Which exhaust manifolds?

[EVOeng]

Hi All,

Its been a few months since I last posted about my search for a Z28. I ended up buying a car within a week of my search starting and I've loved driving/owning it.

I'm now thinking about replacing the exhaust manifolds/headers and sport cats. What are owners opinions on which brand to go for? Which diameter is recommended for an unmodified engine (I've just got the AHP heads)? Does anybody have a diagram/drawing of the Z28 exhaust layout? Do the factory manifolds have pre-cats in addition to the main cats?

Thanks in advance!

[DasBaldDog]

I have the ARH 1 7/8 headers (short system, just headers with catless extensions).

I THINK the only other company that makes Z/28 specific headers are Kooks (note that Kooks sells their header extensions seperately and I think you have to use their extensions if connecting to factory H pipe).

There is some rumors that the regular Z06 headers fit (and are cheaper even for the same brand) but ARH says that they have the same start/stop points, there is supposedly significant clearancing to avoid the oil cooler, other stuff that is different between the Z06 and Z/28. I could not find any evidence of someone actually USING the Z06 headers.

I think general understanding is that the 1 7/8 will work great for stock engine but that the second you port heads, go big cam and/or port/swap intake manifolds then the 2 inches are probably wise.

There are some good pictures linked in this thread of the entire exhaust as it is under the car.

https://www.camaro5.com/forums/showthread.php?t=572740

[HoodCheck]

Yep Kooks and ARH are the only 2 companies afaik. If no plans to upgrade to boost (which requires its own set of upgrades), then 1 7/8" should work fine. I had 1 7/8" on mine w/ the green cats and it was stupid loud. Unfortunately, I bought the version with green cats due to being, supposedly, 49 state emissions legal, and to avoid the smell of gas. They do not, AT ALL, avoid the strong gas odor. I actually planned to go back to stock, but ended up trading it in (although I plan on trading this '17 ZL1 I got back in for another Z/28).
Honestly, I'd recommend staying stock, but that's just me. If I had it to do over again (which I will soon), I wouldn't have done a single mod.

[PapaKlutch]

Originally Posted by EVOeng

Hi All,

Its been a few months since I last posted about my search for a Z28. I ended up buying a car within a week of my search starting and I've loved driving/owning it.

I'm now thinking about replacing the exhaust manifolds/headers and sport cats. What are owners opinions on which brand to go for? Which diameter is recommended for an unmodified engine (I've just got the AHP heads)? Does anybody have a diagram/drawing of the Z28 exhaust layout? Do the factory manifolds have pre-cats in addition to the main cats?

Thanks in advance!

The Z has 2 cats per side and 4 cats total; a Primary and Secondary on each side. Photo of the Z/28 underbody for a good look at the exhaust system.

American Racing Headers long tube headers with 2-inch primaries to one high flow cat per side to their X-pipe to the factory dual-mode exhaust is a common upgrade. Photo of the ARH long system attached...

[Yessa]

One idea is to remove the stock Manifolds and have them cleaned and widened for better exhaust flow. A lot cheaper than Headers.

[EVOeng]

Thanks for the replies.

HoodCheck, what's the difference between the normal cats and Green cats?

PapaKlutch, thanks for the image, am I right in assuming the primary and secondary cat is on a single piece (separate to the exhaust manifold)? Are there two or three lambda sensors on each side?

From looking at Kooks and ARH websites, I cannot just replace the connecting pipes with sport cats, instead I need to replace the manifolds and cats?

[DasBaldDog]

Originally Posted by EVOeng

Thanks for the replies.

HoodCheck, what's the difference between the normal cats and Green cats?

PapaKlutch, thanks for the image, am I right in assuming the primary and secondary cat is on a single piece (separate to the exhaust manifold)? Are there two or three lambda sensors on each side?

From looking at Kooks and ARH websites, I cannot just replace the connecting pipes with sport cats, instead I need to replace the manifolds and cats?

On the stock exhaust, both cats (per side) are on a single section of tubing which can be disconnected from the manifolds themselves, you are correct.

There are two sensors per side.

Can't help you with the other questions, sorry.

[HoodCheck]

Originally Posted by EVOeng

Thanks for the replies.

HoodCheck, what's the difference between the normal cats and Green cats?

PapaKlutch, thanks for the image, am I right in assuming the primary and secondary cat is on a single piece (separate to the exhaust manifold)? Are there two or three lambda sensors on each side?

From looking at Kooks and ARH websites, I cannot just replace the connecting pipes with sport cats, instead I need to replace the manifolds and cats?

