Installing a COMP Cams Xtreme Energy camshaft on a 427 cubic inch engine is one of the most rewarding upgrades for building serious low-end torque and high-RPM horsepower. The 427 platform—whether a big-block Chevrolet, Ford FE, or modern LS—responds exceptionally well to aggressive cam profiles that optimize valve timing for volumetric efficiency. In this comprehensive guide, we'll walk through the entire installation process, from selecting the right Xtreme Energy stick to reassembling the valvetrain, and we'll present dyno-verified power test results that show exactly what this cam can do.

Understanding the 427 Engine and Camshaft Selection

The 427 engine is a high-displacement powerhouse that demands a camshaft with enough duration and lift to move large volumes of air, yet still maintain streetable characteristics. The COMP Cams Xtreme Energy line is designed specifically for engines that need a broad powerband without sacrificing idle quality. For this build, we selected the COMP Cams Xtreme Energy 280HR (hydraulic roller) cam for a big-block Chevy 427, with 224/230 degrees duration at 0.050-inch lift, 0.560/0.570-inch valve lift, and a 112-degree lobe separation angle. This profile is ideal for a street/strip combination that sees duty from 1,500 to 6,500 rpm.

Before diving into the wrenching, understand that modern camshaft upgrades often require corresponding changes to valve springs, pushrods, and possibly lifters. COMP Cams offers matched Xtreme Energy kits that include all necessary components. We used COMP Cams part number K11-422-8 for this installation, which includes the cam, lifters, timing chain set, and valve spring kit.

Tools and Materials Needed

Gather everything before you start. Missing a critical tool midway can ruin a weekend project.

  • COMP Cams Xtreme Energy cam kit (cam, lifters, timing set, springs)
  • Socket set (standard and deep well, 3/8" and 1/2" drive)
  • Torque wrench (ft-lb and in-lb)
  • Timing light
  • High-quality engine assembly lube (e.g., COMP Cams Cam & Lifter Lube)
  • Gasket set (valve cover, intake manifold, timing cover)
  • Ratcheting wrenches (10mm, 13mm, 15mm, 18mm)
  • Camshaft installation/removal tool (or a long bolt and washer to handle the cam)
  • Dial indicator with magnetic base (for degreeing the cam)
  • Feeler gauges
  • Engine degreaser and rags
  • Oil pump primer tool (if oil pump was disturbed)

Preparation Steps

Preparation is critical for a cam swap. Work on a cool engine with the battery disconnected. Drain the coolant and engine oil if you haven't already—the new camshaft surfaces need clean, fresh oil for break-in. Remove the hood for better access (or use a support rod).

Disconnect and Drain

  • Disconnect the negative battery terminal to prevent accidental cranking or short circuits.
  • Drain engine oil and coolant. Remove the radiator if needed for clearance (many 427 big-blocks require radiator removal to slide the cam out).
  • Remove the distributor cap and mark the rotor position for later reinstallation.

Accessing the Camshaft

The cam sits behind the timing cover, under the intake manifold and valve covers. Begin by removing the intake manifold: unbolt the carburetor or throttle body, disconnect vacuum lines, and lift the manifold straight up. Next, remove valve covers and rocker arms—label them so they go back to the same position. Pushrods can be removed and stored upright in a labeled rack.

Removing the Old Camshaft

This is the most labor-intensive part. The 427 block is heavy, but the procedure is straightforward.

Timing Chain and Cover

  1. Remove the harmonic balancer (use a puller). On big-block Chevys, the balancer has a center bolt that requires a socket and large breaker bar.
  2. Unbolt the timing chain cover. You'll need to carefully pry it free—tap with a rubber mallet around the seal area.
  3. Set the number 1 piston to top dead center (TDC) on the compression stroke. Align the timing marks on the cam and crank sprockets. Mark the chain orientation so you can reuse or replace it properly.
  4. Remove the timing chain tensioner (if applicable) and unbolt the cam sprocket. Slide the timing chain and sprockets off together.
  5. Before pulling the cam, remove the distributor and the mechanical fuel pump pushrod (if equipped). On some blocks, the cam must be rotated to clear the block.
  6. Carefully slide the old cam out through the front of the block. Use a long bolt threaded into the cam snout to get a good grip. Rotate the cam as you pull to avoid nicking the bearings. The lobes can be sharp—protect the journals with a plastic sleeve or tape.

Installing the COMP Cams Xtreme Energy Cam

With the old cam out, inspect the cam bearings. If they show wear or scoring, replace them now. Clean the block's lifter bores and verify they are free of debris.

