The Chevy Big Block 396 is a legendary engine that has captivated muscle car enthusiasts for decades. Known for its raw power and robust design, many owners seek ways to unlock its full potential. One of the most effective modifications is a camshaft upgrade. In this article, I’ll share my hands-on experience with a $1,500 Summit Racing Cam Kit that completely transformed my Big Block 396, boosting performance, throttle response, and that iconic exhaust note.

Understanding the Chevy Big Block 396

Introduced in 1965 as part of Chevrolet’s Mark IV big-block family, the 396 cubic-inch V8 quickly became synonymous with American muscle. It powered iconic cars like the Chevrolet Chevelle SS, Corvette, and Impala SS. With a factory rating ranging from 325 to 375 horsepower in its prime (and even higher in some race variants), the 396 was a torque monster. Its deep-skirt block, forged steel crankshaft, and heavy-duty connecting rods built a reputation for durability. However, decades of evolution in engine technology mean that these classic engines can benefit greatly from modern performance parts.

One of the most cost-effective ways to wake up a 396 is through camshaft replacement. The original camshafts were designed for smooth idle, emissions compliance, and longevity, not peak horsepower. A modern aftermarket cam kit can dramatically improve airflow, increase valve lift and duration, and shift the power band to where you want it.

For a deep dive into the history of the 396, check out this Hemmings article on the 396’s legacy.

Why Upgrade Your Camshaft?

The camshaft is the brain of your engine, controlling when the intake and exhaust valves open and close. Stock cams are conservative, limiting the engine’s ability to breathe. Upgrading to a performance camshaft offers several key benefits:

  • Increased horsepower and torque – More aggressive lift and duration allow more air-fuel mixture into the cylinders.
  • Improved throttle response – Faster valve events create a sharper, more immediate reaction.
  • Enhanced engine sound – That iconic loping idle is a direct result of increased overlap.
  • Better overall performance – Matched with supporting mods, a cam can make your car feel like a new machine.

But it’s not just about power. A camshaft also affects the engine’s power band. A short-duration cam with moderate lift will keep power lower in the RPM range, ideal for street driving. A longer-duration, high-lift cam moves power higher, which is great for track use. Choosing the right spec is critical.

For a technical overview of camshaft theory, EngineLabs explains camshaft fundamentals.

Choosing the Right Cam Kit for Your 396

When I decided to upgrade my 396, I knew I wanted a combination of streetable manners and serious power gains. After researching several options, I settled on the Summit Racing Cam Kit (Part #SUM-K6401). This kit is specifically designed for big-block Chevy engines (396, 427, 454) and includes everything needed for a complete cam swap:

  • High-performance hydraulic flat-tappet camshaft with 0.510” intake / 0.510” exhaust lift and 280° advertised duration
  • Matching valve springs rated for the cam’s lift
  • Retainers, locks, and valve stem seals
  • Camshaft gear and timing chain set
  • Assembly lube and detailed instructions

At just under $1,500, this kit delivers exceptional value compared to buying separate components from specialty brands. The cam’s specs are a proven blend: enough lift to wake up the heads, enough duration to move the power band slightly higher, yet still compatible with stock or mild aftermarket intake and exhaust systems. I opted to pair it with a Summit Racing intake manifold and a set of headers to fully realize the gains.

Before you buy, consider your existing setup. Are your heads stock? Do you have a good dual-plane intake? What about compression ratio? The cam I chose works well with 9.5:1 to 10.5:1 compression, which covers most street 396s. If you’re running higher compression or a roller cam conversion, you’ll want different specs.

You can view the exact kit on Summit Racing’s product page for current pricing and specs.

Installation Process: Step-by-Step

Installing a camshaft is not a beginner-level job, but with patience, proper tools, and a good manual, it’s doable in a home garage over a weekend. Here’s how I tackled it on my 396:

Preparation

  • Budget for a complete timing cover gasket set, valve cover gaskets, intake gaskets, and fresh oil filter.
  • Gather tools: socket set, torque wrench, camshaft degree kit (recommended), piston stop tools, dial indicator, and a harmonic balancer puller.
  • Set engine to top dead center (TDC) on the compression stroke for cylinder #1. Mark the balancer and timing cover for reference.

Removing the Old Camshaft

  1. Drain coolant and remove the radiator if necessary for clearance. On many 396s, especially in early Chevelle or Nova engine bays, the cam will slide out the front.
  2. Remove the intake manifold, valve covers, rocker arms, and pushrods. Mark everything for reinstallation order.
  3. Take off the harmonic balancer and timing cover. Remove the timing chain and gears.
  4. Carefully slide out the camshaft. Support it to avoid damaging cam bearings.
  5. Remove the valve springs using a spring compressor. Keep the valves closed by pressurizing the cylinder with compressed air through the spark plug hole.

Installing the New Summit Racing Cam Kit

  1. Lubricate the camshaft lobes and journals generously with the included assembly lube. Insert the cam carefully, rotating it as you go.
  2. Install the new timing chain and gears, aligning the dots per instructions. I double-checked cam timing with a degree wheel and dial indicator – you want the intake lobe centerline within 1-2 degrees of spec.
  3. Install the new valve springs, retainers, and locks. Set the installed height and check seat pressure (Summit’s kit specs are designed to work without shimming, but verify when assembled).
  4. Reinstall the pushrods and rocker arms. Adjust rocker arm lash to manufacturer spec (typically 0.022” hot for hydraulic cams, but Summit recommends preload method for hydraulic lifters).
  5. Reinstall the intake manifold with new gaskets, torque the bolts in sequence.
  6. Attach the timing cover, harmonic balancer (apply thread locker to the bolt), and valve covers.
  7. Reconnect coolant system and fill with fresh antifreeze.
  8. Install new oil filter, fill with quality 10W-30 (break-in oil recommended for flat-tappet cams).

