Hi Guys, just wondering if any of you had any experience in this area. I have the distinct (mis)fortune of living in the People's Republic of California, which makes any kind of performance modification exponentially more challenging, if you want to remain within the letter of the law. Bottom-line, is I want to be able to get my truck smogged indefinitely going forward without headache, which is the main reason for this post.

I currently have an '04 Avalanche with an LM7 5.3L. It's got about 165k miles on it. Runs pretty well all things considered, but looking at an engine swap within the next 12 months or so. The two main options I'm looking at are either an L9H Gen-IV 6.2, and throwing an Edelbrock E-Force blower on it, or starting with an LQ4 short block, and building it up with heads and a blower.

My main question is, how much do aftermarket heads change the flow and sensor parameters, and can heads alone trigger check engine lights? If an engine or supercharger kit is calibrated for OEM, and you throw some performance heads and headers on, is it an almost guaranteed CEL, or is that more determined if you have a lumpy, high-lift cam?

In a perfect world, I'd like to do the L9H with some AFR or Trick Flow CARB-legal heads with the E-Force blower. But the last thing I want is to get everything bolted up and running, just for it to throw CELs or rat me out at the ref station when they plug in the OBD-II scanner in my quest to get the magic sticker. Any professional guidance or advice appreciated. Spare me the "Commie-fornia sucks!" repliles. Thank you Captain Obvious. Believe me, I know.

 

Move to a free state, problem solved.

 

Thanks, Captain Obvious.

 

Since California basically outlaws any modification of OEM emissions equipment that means you have to keep the stock headers and cats. That alone will somewhat the advantage of aftermarket heads and all your mods in general. High overlap cams will also prove troublesome for passing emissions, but the good news is the heads themselves should be pretty transparent emissions wise while offering more performance. Throw better heads on with even a stock cam and it does better. Heads are not an automatic check engine light. Your cam is going to be the main thing that causes headaches.

 

Thanks Atomic! That's the main info I was looking for. I think I'm probably going to stick with the stock cam. But from what I've read, just the heads alone can unlock a fair bit more power. There are several CARB-approved headers out there, and AFAIK, as long as all the obviously non-stock parts under the hood have a visible and current EO number on them, you should be good. Much appreciated.

 

Under the hood I think you will be ok with that, but for the CATS I am pretty sure any modification of exhaust system related components is not allowed, which means you cant move the cats at all including the header in front of it. Basically the only thing you can do is a muffler and air filter

 

@Atomic....JBA has these for the Escalade, which would be the closest equivalent for the engine swap:

JBA Performance Exhaust Part #:1850S-2JS Cat4wardŽ Shorty

Says CARB EO #D-57-33

 

Yea that looks exactly like the factory manifold, there wouldn't be any gain with that. Does look better though.

 

Well, if I'm going "by the book" I think it's my only choice.

 

I was afraid of long tubes for a long time so I only ran shorty headers. I did notice a small power increase on almost every engine. And installation was always easier than long tubes. And I noticed less valve noise with short tubes. Glass half full and all that. Cali might limit your options but you still have options. However, if you are going forced air, cam, heads, and exhaust are a lot less important. FI will for the most part ignore the restrictive stock equipment. I would buy the SC first and then decide if you need more.