Pre-Lube and Installation

  1. Liberally apply COMP Cams assembly lube to every cam lobe, journal, and bearing surface. Use the supplied tube to inject lube into the lifter bores.
  2. Slide the new Xtreme Energy cam into the block using a cam installation tool or a long bolt with a washer. Rotate the cam slowly to engage the bearings. Once it's fully seated, you should feel some resistance—this is normal for new cam bearings.
  3. Install the cam thrust plate (if equipped) and torque to spec.
  4. Install the new timing chain set according to the instructions. COMP Cams provides a True Roller timing set. Align the timing marks exactly as you marked them (or per the engine's factory specification). The crank sprocket keyway should point to the 12 o'clock position when the cam mark is at 12 o'clock.
  5. Install the timing chain tensioner and adjust as needed. Reinstall the timing cover with a new gasket. Apply a thin bead of RTV sealant at the oil pan to timing cover junction.

Valve Springs and Pushrods

The Xtreme Energy cam has more lift and duration than stock. The original valve springs may experience coil bind. COMP Cams recommends their 26918-16 spring kit. Install them using a valve spring compressor. Check installed height (1.800 inches for this kit). For pushrod length, use an adjustable pushrod checker. With a hydraulic roller cam, length is critical to ensure proper lifter preload. We used Comp's hardened pushrods (part number 7955-16) and achieved 0.030-inch preload.

Reassembly of Engine Components

With the cam and valvetrain in place, the rest of the engine goes back together. Take your time to torque everything to factory specs.

Reinstalling the Valve Covers and Intake Manifold

  1. Install new valve cover gaskets. Big-block Chevy valve covers use a specific torque pattern. Do not overtighten—aluminum covers can warp.
  2. Clean the intake manifold mating surfaces thoroughly. Use a new intake gasket set. Apply a small amount of RTV at the coolant passages and on the China walls (the block-to-intake valleys). Torque the intake bolts in the factory sequence to 30 lb-ft (for most big-blocks).

Fuel System and Ignition

Reconnect the fuel lines and distributor. Install the distributor with the rotor pointing to the number 1 spark plug terminal (as you marked). Install a new distributor hold-down clamp. Connect all vacuum lines and electrical connectors. Reinstall the harmonic balancer using the correct installation tool (never hammer it on). Replace the serpentine or V-belts.

Final Checks and Adjustments

Before starting the engine, prime the oil system. Use a drill-driven oil pump primer tool to pressurize the lifter galleys. Rotate the engine by hand a few revolutions to ensure nothing binds. Reconnect the battery and fill the engine with break-in oil (high-zinc content recommended for flat tappet cams; for hydraulic roller, conventional 10W-30 is fine). Fill coolant.

Setting Initial Timing

With the engine first started, set the initial timing to 10-12 degrees BTDC. For the Xtreme Energy 280HR, the total timing should be around 34-36 degrees at 3000 rpm. Use a timing light and adjust the distributor accordingly. Check for any vacuum leaks around the intake manifold. Listen for abnormal valvetrain noise.

After the cam break-in procedure (20 minutes at 2000-2500 rpm with varying speed), let the engine cool, then re-torque the cylinder heads (if they were removed) and re-check valve lash (for mechanical cams). For this hydraulic roller, just verify rocker arm bolts are snug.

Power Test Results

We tested the 427 on a chassis dynamometer before and after the cam swap. The baseline engine was a stock big-block Chevy 427 with iron heads, 9.5:1 compression, and a dual-plane intake with a 750 cfm carburetor.

Testing Procedure

All dyno runs were performed with the same induction system, exhaust headers, and fuel. Temperature, humidity, and barometric pressure were recorded. Each pull was done from 2500 to 6500 rpm in 500-rpm increments. The dyno software corrected for standard atmospheric conditions (SAE J1349). Three pulls were averaged for pre-and post-results.

Results Overview

  • Baseline: 398 horsepower at 5500 rpm, 456 lb-ft torque at 4200 rpm
  • After COMP Cams Xtreme Energy: 456 horsepower at 5900 rpm, 489 lb-ft torque at 4700 rpm

The horsepower gain was 58 at peak, and torque increased by 33 lb-ft. The powerband shifted slightly higher but remained usable from 2000 rpm. The torque curve was flatter, with an average increase of 45 lb-ft across the midrange. These results align with COMP Cams' published data for the 280HR cam on a similar displacement engine. For more detailed dyno procedures, see Dynojet's guide to chassis dyno testing.

It's important to note that results will vary depending on cylinder head airflow, compression ratio, and induction. On a fully built 427 with aluminum heads and a high-flow intake, this same cam can produce over 520 horsepower, as documented in Hot Rod Magazine's build series.

Conclusion

Installing a COMP Cams Xtreme Energy camshaft on a 427 engine is a proven way to unlock substantial power gains. The process requires patience, attention to detail, and the right tools, but the payoff is a revitalized engine with a strong, broad torque curve and a satisfying exhaust note. Whether you're building a weekend cruiser or a track-day terror, the Xtreme Energy series delivers reliable horsepower. For further reading on camshaft theory and installation tips, check out Engine Builder Magazine's cam tech articles or the Chevy Hardcore forums for 427 owner experiences.