The Comp Cams Hydraulic Camshaft Upgrade: An 80 HP Project for Your Chevelle SS

If you are looking for a substantial power gain from a single engine component, a hydraulic camshaft swap is one of the most effective upgrades you can make to a classic Chevrolet V8. For a Chevelle SS owner, installing a Comp Cams hydraulic camshaft offers a proven route to unlocking roughly 80 additional horsepower at the rear wheels. While the parts and supporting hardware represent an investment in the $1,200 range, the results in terms of throttle response and mid-range torque are dramatic. This guide covers the full installation process, from selecting the right cam profile to the final break-in procedure, ensuring your project yields maximum performance and durability.

Understanding the Power Potential

The 80 horsepower gain associated with a Comp Cams hydraulic camshaft is not a universal figure. The actual increase depends on your specific Chevelle SS engine—whether it is a 396, 454, or a small-block 350. However, a well-matched hydraulic cam from Comp Cams, combined with proper valve springs and timing components, consistently delivers between 70 and 90 horsepower on a mild big-block setup. This gain comes from improved volumetric efficiency, allowing the engine to breathe more deeply at higher RPM without sacrificing the low-speed drivability that hydraulic cams provide.

Selecting the Right Comp Cams Kit

Before you purchase any parts, you must determine the correct camshaft grind for your vehicle. Comp Cams offers several families of hydraulic camshafts that are well-suited to the Chevelle SS. The most popular options include the Xtreme Energy (XE) series and the Thumpr series. For a street-driven Chevelle that sees occasional drag strip use, an XE274 or XE284 grind is a common choice. These cams have a moderate duration and lift profile that works with the factory torque converter (though a higher stall is recommended) and stock compression ratios.

Key Considerations When Choosing a Cam Profile

  • Duration at 0.050 inch lift: For a 80 HP gain without requiring a full engine rebuild, look for duration between 224 and 242 degrees. Shorter duration retains low-RPM vacuum, longer duration moves the power band higher.
  • Valve lift: Ensure your cylinder heads have adequate valve-to-piston clearance. Most Chevelle SS heads will handle up to 0.550 inches of lift without machining, but always clay-check the clearance.
  • Lobe separation angle (LSA): A 110-112 degree LSA is ideal for a balanced street/strip setup. Tighter LSAs (108-110) produce a choppier idle and peakier power, while wider LSAs (114+) smooth out the idle but reduce peak power.

Tools, Parts, and Materials

You cannot complete this installation with basic hand tools alone. Because you are installing a high-performance camshaft, precision tools and specific hardware are mandatory. Plan to gather the following items before lifting the hood.

  • Comp Cams complete hydraulic camshaft kit: Includes camshaft, lifters, valve springs, retainers, and pushrods. Comp Cams part number 08-304-8 (for big-block 454) or similar based on your CID.
  • Torque wrench: Two types—a ⅜-inch drive for small fasteners (20-150 ft-lb) and a ½-inch drive for main caps and harmonic balancer bolts (up to 250 ft-lb).
  • Camshaft installation tool: A long pilot tool or a dedicated cam gear installer. Do not use a hammer.
  • Timing chain set: Use a true double-roller timing set, such as Comp Cams part number 3100K. Stock nylon-coated gears are insufficient.
  • Gasket set: Fel-Pro or Mahle high-quality gaskets for timing cover, oil pan, and intake manifold.
  • Assembly lube: Comp Cams 159 or a high-zinc engine oil additive, such as Lucas Hot Rod & Classic Oil.
  • Inner spring compressor: To remove and install valve springs without pulling the cylinder heads.
  • Dial indicator and degree wheel: Essential for verifying cam timing and intake centerline.

Preparation Phase: Getting the Engine Ready

Proper preparation prevents unintended damage. Begin by parking the Chevelle on a level surface and engaging the parking brake. Disconnect the negative battery cable—a spark during removal of electrical connections could damage the ECU (if retrofitted) or cause a fire.

Remove the Hood and Drain Fluids

Remove the hood for access. Mark or photograph the hood hinge positions for easy realignment. Drain the engine oil and coolant. Removing the radiator may be necessary for access to the front timing cover. Place a drain pan under the oil pan and remove the drain plug. After draining, remove the oil filter and set it aside.

