MG published a Special Tuning booklet for the MGB which described seven stages of tune, ranging from basic cylinder head polishing through to full competition specification with larger carburettors, high-lift camshafts, and overbored pistons. That graduated approach, where each stage built upon the last, remains a sound framework for tuning the B-series engine today, and the components available reflect that philosophy.
Stage II Cylinder Heads
The cylinder head is the single most effective area to address. A Stage II head, polished and ported to improve gas flow, fitted with new valves, valve springs, and bronze valve guides alongside hardened exhaust valve seats, transforms the engine’s breathing and delivers a significant increase in both mid-range torque and top-end power. Stage II heads are available for both chrome bumper in-line oil feed and rubber bumper offset oil feed configurations.
Camshaft & Valve Train
The camshaft determines the engine’s character. Mild road camshafts offer a broader spread of torque and retain a smooth idle suited to everyday driving, while fast road profiles extend the power band higher into the rev range at the expense of some low-speed tractability. Cam kits are available for all engine types and include valve springs, cam followers, cam lube, and a static timing disc. Roller rocker assemblies replace the standard pressed steel rockers with precision roller-tipped items, reducing friction at the valve interface and improving valve clearance adjustment.
They are available in standard and high-lift ratio options, and in both in-line and offset feed configurations. High-lift rockers must be paired with the correct combination of valves, springs, and camshaft to avoid valve-to-piston interference.
Vernier Timing Gear
A duplex vernier timing gear set allows the camshaft timing to be set in one-degree increments rather than to the nearest tooth, enabling precise optimisation for a specific engine build. The duplex chain also offers greater strength and wear resistance than the simplex chain used on later 18V engines. For a comprehensive approach, engine tuning components should be considered alongside fuel system and exhaust upgrades. A Stage II head and performance camshaft deliver their best results when supported by adequate carburettors, a free-flowing exhaust, and correct ignition timing.
Modified engines should ideally be set up on a rolling road. The MGOC Spares performance range covers Stage II cylinder heads, performance camshaft kits, roller rocker assemblies, vernier timing gears, alloy rocker covers, and all associated components.