Why Upgrade Your 5.7 HEMI Headers?

Headers are one of the most effective bolt-on modifications for the 5.7-liter HEMI V8. Factory exhaust manifolds are cast iron, heavy, and restrictive. They force exhaust gases to make sharp turns, creating backpressure that robs power. Aftermarket headers use smoother, larger-diameter tubes to scavenge exhaust more efficiently. The result is a noticeable gain in horsepower and torque, especially in the mid-to-upper RPM range, along with a deeper, more aggressive exhaust note. OEM replacements (for stock restoration or warranty concerns) are also available. This guide covers the complete install process for both OEM and aftermarket headers, including tools, prep, removal, installation, and post-install checks.

Tools and Materials You’ll Need

Having everything ready before you start saves time and frustration. For a 5.7 HEMI header swap, you need:

  • Socket set – 3/8” and 1/2” drive with metric sockets (10mm, 13mm, 15mm, 18mm common). Deep sockets help reach recessed bolts.
  • Wrench set – combination wrenches (metric) for tight spaces. A ratcheting wrench is very helpful on the cylinder head.
  • Torque wrench – a 1/2” drive torque wrench with range up to 80 ft-lbs for header bolts.
  • Header gaskets – MLS (multi-layer steel) gaskets are superior to paper or composite. Buy OEM or high-quality aftermarket (Fel-Pro, Mopar).
  • Exhaust sealant – high-temp RTV or copper gasket maker for collector-to-midpipe connections.
  • Jack and jack stands – a floor jack and at least two sturdy jack stands. Never rely on a jack alone.
  • Safety glasses and gloves – always protect your eyes and hands when working under a vehicle.
  • Penetrating oil – spray bolts a day before to ease removal (PB Blaster or similar).
  • Extension bars and swivel sockets – HEMI exhaust bolts are hard to reach; flexible sockets make a huge difference.
  • Shop towels and wire brush – for cleaning mating surfaces.

Preparation Steps

Vehicle Setup

  1. Park on a level concrete surface. Engage the parking brake and chock the rear wheels.
  2. Disconnect the battery ground cable (negative terminal). This prevents unwanted electrical shorts and accidental airbag deployment.
  3. Raise the front of the vehicle with a jack and place jack stands under the frame rails or pinch welds. Ensure it’s stable before crawling under.
  4. Remove the engine cover (if equipped) by pulling straight up on the plastic trim.
  5. If your HEMI has factory exhaust heat shields over the manifolds, remove them. They may be held by 10mm bolts or push clips.

Check Your Header Type

OEM manifolds use a single bolt pattern. Aftermarket headers often require you to modify or delete the EGR tube (some are not compatible with all states’ emissions). Verify your kit includes gaskets, bolts, and hardware. Some aftermarket headers need O2 sensor extensions or anti-fouler adapters. Measure clearance to the steering shaft and frame – clearance issues are common.

Removing the Old Exhaust Manifolds

Step 1: Disconnect the Exhaust Y-Pipe

Start at the collector flange where the manifold meets the Y-pipe. There are typically two bolts (15mm) holding each side. Spray them with penetrating oil beforehand. Use a breaker bar if they’re stubborn. Separate the flanges; you may need to push the Y-pipe down with a pry bar. If the exhaust is rusted, you might need to cut the bolts – be prepared with a reciprocating saw and new hardware.

Step 2: Remove the Heat Shield and Brackets

On the passenger side, you may have a catalytic converter heat shield that attaches to the manifold support bracket. On the driver side, check for any EGR tube brackets. Remove these to access the manifold bolts.

Step 3: Unbolt the Manifold

Working from the middle outward, carefully loosen each manifold bolt. Use a combination of a ratchet, extension, and swivel socket. Avoid snapping the bolts – they can corrode and break. If a bolt is stuck, work it back and forth with penetrating oil. Once all bolts are removed, gently pry the manifold away from the cylinder head. If it’s stuck (carbon build-up), tap it with a rubber mallet. Carefully lift it out. For the passenger side, you might need to remove the inner fender liner or motor mount bolt for clearance.

Step 4: Clean the Cylinder Head Surface

Inspect the head’s mating surface for any gasket residue, carbon, or damage. Use a wire brush or a plastic scraper to clean it. Do not gouge the aluminum head. Wipe it clean with a shop towel and brake cleaner. If you see deep corrosion or cracks, the head may need resurfacing – consult a professional.

Installing New Headers – OEM or Aftermarket

Step 1: Prepare the Gasket and Hardware

Place the new header gaskets onto the cylinder head studs (if your headers use studs) or position the gasket carefully. Most aftermarket headers use studs that you screw into the head first. Apply a small dab of anti-seize to the stud threads. If your headers use through-bolts, install the gasket between the head and the header.

Step 2: Align the Header

Lower the header into place from above or below, depending on clearance. Many 5.7 HEMI headers install from above on the driver side and from below on the passenger side. Use an extra set of hands or a helper to support the weight. Gently seat the header against the gasket. Do not force it – if it doesn’t slide on, check for obstructions (motor mount, steering shaft, A/C lines). Loosen the motor mount and jack up the engine slightly to gain clearance if needed.

Step 3: Install and Torque Bolts

Hand-tighten all bolts in a crisscross pattern (center outward). Then torque to the manufacturer’s specification. For most OEM-style replacements, torque is 18–22 ft-lbs (check your specific kit). Aftermarket headers often specify 20–25 ft-lbs. Over-torquing can warp flanges or strip threads. A torque wrench is non-negotiable.

