The Chevelle SS: Legend Meets Camshaft Upgrades

The 1970 Chevelle SS 396 remains an icon of American muscle, but even the factory L34 or LS6 engines benefit from a well-chosen camshaft upgrade. Whether you are aiming to awaken a sleepy cruiser or build a strip-ready bruiser, the camshaft is the heart of that transformation. This expanded guide compares the cost and power gains of popular camshaft upgrades for the Chevelle SS, diving deep into what each choice means for your build.

Understanding Camshaft Specifications and Their Impact

Before comparing specific cams, it is vital to understand the core parameters that define camshaft performance. A camshaft controls when the intake and exhaust valves open and close, how far they lift, and how long they stay open. The key numbers are duration, lift, lobe separation angle (LSA), and lobe centerline.

  • Duration – Measured in degrees of crankshaft rotation at the point of 0.050-inch valve lift (advertised duration is at 0.006-inch). Longer duration increases top-end power but can reduce low-end torque and idle stability.
  • Lift – The amount the valve opens, determined by the lobe profile and rocker arm ratio. Higher lift allows more air and fuel into the cylinder, but requires stiffer valve springs and careful piston-to-valve clearance.
  • Lobe Separation Angle (LSA) – The angle in cam degrees between the intake and exhaust lobe centerlines. A wider LSA (112°-114°) produces a broader torque curve and a smoother idle, while a narrower LSA (106°-108°) increases overlap, boosting top-end power but creating a rougher idle and reducing vacuum.
  • Overlap – The period when both intake and exhaust valves are open. More overlap scavenges exhaust gases at high RPM but hurts low-RPM cylinder pressure and drivability.

For a Chevelle SS, these numbers directly affect how the engine behaves from idle to redline. The factory cam on an L34 396 (around 390 horsepower) had a duration of 224° intake / 224° exhaust at 0.050-inch, with 0.480-inch lift and a 114° LSA. The LS6 454 had a hotter stick – 242°/242° duration, 0.520-inch lift, 114° LSA. Understanding these baselines helps frame the upgrade potential.

1. Stock Replacement Camshaft

A stock replacement cam is an exact duplicate of the factory cam, designed for complete restorations or budget rebuilds. While it restores original performance, the gains are negligible unless the old cam was severely worn.

  • Cost: $150 – $300 (e.g., Cloyes or Sealed Power part)
  • Power Gain: 0–15 horsepower over a worn factory cam
  • RPM Range: 1,000–5,000 RPM
  • Idle Quality: Smooth, stock vacuum levels
  • Best For: Concours restorations, daily drivers that never see WOT

Many owners find that a stock replacement cam is a missed opportunity. For a few hundred dollars more, a mild performance cam can transform the driving experience without sacrificing reliability.

2. Mild Performance Camshaft

This category includes camshafts often called "RV" or "torque" cams. They offer a noticeable bump in mid-range power while maintaining decent manifold vacuum and a tolerable lope. Popular options include the Comp Cams XE256H (duration 210°/216° at 0.050-inch, lift 0.485-inch/0.500-inch, LSA 110°) or the Lunati Voodoo 60101 (211°/219°, 0.492-inch/0.513-inch lift, 112° LSA).

  • Cost: $300 – $600
  • Power Gain: 20–30 horsepower
  • RPM Range: 1,500–5,500 RPM
  • Idle Quality: Slight lope, vacuum suitable for power brakes and wipers
  • Best For: Street-driven cars that see highway cruising and occasional spirited acceleration

These cams are compatible with stock intakes, carbs, and exhaust manifolds, though header installation will unlock the full gain. Owners report seat-of-the-pants improvement, with the engine feeling alive at lower RPMs.

3. High-Performance Camshaft

When you want to chase numbers, a high-performance camshaft moves the power band upward. This cam is the choice for the enthusiast who doesn't mind a lumpy idle and is willing to upgrade the valvetrain, intake, and carburetor. A good example is the Comp Cams XE274H (230°/236° duration at 0.050-inch, 0.487-inch/0.490-inch lift, 110° LSA) or the Crower Cams 40330 (235°/240°, 0.530-inch/0.530-inch lift, 108° LSA).

