I have a 2005 LS2 MN6 coupe which is totally stock except for Borla axle back mufflers and an A&A Vortech V-3 Si supercharger intercooled kit installed (60# injectors, NGK plugs, MSD wires and BAP). Right now i'm making 552rwhp and 476lbft torque. I'm having some custom rear wheels made so I can mount Nitto NT555 RII in 305/35-18 track tires and put more power to the ground. My speed shop is telling me the next upgrade should be headers, but I've talked to two other people that said headers didn't add any power on their supercharged set-up, one was running a V3Si on a LS2 like me and the other Magnuson supercharger on a LS3. I don't want to spend $1500-$2000 on headers if the net gain I sent at least 30+HP. For that kind of money I'd rather spend a bit more and have a can installed. I'd like to hear about your experience if you are an actual Vette owner. If you work at a speed shop and have an opinion, you can tell me your experience but please identify the shop you work at. As always, your help is greatly appreciated.

 

Yes, headers will add power. It's not going to be huge, but I'd expect gains of 25 rwhp and probably more torque. The nice thing is that the gains are pretty much always throughout the entire rev range.

In my opinion, headers are more about building a solid foundation for making power vs. actually adding big power. If you're considering a cam or smaller blower pulley, then headers absolutely make sense. The more power the engine is capable of making, the more the stock manifolds/cats will be a bottleneck.

The stock LS2/LS3 cats are also known to fail very easily with added power. Adding headers takes care of that. The high-flow cats that come with most headers will hold up better in the long run.

 

I'd guess you might see 30+ hp on a supercharged car. Keep your eye out in the classifieds, I bought a brand new set of B&B's that someone bought but never installed for 1/2 of what they cost new.

 

Thanks for the input. Looks like headers are in my future. The speed shop also recommended to go with a smaller blower pulley so that's my next plan of action after the new tires and wheels. My goal is to drop into the high 10s and then I'm good for a while.

 

Sorry for the slight hijack. I picked up some headers to complete my corsa exhaust, how many people keep the rear 02's than just plugging them? A local shop wants $200 to hook up car and delete cel if I were to eliminate rear 02's. I would rather wait until cam/springs to take it to the shop and do a full tune for a few hundred more. Seems like extensions is considerably cheaper than the $200 for a cel removal.

 

Totally stock except for some mufflers and, oh yeah, a SUPERCHARGER, LOL. Talk about burying the lede. It's like a chick saying, "I'm all natural, no plastic surgery, oh, except for this TRIPLE EEE BOOB JOB."

IMO, headers are way too much money for your situation in terms of bang-for-buck. Drop a pulley size and add meth for that price and you'll add 75HP easily (ask A&A Andy or Josh if they concur). I went from 595 to 666 just adding meth and a more aggressive tune.

A blower cam is nice too, but you're looking at like $2500+.

Oh, and if you want better exhaust flow, pick up some used LS7 manis, catpipes, and midpipe, and you are 1/2 way to headers. I've seen them on here for as cheap as $250.

I'm at 666 RWHP with Si, 3.6" pulley, meth, and the Z06 mani/cat/midpipes into LS3 NPPs. No cam, no headers. Maybe if I could find some used short tubes to bolt on to my LS7 downpipes, I might go for it, but it would have to be a really good deal.

I'd say headers are a very questionable upsell in this situation. For $2K, you are close to a Ti head unit upgrade with the Si trade in!

 

I bet at you power level stock exhaust is starting to become a bottle neck. I wouldnt be surprised if you saw 40+ with a good exhaust system.

$2k assuming he is buying new high dollar headers. I guess I am in the minority, but I would never pay that kind of money for something that I can pay half or less for "gently used". It might take some time and patience, but I paid $550 for a "newsed" set of B&B headers. A guy bought them, but never installed them.

Just keep an eye out for a couple of weeks, they come up fairly often.

Just my .02

 

You'll get a CEL regardless of what you do -- unless the rear 02 codes are turned off. The high-flow cats are too far from the engine and usually not efficient enough to keep catalyst codes from popping up.

I ran extensions on my last build, but this time I decided to plug the holes. There really isn't any valid reason I can think of for keeping the rear 02s with headers. It's a much cleaner and easier install without them, and your tuner will turn the codes off either way.

About the only reason I could think of for keeping them would be if you have a state inspection that requires them to be there.

 

The Z06 manifolds and cats are a good option if you want to stay stealth and more or less smog-legal, but they lose power to a good set of headers. I found a set of super low mileage ZR1 take-off parts and ran them a while after I got tired of dealing with my crap LG headers. In the end, I ended up going back to headers for the power.

The other concern is durability running factory cats. The stock LS3 cats don't hold up to FI. The LS9/ZR1 cats I have (different part numbers and more $$$ than Z06 cats) are about as good as you'll find, but mine were starting to show signs of failure after less than a year of use at around 700 whp.

I never did any back to back testing when going from the ZR1 setup to the Pfadt headers, but there was a noticeable increase in torque. They also reduced the amount of knock retard I'd see while tuning -- allowing more timing vs. the ZR1 parts. Even with meth, we need all the help we can get with our 91 octane.

 

A new, smaller pulley on a centri costs $125 and yields an extra 2# of boost. Compared to $1500-2000 for headers? Headers might be good for NA, but for FI, it's not even close. As I said, just adding a meth kit picked me up 71 HP, double what you would get from headers. At his HP he could do meth and a pulley drop and go up 100HP, around triple headers' gains for the same price.

If money (and visual smog checks) are no object, sure, why not. But bang for buck?

 

If he wants to pulley down and add meth, then sure, that's an option. But headers are win-win when planning an engine combo. More power with less boost = a good thing. Even with meth, you get to a point where you're octane-limited. Start tuning your own car and you'll see this.

On top of that, the stock LS2/LS3 cats are a liability -- and the OP has them. I would not pulley down with those things in place. He could gut them, but some guys (myself included) don't like running catless.

Much like used LS7 exhausts, used headers are out there for guys that don't want to spend that type of money.

 

How are/were you determining that your cats were failing?

 

When I took them off to go with the newly released Pfadt headers, I found cracks and some missing cells in one of the cats. I've seen lots of destroyed cats over the years, and it looked liked early signs of failure to me. They were perfect when I installed them 8 or 9 months earlier.

I had a strong feeling I'd have issues like that at my power level, but I still wanted to try them out. I specifically bought the ZR1 cats, with the thinking that they might prove to be more robust. While they look identical on the outside to the LS7 parts, they are quite a bit more expensive and carry a different part number.

I'd read about a number of ZR1 owners having cat failure, but they were mostly hardcore track day guys. I hoped I'd be okay with mostly street use and some roll racing. Guess I was wrong. I'm thinking the pulls into 5th gear at the Shift-Sector events are what hurt them.