Auxiliary Component Removal

Remove the following to expose the front of the engine:

  • Radiator and fan shroud (if equipped)
  • Accessory drive belts, alternator, and power steering pump brackets
  • Wiring harness clips and spark plug wires (mark their positions)
  • Valve covers (label the rocker arms for reassembly)
  • Intake manifold (clean the gasket surfaces thoroughly)

Removing the Factory Camshaft

With the intake manifold and front accessories out of the way, you can access the timing cover and the old camshaft.

Take off the Timing Chain Cover

Remove the crankshaft harmonic balancer bolt using a heavy-duty puller. Once the balancer is free, unbolt the timing chain cover. You may need to gently pry the cover loose, but avoid damaging the oil pan gasket. Inspect the timing chain for slack. If the original chain stretches more than ½ inch from side to side, replacing it with a double-roller chain is critical for valve timing accuracy.

Remove the Timing Chain and Gear

Remove the camshaft sprocket bolt (hold the crankshaft with a breaker bar). Slide the timing chain and cam gear off the camshaft nose. The crankshaft gear can be left in place for now, but note the timing marks on both gears for reassembly reference.

Extract the Old Camshaft

Remove the distributor and the fuel pump pushrod (if equipped). Then, unbolt the camshaft retaining plate from the front of the engine block. Carefully slide the old camshaft out of the front of the engine. Take your time—the cam bearings are soft and can easily be damaged if the cam lobes scrape against them. If the cam resists, rotate it slightly as you pull.

Installing the Comp Cams Hydraulic Camshaft

The installation of your new Comp Cams camshaft is the most critical phase. Cleanliness is paramount. Any debris left in the block can wipe out a cam lobe within minutes of startup.

Prep the New Camshaft

Liberally apply Comp Cams assembly lube to every lobe, the distributor drive gear, and the cam bearing journals. Do not use ordinary engine oil for this step. The molybdenum disulfide content in proper assembly lube provides a sacrificial layer that protects the cam during initial startup.

Slide the Cam into Place

Using the camshaft installation tool, carefully guide the cam into the bore. The tool prevents the cam from tilting and gouging the bearings. If you do not have a pilot tool, use a long socket extension wrapped in electrical tape as a guide. Slowly slide the cam all the way into the block until the retaining plate bolt holes align.

Torque the Retaining Plate

Install the camshaft retaining plate with the bolts and torque to the factory specification—typically 18-20 ft-lb for Chevy V8s. Verify that the cam rotates freely by turning the cam gear bolt hole by hand. If it binds, you have a misalignment issue.

Install the Timing Chain and Gears

Align the crankshaft keyway to the 12-o-clock position. Align the camshaft timing mark on the new double-roller timing set to match the crankshaft gear mark. There are two common ways to set timing: straight up (dot-to-dot) or advanced 2-4 degrees. For peak torque improvement on a heavy Chevelle, advancing the cam 2 degrees is recommended. Install the chain over both gears, ensuring no slack on the tight side. Torque the cam sprocket bolt to 50-60 ft-lb and verify that both timing marks are still aligned after rotation.

Degree the Camshaft

This step is not optional. Using a degree wheel and dial indicator, rotate the engine to find the intake centerline. Compare the measured centerline to the Comp Cams specification card. If it deviates more than 1 degree, you will need to use offset cam keys or an adjustable timing set to correct the position. A cam that is off by 4 degrees can shift the powerband by 300-500 RPM, negating the benefit of your upgrade.

Valve Train Installation

With the camshaft in place and timed correctly, you must upgrade the valve train to handle the increased lift and duration.

Install New Valve Springs

Remove the old valve springs using a lever-type spring compressor. Install the Comp Cams spring kit, including the steel retainers and locks. Verify installed height using a spring height micrometer. Most Chevelle cylinder heads require a shim pack to achieve the correct installed height (typically 1.800-1.900 inches for Comp Cams springs).

Check Coil Bind Clearance

With the valve fully open (at maximum cam lift), there must be at least 0.060 inches between the spring coils. Insufficient clearance will cause the spring to stack solid, leading to immediate valve float and possible piston-to-valve contact.

Reassembly and Final Installation

Reassembly is the reverse of removal, but precision is still required.