The green cats have the O2 sensor in the proper location, supposedly allowing for no-tune installation without throwing a CEL, plus being 49 state street legal. That is of course keeping in mind that LTs are likely to get an auto fail for any visual inspection anyways...gotta have a shop to ignore that aspect in those areas

The hi-flow cats supposedly have more of a smell to them (bad enough to me with the green cats), and will need tuned. Supposedly the green cats actually flow better, however, they also cost 500-700 more for that set.

[Ls_Camaro]

Originally Posted by HoodCheck

Yep Kooks and ARH are the only 2 companies afaik. If no plans to upgrade to boost (which requires its own set of upgrades), then 1 7/8" should work fine. I had 1 7/8" on mine w/ the green cats and it was stupid loud. Unfortunately, I bought the version with green cats due to being, supposedly, 49 state emissions legal, and to avoid the smell of gas. They do not, AT ALL, avoid the strong gas odor. I actually planned to go back to stock, but ended up trading it in (although I plan on trading this '17 ZL1 I got back in for another Z/28).
Honestly, I'd recommend staying stock, but that's just me. If I had it to do over again (which I will soon), I wouldn't have done a single mod.

Just to hear your wanting to trade in your 17 ZL1 for another Z28 just tells me how special that car really is. Maybe it’s because you like the rawness of the Z28 versus the refinement of the newer generation ZL1.

[HoodCheck]

Originally Posted by Ls_Camaro

Just to hear your wanting to trade in your 17 ZL1 for another Z28 just tells me how special that car really is. Maybe it’s because you like the rawness of the Z28 versus the refinement of the newer generation ZL1.

I consider it my favorite car ever owned, and that's saying something for someone who gets 1-2 different cars per year.
Initially the LT4 impressed me for about a day, not even...maybe 50 miles before I wanted my Z/28 back. I'm actually more impressed with the A10, its a badass transmission really.
The 6th gen has the ZLE, which has the newer DSSV and from what I hear, a more raw ride than the Z/28, but I find it dogshit ugly. To me the only bigger mistake I ever made than trading in my Z/28 was getting married, twice lol.

But in all honesty, initially I thought the LT4 might offset my distaste for the looks and cramped space and interior. I could care less about the tech or other things in it that I'll never use (heated/cooled seats and things like that). I upgraded the stereo to a touchscreen in my Z/28 so I could get android auto and a screen for a reverse camera, thats all she needed.
I was mistaken though, it didn't offset it, and I'm not a fan of the looks or interior of the car honestly. In my case, just an all around mistake, and I can't wait to get a Z/28 back into the garage. To be fair though, I always thought the Z/28 was too slow, but I still liked it much better.

[PapaKlutch]

Originally Posted by EVOeng

Thanks for the replies.

HoodCheck, what's the difference between the normal cats and Green cats?

PapaKlutch, thanks for the image, am I right in assuming the primary and secondary cat is on a single piece (separate to the exhaust manifold)? Are there two or three lambda sensors on each side?

From looking at Kooks and ARH websites, I cannot just replace the connecting pipes with sport cats, instead I need to replace the manifolds and cats?

The LS3 and L99 Camaros do have aftermarket hi-flow cat pipes (Solo Performance is one company) aka sport cats available for placement between the OEM exhaust manifolds and the H-pipe. I do not know of any ready-made hi-flow cat pipes for the Z/28.

[joelster]

The restriction in the factory exhaust is the cats, not the manifold itself. I just installed 2" Kooks long tubes and catless mid pipes last night. I'll do a write up once these pics upload.

[Ls_Camaro]

Originally Posted by HoodCheck

I consider it my favorite car ever owned, and that's saying something for someone who gets 1-2 different cars per year.
Initially the LT4 impressed me for about a day, not even...maybe 50 miles before I wanted my Z/28 back. I'm actually more impressed with the A10, its a badass transmission really.
The 6th gen has the ZLE, which has the newer DSSV and from what I hear, a more raw ride than the Z/28, but I find it dogshit ugly. To me the only bigger mistake I ever made than trading in my Z/28 was getting married, twice lol.

But in all honesty, initially I thought the LT4 might offset my distaste for the looks and cramped space and interior. I could care less about the tech or other things in it that I'll never use (heated/cooled seats and things like that). I upgraded the stereo to a touchscreen in my Z/28 so I could get android auto and a screen for a reverse camera, thats all she needed.
I was mistaken though, it didn't offset it, and I'm not a fan of the looks or interior of the car honestly. In my case, just an all around mistake, and I can't wait to get a Z/28 back into the garage. To be fair though, I always thought the Z/28 was too slow, but I still liked it much better.

Well the Z28 is definitely your ride or die my friend.

[Yessa]

Originally Posted by joelster

The restriction in the factory exhaust is the cats, not the manifold itself. I just installed 2" Kooks long tubes and catless mid pipes last night. I'll do a write up once these pics upload.

Gasoline smell is unbearable?