For an MGB enthusiast (for instance) roller rockers are often one of those "while you're in there" motor upgrades, but they actually deliver tangible mechanical benefits.
On an MGB’s 1.8L B-Series engine, the stock rocker arm is a simple forged steel or cast piece that slides across the tip of the valve stem (see worn tip in the purple circle).
What is the MAJOR drawback of the stock rocker arm? Destructive Side-Loading.
The valve stem is held in place by a valve guide (usually made of cast iron or bronze). This guide is designed to handle vertical motion, not horizontal pressure. Constant side-loading leads to several critical issues:
1. "Hourglassing" the Valve Guides
Over time, that constant lateral pressure wears the top and bottom of the valve guide into an "hourglass" shape. Once the guide is wallowed out, the valve no longer sits perfectly centered on the valve seat. The Result: A poor seal, leading to loss of compression and "burned" valves.
2. Oil Consumption & Blue Smoke
Your valve stem seals rely on the valve moving perfectly straight. When side-loading causes the valve to wobble or lean, it creates a gap that allows oil to be sucked down past the seal and into the combustion chamber. The Result: High oil consumption and that classic puff of blue smoke on startup or deceleration.
3. Increased Stem Heat
Friction creates heat. When the stem is constantly "scrubbing" against the guide due to side-loading, it generates localized heat that can't be easily dissipated. The Result: In extreme cases, this can lead to valve seizing or the stem becoming brittle and snapping, which usually results in catastrophic engine failure.
What is a roller rocker?
The Roller Rocker replaces the standard solid-tip rocker arm. It features a small roller bearing at the tip (where it contacts the valve) and needle bearings at the fulcrum (the center pivot).
Why upgrade to Roller Rockers?
A roller rocker replaces the "scrubbing" flat tip with a bearing-supported wheel.
- True Vertical Pressure: As the rocker moves through its arc, the wheel rolls across the valve tip. This allows the lateral movement of the rocker arm to be absorbed by the rotation of the roller rather than being transferred as a "shove" to the valve stem.
- Centering: By eliminating that shove, the valve stays perfectly centered in its guide, ensuring the valve face hits the seat squarely every single time.
Other benefits?
Increased Effective Lift: Staying with the MGB example, the standard ratio for the Classic Car Performance roller rockers is 1.5:1 (also available in more aggressive ratios), compared to the stock ratio of approximately 1.45:1. This opens the valves further without needing a cam change. Opening the valve more—referred to as increased lift—is essentially like widening a straw, allowing the engine to take a "deeper breath". For engines of the 1950's, 60's, and 70's, like the MGB’s B-Series, those cast iron heads are "breath-restricted" in stock form. This simple upgrade has a noticable impact on performance.
Why is that extra lift from a high-ratio roller rocker is so beneficial?
1. Improved Volumetric Efficiency
The primary benefit is airflow. By pushing the valve further into the combustion chamber, you create a larger curtain area for air and fuel to enter (and exhaust gases to exit). The Result: The cylinders fill more completely on every intake stroke, which directly translates to more torque and horsepower.
2. Higher Average Lift
Even though a roller rocker doesn't change the duration (how long the valve stays open) of your camshaft, it changes the area under the curve. Because the rocker ratio is higher, the valve reaches any given opening point faster and stays "near" full lift longer. This allows for significantly more airflow throughout the entire cycle, not just at the very peak.
3. Compensating for Port Restrictions
The cast iron heads often have "pockets" or restrictions just behind the valve seat. Opening the valve further moves the valve head away from these restrictive areas, allowing the air to tumble into the cylinder with less turbulence.
4. "The Bolt-On Cam" Effect
For many owners, swaping a camshaft is a massive undertaking. Higher-ratio roller rockers give you many of the benefits of a performance cam—specifically the increased lift—without having to tear down the front of the engine or timing gear.
Summary of Benefits:
- Top-End Power: The engine won't "run out of breath" as early in the RPM range.
- Throttle Response: More air moving more quickly makes the engine feel more "snappy" when you blip the throttle.
- Efficiency: Better exhaust scavenging means fewer burnt gases remain in the chamber to dilute the next fresh intake charge.
- Valvetrain Longevity: By reducing the side-force on the valve stems, you extend the life of the head, especially in high-RPM or performance-street applications.
- Stability: Our rockers are made from high-grade aluminum which flexes less than stock arms at high RPM, keeping your timing more accurate.
