boonie c4

I want to install a exhaust header system for my 012 G.S. LS3 Corvette. Does anybody make a carb legal header system for California? I notice that there are some forum members from California with headers installed in their Corvettes how do they get away with it? whats their secret?

Mike's LS3

No, headers are illegal in CA. CA emissions do not like the idea of moving the cats downstream at all.

Full Z06 or ZR1 exhaust is our best option.

Peterk760

so Mike, I have a base LS3 and was wondering about headers too...
What would a full ZO6 or ZR1 exhaust bring to the table over a base LS3 exhaust?
TIA, Peter

Dano523

Z06 OEM exhaust manifolds are shorty headers with collectors, so a gain of about 12HP.




With long tube headers, you get better scavenging due to the longer tubes, so you pick up about 25hp instead.


So since CA does not have CARB# legal headers (short or long tube), by running the OEM z06 manifold, cats, and X pipe, it's very hard for a novice smog guy to pick up that the oem GM Z06 exhaust parts are not correct for the car model, and does not snag you on having none OEM parts on the car for that model during the smog visual check.

Mike's LS3

I have a boosted 2008 manual with no other engine mods, except for the Z06 exhaust. I have an A&A CARB certified kit. As Dano mentioned, the exhaust is all Z06 original GM part #s with no modified welds done to them, so I pass the visual inspection.

After the CA mandatory emissions recall, my car was not happy with the 4 cat system, especially being boosted. So, I swapped the LS3 NPP exhaust with 4 cats to a full Z06 exhaust (2 cats) and retuned.

On the same dyno with same tuner I gained 28 rwhp and 23 ft. lb. torque. The power increase was throughout the entire rpm.

Swapping from a stock LS3 with NPP to Full Z06 exhaust or even keeping the NPP mufflers and a good tune, expect around 22-27 more rwhp and torque.

Just as a side note:

The Z06/ZR1 exhaust manifolds have hydroformed stainless steel tubes within stainless steel jackets. These tubes are mig welded on the inlet and actually float inside the jacket allowing the expansion and contraction through heat cycles which play an important part in longevity. Notice the space between the tubes and collector's mouth. The shape of the tubes are designed to keep restriction to a minimum. GM did their homework.

AORoads

Mike, I don't know about the HP gain, but isn't the Z06 full system a slightly different, full NPP, too? I mean IIRC the Z was the first one to get the NPP exhaust in '07. I could be wrong. I do know that the diameter is different, 3" for Z, 2.5" for LS2/3.

Edit: Z06 first had "NPP-style" exhaust in model year 2006 (from HOXXOH post below)

Mike's LS3

Both very similar systems with design changes over the years.

In 2007, the Z06 3" "dual mode" exhaust had an "H" pipe with perforated by-pass pipe in the muffler along with non perforated exhaust tips.

In 2008, the LS3 had the NPP 2 1/2" with an "X" pipe and a solid by-pass pipe in the muffler along with perforated exhaust tips.

In 2011, Z06 had an "X" pipe with a solid by-pass pipe in the muffler along with perforated exhaust tips. Basically, GM used the ZR1 exhaust for the Z06. This made for a louder exhaust at WOT.

In 2012, GM added two smaller cats at the mid pipe for a 4 cat system to all corvettes.

HOXXOH

To add to the above, the Z06 was the first to use the dual-mode mufflers in 2006 and they were/are not coded NPP, since it wasn't an option.

Dano523

About right, since your going to pick up about 12'ish HP from the Z06 oem shorty headers, and the rest will be the return over the stock OEM tune instead. So 12'ish HP from the manifolds, and about 16'ish HP from the re-tune over the stock oem tune alone instead.

If you don't have NPP mufflers now and add them in as part of the system, then you can tack on about 6more HP for the NPP mufflers as well.