Stock 6.4 Hemi Camshaft: A Baseline for Performance

The factory camshaft in the 6.4L Hemi (392) is a well-engineered component designed to deliver a solid balance of power, fuel economy, and daily-driver refinement. With a duration of 218/230 degrees (intake/exhaust), valve lift of .512 inches, and a lobe separation angle (LSA) of 115 degrees, the stock cam prioritizes low-end torque and smooth idle quality. This makes it ideal for trucks, SUVs, and sedans that need towing capability or a civilized driving experience.

However, the stock cam leaves considerable headroom on the table for those chasing peak horsepower. The wide LSA and moderate duration limit how much air the engine can ingest at higher RPM, capping the 6.4 Hemi’s potential. For enthusiasts seeking track-day performance or spirited street driving, upgrading to a more aggressive cam profile like the Comp Cams XE270HR can unlock substantial gains.

Comp Cams XE270HR: Purpose-Built for Power

The Comp Cams XE270HR is a high-performance hydraulic roller camshaft specifically engineered for the Gen III Hemi (including 6.4L). Its aggressive lobe profile features 270/276 degrees of duration (advertised) and .600-inch valve lift, paired with a tighter 110-degree LSA. This design shifts the power band upward, prioritizing mid-range and top-end horsepower while still maintaining acceptable street manners.

Key Specifications Comparison

Parameter Stock Cam Comp Cams XE270HR
Intake Duration (advertised) 218° 270°
Exhaust Duration (advertised) 230° 276°
Valve Lift (intake/exhaust) .512 in .600 in
Lobe Separation Angle 115° 110°
Valve Overlap Low (street-friendly) Moderate-aggressive
Intended Use Daily driving, towing Performance street/strip

Note: Duration values from Comp Cams use their advertised duration rating. Manufacturers may measure differently, so always verify with the cam card.

Real-World Horsepower Gains: 50+ HP Breakdown

Dyno results from various shops and forum builds confirm that the XE270HR can add 50–65 horsepower at the wheels on a properly tuned 6.4 Hemi. The gains come from several factors:

  • Increased airflow: Higher lift and longer duration allow the engine to inhale more air-fuel mixture per cycle, especially above 4,500 RPM.
  • Optimized valve timing: The tighter LSA reduces overlap at low RPM but increases it mid-range, improving cylinder scavenging for a stronger torque punch.
  • Higher RPM ceiling: The stock cam signs off around 5,500–5,800 RPM. The XE270HR pulls strongly to 6,500+ RPM, adding usable horsepower at the top end.

A typical before/after dyno chart shows the stock engine making ~400–410 whp (depending on drivetrain) and the cammed engine hitting 455–470 whp with supporting mods. That’s a genuine 50+ wheel horsepower gain—enough to transform the character of the vehicle.

Supporting Modifications: The Must-Have List

Installing an aggressive cam like the XE270HR without supporting parts is a recipe for disappointment. Here’s what you need to pair with the cam for reliable, maximum output:

1. Valve Spring Upgrade

The stock valve springs cannot handle .600-inch lift at high RPM—coil bind occurs below 6,500 RPM, risking valve float and catastrophic engine damage. Upgrade to dual or beehive springs rated for at least .650-inch lift (e.g., Comp Cams 26926-16 or Mopar Performance springs).

2. Pushrods

A longer cam base circle often requires different pushrod lengths. After measuring with an adjustable pushrod, select hardened pushrods (e.g., Smith Brothers or Manton). Expect to add ~.050–.100 inch to the length.

3. Cam Phaser Limiter (VVT Models)

If your 6.4 Hemi uses variable valve timing (VVT), you’ll need a phaser limiter kit (e.g., MMX or Ripp Superchargers) to prevent the PCM from advancing the cam too far and causing piston-to-valve contact. Some builders convert to a non-VVT timing chain setup for simplicity.

4. Fuel System

The stock fuel injectors and pump may suffice for 470–490 whp, but at the 500+ whp threshold, injector duty cycles hit 95%+. Consider upgrading to 60 lb/hr or larger injectors and a higher-flow in-tank pump if you plan further mods.