  • Cost: $600 – $1,200
  • Power Gain: 40–60 horsepower
  • RPM Range: 2,500–6,500 RPM
  • Idle Quality: Noticeable lope, requires vacuum pump or upgraded booster for brakes
  • Best For: Weekend warriors, bracket racers, show cars that are driven regularly

These camshafts demand supporting modifications: double valve springs, hardened pushrods, screw-in studs, and often a higher stall torque converter (at least 2,800–3,200 RPM). They also require a matching carburetor (750 CFM or larger) and an intake manifold designed for high-RPM airflow. Without these, the engine will be lazy below 3,000 RPM.

4. Race Camshaft

The race camshaft sacrifices any pretense of street manners. With duration exceeding 250° at 0.050-inch and lift over 0.600-inch, these cams move the power peak above 6,000 RPM. Examples include the Isky 500 Mega Cam (250°/256°, 0.625-inch lift, 106° LSA) or the Lunati 401B3 (252°/258°, 0.620-inch/0.630-inch lift, 108° LSA).

  • Cost: $1,200 – $2,500
  • Power Gain: 60+ horsepower (often 80–100 on a properly built big-block)
  • RPM Range: 3,500–7,500 RPM+
  • Idle Quality: Aggressive, requires significant tuning and high idle speed (1,000+ RPM)
  • Best For: Dedicated race cars, drag racing, high-rpm applications

Installing a race cam on a street-driven Chevelle SS without a fully built short-block, roller cam conversion, and a high-stall converter will result in disappointment. The engine will be gutless off idle, overheat in traffic, and may not run on pump gas with the necessary compression ratio.

Cost vs. Power: A Practical Comparison

To make an informed decision, it helps to see the cost-per-horsepower for each category. The following comparison assumes a typical 396 or 454 Chevelle SS engine in good condition, using aftermarket headers and a dual-plane intake where recommended. Installation labor is not included, as it varies widely (allow $600–$1,200 for a professional cam swap).

Camshaft Category Cam Cost (est.) Approx. Power Gain Cost per HP Additional Parts Needed Total Project Cost (mid-range)
Stock Replacement $200 10 hp $20/hp None $200
Mild Performance $450 25 hp $18/hp Valve springs, gaskets $700–$900
High-Performance $900 50 hp $18/hp Springs, pushrods, timing set, intake/carb, converter $2,500–$3,500
Race Cam $1,800 80 hp $22.50/hp Full valvetrain, roller setup, forged internals, ECU tune (if EFI) $5,000–$8,000+

Notice that the mild and high-performance cams offer similar cost-per-horsepower, but the high-performance cam requires significantly more supporting mods. The race cam shows a higher cost-per-horsepower largely because the foundation must be much stronger. For the Chevelle SS owner on a budget, the mild performance cam provides the best value per dollar spent when factoring in total project cost.

Factors Influencing Camshaft Selection

Engine Displacement and Compression

The Chevelle SS came with 396, 402, 454, and even 427 ci engines. A larger displacement engine can handle longer duration cams without losing low-end torque because the cubes help fill the cylinder. Low compression (under 9.5:1) favors a cam with shorter duration and earlier intake valve closing to build cylinder pressure. High compression (10.5:1+) can handle aggressive profiles with later intake closing. A mismatch will yield flabby power or detonation.

Intended Use: Street vs. Strip vs. Show

If you commute in your Chevelle, a cam with duration over 230° at 0.050-inch and narrow LSA becomes painful in traffic. The reduced manifold vacuum kills power brakes and wipers, and the engine may idle at 1,200 RPM. For pure drag racing, you can tune around these issues, but for street enjoyment, choose a cam that makes power between 2,000 and 5,500 RPM. Many owners split the difference with a "street/strip" cam in the 220°–230° range.

Compatibility with Supporting Mods

A camshaft does not work alone. The intake manifold, carburetor, cylinder heads, exhaust, and even the transmission stall speed must match. A common mistake is installing a high-performance cam on a stock 396 with 2.19-inch intake valves and a 750 CFM carburetor, only to find the power band moves too high for the stock converter. A good rule of thumb: the cam's intended RPM range should align with the converter's flash stall speed. For example, a cam that makes peak power at 5,800 RPM needs a converter that stalls at 3,000–3,500 RPM.