Install New Lifters and Pushrods

Dip each new hydraulic lifter in assembly lube and insert it into its bore. Install the pushrods and rocker arms. Adjust the valve lash to zero on a hot engine. For hydraulic lifters, tighten the rocker nut until the pushrod stops spinning freely, then add an additional ½ to ¾ turn to preload the lifter plunger.

Install the Timing Cover, Oil Pan, and Intake Manifold

Use new gaskets and a thin bead of silicone on the timing cover-to-oil pan seal. Torque the oil pan bolts to 10-12 ft-lb in a crisscross pattern. Install the intake manifold with new gaskets; apply a dab of silicone at the four corners where the gasket meets the china wall.

Reinstall Accessories and Fluids

Reconnect the radiator, hoses, belts, alternator, power steering pump, and valve covers. Refill the engine with the manufacturer's recommended oil. For flat-tappet camshafts, use a 10W-40 or 10W-30 diesel oil (Shell Rotella T4) or a racing oil with 1200+ ppm zinc. Do not use energy-conserving oils they lack the anti-wear additives needed for hydraulic lifters.

Refill the cooling system with a 50/50 mix of antifreeze and distilled water. Reconnect the battery.

Initial Start-Up and Break-In Procedure

The break-in procedure is the most critical part of the entire installation. Improper break-in is the primary cause of camshaft failure in flat-tappet hydraulic applications.

Pre-Ignition Checks

  • Prime the oil system by cranking the engine with the ignition coil disconnected until oil pressure registers on the gauge.
  • Verify that the ignition timing is set to 10-12 degrees BTDC.
  • Have a helper monitor the engine while you start it.

Run-In Procedure

Start the engine and immediately raise the RPM to 2000-2500 RPM. Do not let the engine idle below 1500 RPM for the first 20 minutes. Vary the engine speed between 2000 and 2500 RPM, but never let it settle to a low idle. This high-RPM condition is essential to splash oil onto the cam lobes and break in the lifters.

After 20 minutes, shut off the engine and let it cool. Retorque the intake manifold bolts (the gaskets will settle after the first heat cycle). Check the valve lash again while the engine is hot. Re-tighten any loose rocker arms.

Final Checks and Road Testing

After the break-in, perform a thorough inspection:

  • Check for oil leaks at the timing cover and oil pan gaskets.
  • Listen for valve train noise. A slight sewing-machine sound is normal for hydraulic lifters; a loud tapping indicates a collapsed lifter or incorrect preload.
  • Verify that the coolant temperature stays within the normal range after a 15-minute idle.

Take the Chevelle for an initial test drive. Accelerate gently through first gear, then perform a moderate full-throttle pull in second gear. The 80 HP increase should be immediately noticeable in the seat of your pants. Expect the power band to have shifted upward approximately 500 RPM compared to the stock cam. The engine will produce peak horsepower around 5200-5600 RPM depending on the specific cam grind.

Note on associated costs: The typical $1,200 figure for this project includes the camshaft kit ($350-$450), a double-roller timing set ($80-$120), gaskets ($60), a high-volume oil pump ($80), and professional valve spring installation if you lack a spring compressor. If you choose to upgrade the pushrods and rocker arms to roller rockers, add another $300-$400. Comp Cams official website has a kit builder tool to price out a complete package for your exact engine code.

Conclusion

Installing a Comp Cams hydraulic camshaft on your Chevelle SS is a high-roi performance upgrade that delivers a measured 80 horsepower gain when installed with the correct timing components and supporting hardware. The project demands attention to detail during the removal of the timing cover, precise degreeing of the camshaft, and a disciplined break-in procedure. Whether you use an XE series cam for broad, street-friendly torque or a Thumpr cam for a aggressive idle sound, the result is a transformed driving experience. With proper planning and this guide as your roadmap, your $1,200 investment will pay off in the form of a Chevelle that pulls harder, sounds more aggressive, and stays reliable for tens of thousands of miles.

For additional information on valve spring selection and lobe profile comparisons, Motortrend's installation guide provides empirical dyno data on several Comp Cams grinds applied to a 454 big-block. The Chevelle forum at chevelles.com also has a dedicated thread with real-world feedback from SS owners who completed this exact project.