Break-In Procedure

After installation, run the engine at 2000-2500 RPM for 20 minutes, varying RPM slightly. This seats the cam lobes and lifters. Do not let it idle during break-in. Use a high-zinc break-in oil additive if your oil doesn’t have ZDDP.

For a more detailed walkthrough, Hot Rod’s cam installation guide covers the basics for big-block Chevys.

Performance Results: Before and After

I had my engine on a chassis dyno before the swap and after the swap (with the same carburetor and exhaust system). The difference was night and day:

  • Horsepower: Peaked at 340 HP at the wheels stock. After the cam kit, it hit 405 HP – a gain of 65 peak HP. More importantly, power was up across the board from 2500 RPM to redline.
  • Torque: Peak torque rose from 440 lb-ft to 500 lb-ft, and the torque curve was broader. The engine now pulls hard from 2000 RPM all the way to 5500 RPM.
  • Throttle response: The engine revs more freely. A quick jab of the throttle snaps the tach needle up instantly.

While every setup varies, these numbers are typical for a well-built 396 with a moderate cam. The Summit kit’s .510 lift and 280° duration are well-matched to stock iron oval-port heads (which flow decently up to about .500-.550 lift). If your 396 has closed-chamber rectangular-port heads, you could see even more.

Sound and Driving Experience

The exhaust note is arguably the most satisfying part. At idle, the cam produces that classic muscle-car lope – the engine rocks side to side, and the sound is aggressive but not obnoxious. Under light throttle, it still cruises smoothly. But when you step on it, the sound hardens into a bellow that turns heads.

Driving the car on the street, the power delivery is addictive. It pulls strongly from off-idle, and the mid-range torque makes passing effortless. I did notice a slight loss of low-end below 1500 RPM compared to stock, but that’s typical for any bigger cam. With 3.55 rear gears and a 2800 stall converter, the car launches hard and never feels lazy.

Considerations and Supporting Mods

To get the most from your cam upgrade, consider these points:

  • Heads: Stock 396 heads have okay flow, but a little port work or a set of aftermarket aluminum heads (e.g., AFR or Edelbrock) will unlock another 30-50 HP.
  • Intake manifold: An aluminum dual-plane intake like the Edelbrock Performer RPM or Summit’s own matches this cam perfectly.
  • Exhaust system: Headers and a free-flowing exhaust are essential. I used 1 7/8” primary headers and 3” exhaust with Magnaflow mufflers.
  • Fuel system: Ensure your carburetor is sized correctly. A 750 CFM vacuum-secondary carburetor is a good match for this cam on a street 396. You may need to re-jet slightly richer.
  • Carburetor tuning: After a cam swap, idle mixture screws and idle speed need adjustment. Expect to need a vacuum gauge and a timing light.
  • Ignition timing: Increase initial timing to around 14-16° BTDC, and ensure total timing is around 34-36° by 3000 RPM. This helps the cam’s overlap region.
  • Cooling: A cam adds heat. Make sure your cooling system is up to the task – a high-flow water pump and a big radiator are good investments.

Also, be prepared for a change in fuel requirements. With increased compression and more aggressive timing, you may need to run premium unleaded (93 octane). Buy a case of octane booster for peace of mind on hot days.

For tuning tips, OnAllCylinders offers a solid guide to timing and carb settings.

Long-Term Reliability and Maintenance

I’ve put about 5,000 miles on the engine since the cam swap. The Summit Racing kit has proven reliable. The flat-tappet cam requires frequent oil changes with high-ZDDP oil. I change oil every 3,000 miles and use a zinc additive with each change. Check valve lash (preload) occasionally – hydraulic lifters can settle over time. The valve springs should be replaced if you ever rev the engine past the cam’s intended range or install a hotter cam later.

One tip: use a magnetic drain plug and inspect for metal particles. The first oil change after break-in is critical. Mine had only a few tiny specks, which is normal. After that, the oil has remained clean.

Conclusion: Worth Every Dollar

Upgrading my Chevy Big Block 396 with the Summit Racing Cam Kit was one of the best decisions I’ve made for my muscle car. The $1,500 investment delivered a 65-horsepower gain, improved throttle response, and that beautiful aggressive idle. The kit was complete, well-made, and straightforward to install with careful preparation.

If you’re on the fence about camshaft upgrades, my advice is to do it. Plan your supporting mods, take your time during installation, and respect the break-in procedure. The reward is a 396 that feels like a completely different engine – stronger, more responsive, and more exciting to drive.

For anyone looking to source their own kit, check out the Summit Racing Cam Kit K6401. And if you’re restoring a 396-powered Chevelle or Corvette, this engine history guide from Chevy DIY provides useful context.

Remember: the joy of a big-block Chevy lies not just in its numbers, but in the visceral experience. A cam swap will make you fall in love with your car all over again.