[IH8WNTR]

I’m curious as to what kind of gains people are seeing while keeping a full stock exhaust including secondary cats. Would a stock exhaust hurt anything other than leaving power on the table?

[6spdhyperblue]

No full stock exhaust is fine. If you go supercharged at the limit of the bottom end you will lower exhaust gas temp but that’s north of 650rwhp. I think someone ran 10s on stock exhaust with bolt ons. So go msd intake manifold and 95mm throttle body, cai, ati pulley, e85

You should be at 450rwhp. Carb compliant

[pyroguy]

It shouldn't hurt anything when you're modded to the point of needing a tune when you have a proper tune on the car. However, like you said you'll be leaving power on the table leaving factory cats on the car.

[IH8WNTR]

Would going as far as doing a custom cam and ported heads be ok too? I’m ok with not being the fastest or make the most power. I just want to not have to worry about the smog laws and making the exhaust louder. The track I’m closest to has a noise limit and I slip just under in stock form.

[6spdhyperblue]

Yeah just get a custom cam and tell them about the exhaust. I’ve done this exact thing before. The custom cam is barely more than the off the shelf

[wnta1ss]

You can get decent SS bolt-on performance with the stock exhaust, however, you will indeed be giving up some power compared to someone with long tubes and modded exhaust. As far as problems, probably not an issue; I have run a base supercharger on mine, and also a bolt-on configuration, both with the all-stock exhaust, and did not see any problem.

The comment on someone running 10s with bolt ons and stock exhaust is true. First person that I know of to accomplish this was Snowblind, who ran 10.98 sec in his SS using that configuration. Then at a later date, I ran 10.88 sec with mine in this configuration.

[KingLT1]

Stock exhaust from the factory tri-y to the suitcase has been 9.9 @ 140 on Magnuson's shop car.

[asrautox]

I'm in CA so this is my path too. The secondary cars aren't monitored, so you can technically pass smog without them, but you will no longer be noise legal at your local track. You can also do Hooker shorty headers for a slight gain over the stock manifolds (~8whp iirc), which are also CARB legal and wont affect your exhaust noise..

[IH8WNTR]

Thanks for all the responses. Looks like I’ve still got a lot to play with and still go plenty faster.

[oldman]

If and when I sell my ride for say a C8, I would put the stock headers back on, front cat deletes, stock the rest of the way back. The engine would be fully forged, ported heads, pretty big cam, ported intake, ported TB, CAI. I think I would be leaving say 25 HP on the table compared to LT, high flow cats, and 3" all the way back... No "big" deal if you ask me. I've run full boltons including E85, stock headers, front cat delete and a tune for a bit and was COMPLETELY happy. It really was NOT a nigh and day difference going LT, high flow cat, second cat eliminated....

[avalonandl]

If i get heads/cam I intend to keep the stock exhaust system. Don't wan't headers.

[Osbornsm]

Originally Posted by avalonandl

Don't wan't headers.

But whyyyy tho ???

[oldman]

nothing wrong with the factory headers, I would do the front cat deletes. I thought it was well worth it.

[KingLT1]

Originally Posted by Osbornsm

But whyyyy tho ???

Because the added noise and rasp isn't worth it for the modest power gain imo. Delete the primary cats where 80% of the restriction is, keep the secondary's which restrict little to nothing, and you end up with a nice sounding exhaust that isn't too loud. On a 650whp blower car, Long tube headers only gained 19hp compared to stock tri-y with cat deletes. It would be even less on a NA car. This isn't 2002 where headers and full exhaust nets 40whp gain.

It would be nice if a company would pickup where CA performance left off and started manufacturing the bolt-in primary cat delete pipes again.