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Hi there! I've got a 4spd auto z28 and I love kt. But it's too quiet. I live in California and with the new exhaust fine crap going on I know I shouldn't waste money on "modifying" my exhaust... But what if I could track down some "factory" SS SLP exhaust parts, like the LM2 and maybe a 2002 SLP airbox lid? Would this make my z28 sound better? Right now it's got the stock square pipes. I'm a noob to modifying cars. Thanks in advance for any input!
The lid would probably get you 12 RWHP or so, and a "Loud Mouth 2" would definitely make your car louder. If you can do that and get away with it in that... state... I would go for it.
The LM2 was not a "factory" SLP offering on any SS car, so this would not be considered stock. The only SLP exhaust upgrade which was available to be ordered on a new SS for your model year was the "dual/dual" system (which uses a traditional crossflow muffler in the factory location rather than the I-pipe mounted bullet muffer of LM1/2).
The SLP dual/dual system offers extremely good flow (as good as any aftermarket catback) but only a slight increase in noise. It pairs well with an ORY/LT headers because it generally keeps rasp away. With factory cats and manifolds, it will in fact be a bit louder than your current base system but only marginally so. However, it's a nice improvement in flow over the base V8 system (in addition to the muffler upgrade, it also replaces the 2.75" factory I-pipe with a true 3" unit.)
If you are limited to using only "factory/OEM" parts, then the dual/dual system would be the only upgrade available for your application. They haven't made these new in many years, so you'd have to find a used system.
Thanks for the information! Looks like I'll be trying to track down that dual dual system! I really am not a fan of the four tips... Watch me change the tips and then get knocked for modifying the exhaust anyway.
The horse power gain sounds appealing too. Would I have to get the car re tuned after I install the intake and exhaust?
Thanks for the information! Looks like I'll be trying to track down that dual dual system! I really am not a fan of the four tips... Watch me change the tips and then get knocked for modifying the exhaust anyway.
I can't imagine you'd fail for a tip change, but you could always swap over the square black Z28 tips if you prefer those, or the high polished single-outlet dual tips from the base SS system - either of those are technically stock.
Originally Posted by walker why
The horse power gain sounds appealing too. Would I have to get the car re tuned after I install the intake and exhaust?
No retune is needed for an air lid and catback swap (nor was there any special factory tuning for this equipment on examples originally optioned with these upgrades in the first place). You can usually expect a gain of about 7-10rwhp for each item on an otherwise completely stock car.
On a side note about the air lid, if you are looking for the *original/OEM* optional upgrade lid from SLP (also known as Blackwing) for a 2002 SS optioned with the "345hp package" (or a 2002 Firehawk), be prepared for some very high prices on this used item (as compared to the price of a brand new aftermarket upgrade lid).
Doesn't sound like there's really anything new to worry about in CA then. Many states have laws like this about excessive exhaust noise, the only real difference seems to be the structure of the penalties and/or corrective actions required.
But there's nothing shitty about the SLP dual/dual system. It flows as good as any aftermarket catback (as proven by many dyno tests) and pairs well with an ORY as it produces minimal rasp. It really was a great "factory" system and was also sold as an aftermarket piece for many years. On the subjective side, most folks find it to be too quiet when used with factory manifolds and cats (this was my feeling as well, but it did sound pretty good with headers/ORY/cam) but, objectively, it's a very good flowing catback (especially for how quiet it is).
Yeah, but it's not available anymore and many better systems are. And a loudmouth is the most horrendous sounding exhaust known to man.
Correct, it hasn't been available to purchase new in many years and I wouldn't personally want to go hunting for a used one at this point either, unless it was NOS/NIB - which isn't likely at this point. But dual/dual didn't sound anything like the LM1/2 systems, not even close (only similarity is the dual/dual tips, which the OP doesn't seem to like).
Regarding 3" catbacks, there are certainly other great systems which are still available that are probably about equal in terms of flow, but not likely to be decisively better; SLP dual/dual and 2OTL both have historically shown only marginal losses over a cutout for most applications. They are actually premium systems in terms of flow/power gains.
