the only carb compliant company that offers a tune that will not fail.

As long as you have a CARB O.E. # you are good.

so if you can find a carb legal / compliant cam intake and headers … you are good

CAM possibly.
Headers Yes.

BuckeyeRay

For anyone not from the Kooky People's Republik of Kalifornia, CARB is California Air Resources Board and has zero authority outside the state.

Dj_or_dj

you are right … but if the parts are stringent enough for California’s laws …

The air research board works nearly hand in hand with the EPA and EPA is federal.


so those numbers mean something.

Nowanker

True, they have zero authority elsewhere...
But other states and the EPA do use CARB acceptance as a standard for emissions legality.
Thought I left the DPRK behind, but its presence is felt far and wide.

Spaceme1117

The stock Z06 manifold flow very well. I would only upgrade to a long tube header if you were going for big power.

If you were to get headers, I would stay away from ARH. Too many fitment issues. Kooks with the green cats would be the way to go.

Z.06

For me, I am not interested in big power bragging rites, so my answer has been to keep the stock exhaust manifolds with a muffler mod (done correctly), mild camshaft, and ported OEM intake manifold. All of this has been aimed at keeping a broad torque curve. Heads are fully fixed but w/o aftermarket porting which may diminish midrange torque. My short block was built by LME in Houston with Callies Compstar forged steel crankshaft and rods and Wiseco forged pistons. Camshaft is Cammotion Titan 1. Main use of the car is to and from the track, and on the track for HPDE events.