MagnaFlow 16636 Cat-Back Install on a 2004-2005 CTS V 5.7L
By MagnaFlow Exhaust, Mufflers & Cat Converters - Quality | Published: 2026-11-01
Category: Product Reviews
A step-by-step install guide for the MagnaFlow 16636 Street Series cat-back on the 2004-2005 Cadillac CTS V 5.7L, with checkpoints for fitment and sound.
Quick answer
Install the MagnaFlow 16636 cat-back on your 2004-2005 CTS V by dropping the stock system first, test-fitting the new pipes loosely, then tightening from front to rear. Check rear tip alignment and hanger clearance before you start the engine.
Why the 16636 suits the LS6 CTS V
The 16636 is a Street Series system with 2.5-inch mandrel-bent main piping and two straight-through mufflers, ending in a dual split rear exit with 4-inch polished tips. That combination gives the 5.7L LS6 a deeper, more resonant tone than stock without the drone some louder systems introduce on long drives.
It is a direct-fit cat-back for the 2004-2005 CTS V, so you are replacing the factory rear section rather than building a custom system. If you want a quieter cabin or a more aggressive note, the 16636 sits in the middle of MagnaFlow's range; compare sound goals before buying.
What the kit does not tell you
MagnaFlow's catalog facts for the 16636 list piping size, muffler type, exit layout, and tip style, but they do not publish installation torque values or a step-by-step procedure. Use the factory service manual for torque specs and treat the steps below as a fitment and sequencing guide.
The catalog also does not list optional tip finishes or valved variants for this part number. If you need a different tip style or an active exhaust valve, confirm availability before ordering rather than assuming the 16636 covers it.
Install steps for the 16636 on a 2004-2005 CTS V
- Lift the car and support it safely: Raise the CTS V on jack stands or a lift so you can work under the rear section. Common mistake: supporting the car under the exhaust or fuel lines instead of the factory jack points. Confirm the car is stable before you loosen any exhaust hardware.
- Disconnect the battery and let the exhaust cool: Wait until the stock system is cool to the touch, then disconnect the negative terminal if you will be near wiring or the rear bumper. Checkpoint: never work on a hot exhaust.
- Remove the stock cat-back: Unbolt the factory system at the flange ahead of the rear section and release the rubber hangers. Common mistake: cutting pipes you may need to reuse for mock-up; remove the stock system intact first. Keep the factory hangers and hardware until the new system is fully hung.
- Test-fit the 16636 loosely: Hang the new pipes and mufflers on the factory hangers and start the flange bolts by hand. Do not tighten anything yet. Checkpoint: the 2.5-inch piping should clear the floor pan and rear suspension through full suspension travel. If a pipe contacts the body or axle, loosen and re-clock the joint before tightening.
- Align the dual split rear exit and tips: Center the two 4-inch tips in the rear bumper openings, matching height and depth side to side. Common mistake: tightening the rear sections first, which pulls the tips off-center. Because the tips are welded on, final tip position comes from pipe rotation, not tip adjustment.
- Tighten from front to rear: Snug the flange connection first, then the muffler and tailpipe joints, then the hanger clamps. Use the factory service manual for torque values. Checkpoint: recheck tip alignment after each joint is tightened. A second pass on all clamps after the first heat cycle prevents leaks and movement.
- Start the engine and check for leaks: Reconnect the battery, start the engine, and listen for ticking or hissing at each joint. Common mistake: skipping the leak check because the sound seems fine at idle. If you hear a leak, loosen the nearest joint, reseat the pipe, and retighten.
Product facts
- MagnaFlow 2004-2005 Cadillac CTS V 5.7L Street Series Cat-Back Performance Exhaust System 16636: 2.5-inch mandrel-bent main piping with two straight-through mufflers and a dual split rear exit. Mandrel bends keep the pipe diameter consistent, which supports flow on the 5.7L LS6 without changing the direct-fit layout.
MagnaFlow 2004-2005 Cadillac CTS V 5.7L Street Series Cat-Back Performance Exhaust System 16636 - MagnaFlow 2004-2005 Cadillac CTS V 5.7L Street Series Cat-Back Performance Exhaust System 16636: 4-inch polished welded-on double-wall angle-cut folded-edge tips. The tips are fixed to the tailpipes, so rear alignment is set by how you clock and tighten the system, not by adjusting the tips separately.