Valve Train Modifications Required

Every cam upgrade above a stock replacement demands better valve springs. A cam with over 0.500-inch lift will exceed the stock spring's ability to control the valve, leading to float and failure. Additional items include hardened pushrods, roller rocker arms (optional but recommended), and a double-roller timing chain set. The race cam often requires a full roller cam conversion (with lifter, pushrod, and rocker upgrades) plus piston flycutting to clear valves. These costs add up quickly.

Installation and Tuning Considerations

Installing a camshaft in the Chevelle SS's big-block is a major job: remove the radiator, front grille, timing cover, valve covers, intake manifold, rocker arms, and pull the distributor. The cam itself slides out from the front after removing the timing chain. Owners with moderate mechanical skill can do it in a weekend, but proper installation requires checking piston-to-valve clearance if the cam has high lift or if the pistons have deep valve reliefs.

Tuning after the swap is critical. The carburetor may need a different power valve, accelerator pump cam, and jetting to match the new vacuum signal. Ignition timing should be re-curved, often with a total timing of 34°–38° all-in by 3,000 RPM. Vacuum advance should be adjusted for idle vacuum. If the car still has a points-distributor, an electronic conversion (e.g., MSD or Pertronix) ensures a strong spark at high RPM. For the race cam, a crank-trigger ignition and timing control become useful.

Real-World Dyno Results and Owner Feedback

Data from enthusiast forums and magazine builds provides concrete examples. A 1970 Chevelle SS 396 (L34, 350 hp factory) with 9.0:1 compression and headers gained 24 horsepower with a Comp Cams XE256H (mild) – from 330 to 354 hp at the wheels. The same car, after adding aluminum heads and a high-performance Comp XE274H, gained 52 horsepower, peaking at 382 hp, but the idle was rough and vacuum dropped to 9 inHg, requiring a vacuum reservoir for headlights.

Another builder with a 454 LS6 (450 hp factory) installed a Lunati Voodoo 60103 (duration 219°/227° at 0.050-inch, lift 0.515″/0.530″, 112° LSA) and saw a 35-hp wheel gain while retaining good street manners. He spent $550 on the cam and $200 on springs, for a total investment of $750 yielding 35 hp – about $21/hp. In contrast, a full race build with a Comp Cams Roller 248°/254° (0.650″/0.650″ lift) cost over $6,000 including CNC-ported heads and a custom intake, and produced 580 hp at the crank – a gain of 130 hp from the LS6 stock, but at $46/hp for the entire package.

Recommendations Based on Budget and Goals

Budget Build (Under $500)

If you want to freshen the engine without breaking the bank, a mild performance cam like the Comp Cams XE256H or the Lunati Voodoo 60101 is ideal. Pair it with new valve springs and a timing set. Expect 20–30 horsepower gain and a satisfying but mild lope.

Street Performance Build ($2,000–$3,500)

For a Chevelle that sees regular street use but can handle stoplight battles, select a high-performance cam in the 230° duration range at 0.050-inch. Upgrade to aluminum heads or port your iron heads, install a dual-plane intake like the Edelbrock RPM, a 750–800 CFM carburetor, and a 3,000 RPM stall converter. The Crower 40330 or Comp XE274H are proven picks. This combination yields 50+ horsepower and transforms the car into a true street predator.

Strip-Bound Build ($5,000+)

If you live at the track and trailer your Chevelle, skip hydraulic cams and go to a solid roller. The Isky 500 Mega Cam or a custom grind from a reputable company like Comp Cams is essential. You will need a fully built short-block (forged pistons, billet rods, stud girdle), a sheet-metal intake, a Dominator carburetor, a trans brake, and a 4,500+ RPM converter. The power gain is massive, but so is the noise and maintenance.

Final Thoughts

Choosing a camshaft for your Chevelle SS is not just about peak power numbers – it is about matching the cam to the vehicle's purpose and your willingness to modify the rest of the drivetrain. The mild performance cam and high-performance cam offer the best power per dollar for a street-driven classic. The race cam is for the obsessed. By understanding the specs, costs, and required supporting parts, you can make a choice that keeps your Chevelle SS running strong, whether you are cruising to a car show or lining up at the dragstrip.

For further reading, consult the factory Chevrolet service manuals and online communities like Chevelle Tech or Team Chevelle. Real advice from owners who have already swapped cams is invaluable. With the right camshaft, your Chevelle SS will deliver the power and sound that make these cars legendary.