I'm learning alot here, thank you guys. I have been looking around the internet and it looks like it's going to be tough to find a second hand dual dual. I like that idea of putting my square tips on that system. It's too bad cut outs are so illegal in Cali lol.
As far as the 2002 black wing lid, are the aftermarket lids sold by SLP the same in terms of function? What's special about the actual original ones VS me buying an after market CARB legal air intake?
I'm really glad I won't need to re tune it. Thanks again guys. I'm having a lot of fun with this car and wondering how far down the rabbits hole I'll go 😂... Currently sound deadening the interior, had a water leak and had the strip the whole thing. I watch a lot of car videos but now getting hands on I'm starting to be more open to changing things up on the car.
Black wing was and is a good lid but ridiculously over priced nowadays. The normal SLP lid is pretty much the standard. And it may not fit great, luck of the draw. Mine didn't and I had to play with it for awhile. But it's pretty much mod number one if you're getting into this.
As far as the 2002 black wing lid, are the aftermarket lids sold by SLP the same in terms of function? What's special about the actual original ones VS me buying an after market CARB legal air intake?
As mentioned above, there's no functional difference between the OE-SLP/Blackwing lid vs. the aftermarket SLP lid. They both do the same thing (improve airbox flow and eliminate the air silencer) to increase power, and the gains are basically the same between the two (some have argued that the aftermarket unit flows marginally better due to the neck design, but most dyno tests have shown the Blackwing to be directly comparable in terms of gains). The only real difference is appearance/construction and fitment - the Blackwing unit is built to OEM standards and more comparable in construction material and quality to the base factory/GM lid (hence the demand, and high price, for this used item).
Originally Posted by AnotherWs6
Arent Hooker mid length headers CARB legal?
No mid-length header would be CARB legal for these cars, since a mid-length would still relocate the cats. You can't relocate the cats and stay CARB legal, so mids and LTs are out for any CA inspection. Only a shorty header would retain factory cat location. I seem to recall JBA offering shorty headers for LS1s with a CARB number many years ago, not sure if they still do. Hooker also had a shorty header for a time, IIRC, but I don't remember if they ever went through the process to get a CARB number.
FWIW, the factory exhaust manifolds on the 2000-'02 cars flow just about as good as a shorty header, so any gains would be marginal at best (especially on an otherwise stock engine) and likely not worth the cost and hassle.
^^^^Lol, something tells me russia isnt very concerned with emissions. Hell, they have nuclear subs rotting to pieces all over. Talk about "emissions".
OP, my advise - find a good cat back system. If you keep the factory manifolds and cats I promise you nothing will be too loud.
Throw a lid on it. A powerbond underdrive pulley. Tune it up with MSD plug wires and NGK plugs. ScogginDickey has em as a kit. And if you want something you can really feel change the gears. And converter if you're auto. With sticky tires at a decent track you'll be in the 12's. Especially if it's an auto and you put a stall in it.
If your car is registered in California you will have smog your vehicle every two years. Pending which smog place you choose you most likely will not pass a visual inspection with a cutout. Lids and catbacks are iffy are far as being CARB legal in Cali. I have all the aforementioned SLP Blackwing, dual / dual catback on the car and I've never had an issue when I smog it. JBA shorty headers were the only CARB legal headers in California. Discontinued SLP used parts are not only hard to find but very pricey if you find them in great shape or complete.
RPM WS6 is knowledgeable and knows what he is talking about when it comes to these vehicles.
Hooker has a nice 1 3/4 primary BlackHeart Shorty Header that's CARB approved for 4th Gen LS1's. Hawk's Motorsports carries them.
Sadly, the Mid-length BlackHeart isn't CARB legal. The catalytic converters must remain in the factory location. Mid-length headers typically move the cats. They aren't CARB certified.
Of course some inspection stations may not notice or get excited especially if cats are present.
JBA has 1 5/8 shorty headers are CARB legal in California for 4th Gen's. I would take the Hooker's over the JBA's. There may be some others.
01-27-2019, 05:09 PM
Should I upgrade my 2001 z28 with SLP parts? 
