Forged for Performance: EC 72mm Piston & Rod Upgrade for Wildcat 240

In most Road to Horsepower videos, the upgrades tend to focus on displacement, cylinder heads, camshafts, or carburetors. But there's one critical component that often goes overlooked: the piston. Until now, the only racing-style piston featured has been the Tillotson 72mm Hypereutectic piston—designed by EC Carburetors—a proven, budget-friendly option used in high-revving small engines since 2019.

But to push the limits further, EC Carburetors has developed a new forged 72mm piston with moly-coated skirts—a high-performance upgrade designed specifically for the Wildcat 240. Paired with a longer billet connecting rod, this combo aims to reduce reciprocating mass, increase durability, and improve efficiency across the RPM range.

Why Upgrade the Piston and Rod?

1. Forged Piston Advantages

The new EC 72mm piston differs from the previous cast version in several key ways:

• Forged Construction: Offers significantly greater strength and fatigue resistance.
• Moly-Coated Skirts: Reduce friction, wear, and heat generation.
• Thinner, Low-Tension Rings: Lower drag, improve ring seal, and reduce surface friction.
• Shorter Compression Height: Allows for:
• Longer Connecting Rods, which improve rod ratio and reduce angular loading.
• Better High-RPM Stability, as the pin sits closer to the piston crown.
• Increased Stroke Potential in limited deck height applications without risking piston-to-head or crankshaft counterweight interference.

Benefits of Longer Rods

The piston’s shorter compression height allows the use of a longer connecting rod, which brings several engineering benefits:

• Improved Rod Angle: Reduces side loading on cylinder walls, leading to lower wear and friction.
• Slower Piston Speed at TDC: Minimizes mechanical stress during the most vulnerable phase of combustion.
• Improved Engine Efficiency: The piston spends more time near TDC (longer dwell), aiding combustion stability.
• Reduced Risk of Stretch-Related Interference: A longer rod stretches less under load, lowering the chance of piston-to-valve or piston-to-head contact.

Rotating Assembly Balance and Vibration Reduction

Balancing a single-cylinder engine is inherently challenging. True internal balance requires a countershaft, which our small engines lack. Instead, manufacturers typically rely on heavy cast iron flywheels to dampen vibrations. But when switching to a lightweight aluminum flywheel, vibration increases—despite gains in throttle response and acceleration from reduced inertia.

The traditional approach is to add tungsten or Mallory metal to the crankshaft for partial internal balancing. However, reducing the mass of the piston and rod is another effective strategy. A lighter reciprocating assembly is easier to balance, reduces crankshaft loading, and leads to smoother engine operation.

Even though a single-cylinder engine can’t be fully balanced internally, the benefits of weight reduction—especially in reciprocating parts—are clear during both dyno testing and real-world riding.

Stage 4 Build Update: Only One Major Change

For this update, we kept the same Stage 4 Wildcat 240 build from our previous test. The camshaft, head, carburetor, and ignition remain unchanged. The only modifications are:

• New EC Forged 72mm Piston
• New Billet 3.59” Connecting Rod

This simple swap dramatically changes the dynamics of the engine without increasing displacement or compression.

Component Comparison

Piston Comparison (Complete Assembly)

Result: Switching from the stock Wildcat piston to the EC forged piston saves approximately 56g, or over 25% reduction in reciprocating mass.

Connecting Rod Comparison

Although the new rod is slightly heavier overall due to bearing weight, the big-end weight improves durability, and the combination is still lighter than stock when paired with the EC piston.

Combined Rod + Piston Assembly Comparison

The new combo reduces weight by 44.5g over stock and 59g lighter than the previous Stage 4 build—critical for high-RPM reliability and performance.

Dyno Results

Gain: +0.24 ft-lbs torque and +0.23 HP—without any tuning changes.

While the peak gains may appear modest, the real improvements come in engine feel and reliability:

• Smoother operation with less vibration
• Better throttle response
• Lower long-term component wear
• Improved power delivery throughout the rev range

Conclusion: Subtle Changes, Major Impact

Upgrading to a forged piston and longer billet rod may not grab headlines like a bigger cam or larger carburetor, but it’s one of the most fundamental improvements you can make to a high-performance small engine.

Whether you're racing on the track or carving trails on your mini bike or kart, this setup will deliver:

• Better durability
• Lower vibration
• Smoother revs
• Greater high-RPM stability

If you're chasing every last ounce of performance and reliability, the EC Forged 72mm Piston and Billet Rod combo is a game-changer.