Step 4: Reinstall Heat Shields and Brackets

If using OEM manifold heat shields, reinstall them with new hardware. Aftermarket headers may not use shields; you can reuse or discard them. Ensure the EGR tube and O2 sensors are properly routed. You may need to extend O2 sensor wires for aftermarket headers – use solder and heat shrink, not crimp connectors.

Step 5: Connect the Exhaust Y-Pipe

Reattach the Y-pipe flanges to the header collectors. Use new gaskets and stainless steel bolts. Apply a thin layer of exhaust sealant to the joint. Tighten in an alternating pattern to 35–40 ft-lbs (or per Y-pipe spec). Check for leaks by starting the engine and listening for hissing.

Post-Installation Checks

After everything is bolted up:

  • Reconnect the battery ground cable.
  • Start the engine and let it idle. Listen for exhaust leaks at the header-to-head and collector joints. Use a rag over the tailpipe to build backpressure – if you hear a ticking sound, a leak is present.
  • Check for clearance issues: turn the steering wheel lock-to-lock while listening for rubbing. Check wiring, brake lines, and coolant hoses near the headers.
  • Warm the engine fully, then check bolt torque again (retorque after first heat cycle as per header instructions).
  • Lower the vehicle and take it for a short test drive. Monitor for check engine lights (CEL) – aftermarket headers can trigger O2 sensor codes. You may need a tune to disable rear O2 sensors if you removed catalytic converters.

OEM vs. Aftermarket Headers: Detailed Comparison

OEM Headers (Factory Replacement)

Pros:
• Exact fit – no clearance issues, bolt-on with original parts.
• Emissions legal – 50-state legal, retains all cats and O2 sensors.
• Quiet – stock exhaust tone, suitable for daily drivers.
• No tuning required – works with factory ECU.

Cons:
• Performance gain is minimal (maybe 5–10 hp).
• Heavy cast iron retains heat longer.
• No flow improvement over stock.

Aftermarket Headers (Long-Tube or Shorty)

Pros:
• Significant power – 20–30+ hp and 20+ lb-ft torque with proper tuning.
• Better exhaust scavenging, engine revs more freely.
• Lighter weight than iron manifolds (stainless steel or mild steel).
• Customizable – ceramic coating reduces under-hood heat.

Cons:
• Fitment can be tricky – may require grinding, adjusting motor mounts, or removing steering shaft.
• Emissions issues – many long-tubes move O2 sensor position, causing CEL. Cat removal is illegal on road vehicles.
• Needs a tune – to correct air/fuel ratios and disable rear O2 sensors.
• Louder interior cabin drone without proper exhaust system.

Top Aftermarket Header Brands for 5.7 HEMI

Choosing a reputable brand reduces fitment headaches:

  • Borla – high-quality stainless steel headers, often in shorty or long-tube form with excellent fitment.
  • American Racing Headers – known for thick flanges, perfect for max power.
  • Hooker Blackheart – budget-friendly, good power gains, but sometimes require minor modification.
  • Mopar Performance – OEM+ shorty headers that bolt to the factory Y-pipe (good middle ground).

Tips for a Smoother Installation

  • Spray all bolts with penetrating oil the night before. Re-soak an hour before starting.
  • Use high-quality aftermarket gaskets. Cheap paper gaskets burn out quickly.
  • If you’re installing long-tube headers, plan to also install a high-flow catalytic converter and a performance Y-pipe for maximum flow.
  • Have a helper – some header bolts are reachable only from above or below simultaneously.
  • Consider ceramic coating aftermarket headers before installation to reduce engine bay heat.
  • Do not reuse the old header bolts – buy a new Grade 8 or ARP header bolt kit.
  • If the EGR tube interferes, you can block it off with a plate (check local emissions laws).

Common Problems and How to Solve Them

Broken exhaust manifold bolt: HEMI heads have aluminum; steel bolts can corrode and snap. Use a bolt extractor kit or drill and tap carefully. If you’re not confident, take it to a machine shop.

Steering shaft contact: Aftermarket long-tubes often rub the steering shaft. Solution: loosen the steering shaft collar and turn it slightly, or use a mini joint spacer.

O2 sensor codes: Aftermarket headers change O2 sensor placement, causing “bank lean” or “efficiency” codes. Install O2 sensor defoulers (spacers) to pull the sensor out of the exhaust stream, or get a custom tune.

Header bolts coming loose: Torque to spec and use thread locker (medium strength) on header bolts. Retorque after 100 miles.

Should You Tune After Header Installation?

If you install only OEM replacement manifolds, no tune is needed. Aftermarket shorty headers that keep the Y-pipe and upstream O2 sensors in place can often run without a tune, though a tune will optimize the power gain. Long-tube headers require a custom tune (or a flash from a handheld tuner like DiabloSport or HP Tuners) to prevent a check engine light and to set the air/fuel ratio for the increased flow. Tuning also lets you adjust shifts, disable MDS (if desired), and recalibrate the speedometer. Expect to pay $300-$800 for a professional dyno tune or $200 for a mail-order tune.

Conclusion

Installing headers on your 5.7 HEMI is a rewarding project that yields real seat-of-the-pants performance. Whether you choose stock replacements for reliability or aftermarket headers for maximum power, careful preparation, the right tools, and patience are key. Follow the steps in this guide, use quality components, and don’t skip the post-install checks. If you run into fitment issues, forums like RamForum and Charger Forumz offer model-specific advice. With the right setup, you’ll enjoy better throttle response, a deeper exhaust note, and proven power gains for thousands of miles.