[oldman]

Originally Posted by Atomic Ed

I'm thinking the same thing Oldman. Considering shorties and a primary cat delete since I see no real advantage on the ZL1 exhaust system

Do you think moving the secondary O2 sensors to behind the secondary cats will work? Not sure if the freer flowing secondary cats will suffice to keep the secondary O2 sensors happy.

To my mind the only potential problem is the second cats especially with larger more surface area Hooker shorties will take 30 seconds longer to light-off and there is a potential in cold weather and light throttle driving after start up to trigger a cat inefficiency light. This is a common problem with most new cars that have a pup cat / primary cat system that is replaced with a larger free flowing exhaust. The problem is self correcting but people freak out anytime the get a check engine light.

I would have gone with ST and front cat deletes myself but I felt that LT would help in the mid range as I have a MSD and a M6. I intend to do cam and heads one day.

For an auto, or for somebody with no intention to move to cam / heads. I would be that ported stock IM, ported TB, aftermarket or slightly cleaned up factory headers and primary cat deletes would be the way to go. Especially now that we know even GM has pronounced the stock system good to 650 HP. Lingenfelter does NOT change the headers and exhaust with their "base" package(s). I use the term loosely as Ligenfelters base goes from mild to crazy. Aslo factory header is similar to the Z/28 at 505 HP and I believe the hot LT1's 535 rating is based on factory header if not the whole factory exhaust.

For the primary cat deletes. You do lose the front hanger that bolts to the front cat. I would fab a new set of hangers as that is a BIG exhaust and there is introduction of false knock. I would probably install a stainless steel flex pipe in one of the front cat deletes (only in one leg probably driver's side). This will break up any resonance / oscillation in the exhaust.