5. Exhaust System

To let the engine breathe, pair the cam with headers (long-tube preferred), a full 3-inch exhaust, and high-flow catalysts or off-road pipes. The stock exhaust manifold is restrictive—gains of 15–20 hp are common from headers alone.

6. Cold Air Intake

A high-flow intake (e.g., Mopar or Volant) helps deliver the increased air demand. Expect 5–10 hp improvement on a cammed engine.

Tuning: Unlocking the Cam’s Full Potential

No modern Hemi runs properly after a cam swap without a custom ECU tune. The stock calibration won’t handle the altered VE tables, fuel requirements, or timing curve. Use a standalone programmer (HP Tuners, SCT) or a reputable remote tuner. Key tuning adjustments include:

  • Fuel tables: Add enrichment at high RPM and under load to maintain proper air-fuel ratio (target 12.5:1 on naturally aspirated).
  • Ignition timing: Advance timing by 2–4 degrees at peak torque, but watch for knock. The XE270HR’s higher cylinder pressure may require retarding timing near redline.
  • Idle stability: Tighten idle speed to 850–950 RPM and adjust IAC/target airflow to manage lope. Expect a noticeable chop.
  • Transmission tuning: For automatic vehicles, raise shift RPM 200–300 higher than stock and increase line pressure to handle added torque.

Warning: Driving with a stock tune after a cam swap can cause lean misfires, pre-ignition, and catalytic converter damage. Always tune before first start.

Installation Guide: Step-by-Step Overview

Cam installation is not a beginner-level job—plan for 8–12 hours of labor in a well-equipped shop. Here’s a condensed procedure:

  1. Disconnect battery and drain coolant. Remove intake, radiator, and accessories for access.
  2. Remove timing cover and timing chain. Scan the phaser (if VVT) or sprocket alignment.
  3. Support the valve train by removing rocker arms and pushrods. Use a valve spring compressor to remove stock springs and retainers.
  4. Replace lifters – Even if using the VVT phaser, match the cam’s lobe profile with high-performance lifters (avoid reusing old ones).
  5. Slide out the stock cam carefully to avoid nicking cam bearings. Install the new cam with generous assembly lube on each lobe.
  6. Install new timing equipment (chain, tensioner, guides) and phaser limiter if applicable. Degree the cam to verify timing.
  7. Install upgraded valve springs, retainers, and keepers. Reassemble pushrods and rocker arms with proper torque.
  8. Reassemble all accessories, refill fluids, and prime the oil system by cranking with the fuel pump fuse removed until oil pressure builds.
  9. Start engine and let it idle for 20 minutes to break in the cam lobes (if using flat-tappet solids—but roller cams need only normal break-in).
  10. Perform initial tuning via a remote tuner or dyno session.

Note: Wear and break-in procedures differ between hydraulic roller and flat-tappet cams. The XE270HR is a hydraulic roller; modern roller cams require minimal break-in, but always confirm with the cam manufacturer’s instructions.

Drivability Trade-Offs: What You Sacrifice

The XE270HR brings impressive power but also changes daily-driver character:

  • Rough idle: Lope is pronounced due to the 110° LSA and increased overlap. The engine may vibrate at stoplights.
  • Reduced low-end torque: Below 2,000 RPM, the cam is lazy—around town you’ll need more throttle input. Not ideal for heavy trucks or towing.
  • Higher noise: Valve train noise increases with spring pressure and lobe aggression. Expect a mechanical “tick” at idle.
  • Fuel economy drop: Expect 2–4 mpg less on the highway, and worse in stop-and-go traffic.
  • Maintenance: More frequent oil changes (with high-ZDDP oil) are recommended to protect the cam lobes and lifters.

If you’re building a weekend warrior or track car, these trade-offs are acceptable. For a daily driver that sees long commutes, consider a milder cam like the Comp Cams XR265HR or the Magnum 230/234 offering better balance.

