CurtDrums

Hello. I'm new to this forum and looking for some solid advice. I'm on A budget--most of us are right, and I need to pull the cats out because they have become defective. I'm going to install an SLP cold air intake, remove the cats, and run a magnaflow muffler, then have the car retuned at a Dyno Speed shop. For the expense that a good set of LT headers cost, will they significantly increase HP and low end torque gains over using the stock manifolds? What can I expect to gain if I stay with the stock manifolds and what would it increase by using LT headers? Finally, if you guys think headers are a must, which headers are well matched for my car? If I go with headers, I would want them to have a smooth power curve for daily driving. I don't plan to do anything else to it (cam, heads etc). This is a one time project. Thanks in advance for weighing in!

Fatdog2

Whatcha got?What year?Auto or 6 speed?What state?

CurtDrums

My car is a 2000 z28, automatic, drop top, 65000 miles

CurtDrums

Oh, and appears to be bone stock.

cheapchevy

My first mod was Flowmaster muffler. Sounded faster. Second mod was SLP shorty headers. This time I could feel car was stronger both at bottom and top ends. If you don't have to worry about smog and are going to run without cats, then you will get more power from long tube headers. I'm also running SLP intake. You will notice good gains from a cold air intake, headers, exhaust, and a tune.

Injuneer

I missed the fact that this exhaust question was posted in "Suspension, Chassis and Brakes". Let's move it where it belongs.

Keep in mind, there are a few differences between the LS1 manifold/Y-pipe/cats and those on the LT1 engine, so comparisons may not be meaningful.

Injuneer

You don't want to replace only the muffler. There is only meaningful power gain if you do a complete catback.... the intermediate pipe, cross-flow muffler (or a resonator tube = Loudmouth) and pipes/tips. You want a 3", mandrel-bent IM pipe to realize good gains. That where the HP is.

As far as deleting the cats, appears you are in Tennessee, so I suspect you may not have a visual or tailpipe emissions check. Really not a lot to be gained by deleting the cats, they might cost you 2 to 3 HP. And the tailpipes of your car will smell without them. You will also need to have the after-cat O2 sensors "tuned out" of the PCM, or you will have trouble codes and an SES light. O2 "sims" are also an alternative.

Chris Endres' "Chevy LS1/LS6 Performance" book indicates up to a 15 rwHP gain with long tubes. Probably less with shorties or mid-length. He recommends for a daily driver, mostly stock setup you stick with the shorties or mids. For all-out, max HP applications, the long tubes are a good idea. Be sure to consider a cera-metallic coating on the headers to reduce underhood temperatures, reduce header rusting and thermal stress cracking, and maybe pick up a couple extra HP with higher primarily velocities an increased scavenging.

I'm not an LS1 expert, so maybe an actual LS1 owner can add to or correct the above.