Alternatives to the XE270HR

The XE270HR is one of many cams for the 6.4 Hemi. Other popular options include:

  • Comp Cams XR265HR: 265/271 duration, .575 lift, 112 LSA. Gains ~35–45 hp with better street manners than the XE270HR.
  • Magnum 230/234: 230/234 @ .050, .600 lift, 111+3 LSA. Designed for VVT engines and pairs with phaser limiters.
  • Cam Motion Custom Grinds: Tailored profiles for specific builds (drag racing, road course, towing).
  • Stock cam with VVT tune: A simple tune can unlock 10–15 hp without sacrificing drivability—cheapest option.

For 50+ HP, the XE270HR remains a proven winner. However, if you keep VVT, you may prefer a cam that works with the factory phaser, like the Magnum 230/234 or a custom grind from Comp Cams specifically designed for VVT.

Installation Parts List: What You’ll Need to Buy

Essential Components

  • Comp Cams XE270HR camshaft (P/N 273HR-110 for non-VVT; check compatibility)
  • Valve spring upgrade kit (e.g., Comp 26926-16 or PAC 1200x)
  • Hardened pushrods (length measured per build)
  • High-performance hydraulic roller lifters (stock can be reused, but aftermarket is recommended)
  • Timing chain set (Mopar Performance or Cloyes)
  • Cam phaser limiter (if VVT) – MMX VVT Cam Lockout Kit

Optional Upgrades

  • Long-tube headers (e.g., American Racing Headers or Kooks)
  • 3-inch exhaust system
  • Cold air intake
  • Upgraded fuel injectors (60 lb/hr)
  • Higher stall torque converter (2,800–3,200 RPM for automatics)

Dyno Results: Real-World Data

Borrowing from a well-documented build on HemiTruckClub, a 2018 Ram 1500 with the 6.4 Hemi (8HP70 transmission) baseline pulled 396 whp. After installing the XE270HR, ported heads, Kooks headers, 3-inch exhaust, and proper tune, the truck made 467 whp at 6,400 RPM—a gain of 71 whp. Even without head work, gains of 50–55 whp are typical.

Another example on a 2021 Durango SRT showed a jump from 445 to 509 crank horsepower (flywheel), confirming the 50+ HP claim. Always remember: dyno numbers vary by correction factor, weather, and dyno model, but the trend is undeniable.

Frequently Asked Questions

Will the XE270HR work with stock headers?

Yes, but you’ll leave 15–25 hp on the table. The stock exhaust manifold is restrictive above 5,500 RPM. For full gains, step up to long-tube headers.

Do I need a new torque converter?

With an automatic transmission, the stock converter is typically 1,800–2,000 RPM stall. A 2,800–3,200 RPM stall converter will keep the engine in the power band from launch, greatly improving ETs. For street driving, a 2,800 RPM stall is a good compromise.

Will the cam pass emissions?

With a proper tune and high-flow cats, the XE270HR may pass a tailpipe test if idle CO levels are tuned correctly. However, the aggressive lope may attract attention during a visual inspection. Check local laws.

Is the XE270HR compatible with E85?

Yes, with injector and fuel pump upgrades. E85 has higher octane and cooling effect, allowing more timing advance—potential for another 15–20 hp.

Conclusion: Is the XE270HR Right for You?

The Comp Cams XE270HR delivers genuine 50+ rear-wheel horsepower gains in the 6.4 Hemi, transforming the engine from a torque-heavy cruiser into a high-revving performer. It requires significant supporting modifications, professional installation, and custom tuning. The trade-off in low-end torque and idle quality is real, but for enthusiasts who prioritize track passes or street thrill, the juice is worth the squeeze.

If you’re building a dedicated performance vehicle—especially one with manual transmission or a stall converter—the XE270HR is a top contender. For those who need daily-driver civility, consider a milder grind. Either way, plan your budget carefully—the cam itself is under $500, but supporting mods, labor, and tuning can quickly push the total to $3,000–$5,000. For more details, visit Comp Cams’ Hemi page or consult a reputable engine builder who specializes in Gen III Hemi platforms.