4R300 Rally Cylinder Head MINI R53 | R52 | R50 | Cooper | Cooper S | JCW

COMPETITION-BUILT
The 4R300 Rally Head is developed for competition-built MINIs that operate far beyond the limits of the stock cylinder head. Whether you're running high boost, aggressive cam profiles, or extended high-RPM sessions on track, this head is engineered to meet the demands of professional motorsport use. With significantly improved airflow and reinforced valvetrain stability, it supports engine speeds of up to 7600 RPM, delivering the performance and durability required to stay competitive under extreme conditions.

READY TO PERFORM
Before machining, all cylinder head castings are fully disassembled and meticulously cleaned to remove any residual oil, carbon buildup, or debris from previous use. Each casting then undergoes pressure testing and visual inspection to verify it is free from cracks, warped surfaces, damaged threads, or other potential defects. Only heads that meet our quality standards proceed to the machining stage.

MACHINED TO LAST
The machining process begins with replacing all valve guides with our specially designed manganese bronze Ultraflow guides, engineered for optimal heat transfer and shaped to improve airflow without compromising valve support. Once installed, each guide is precision-honed to achieve the correct valve-to-guide clearance, ensuring proper stem lubrication and long-term reliability at high RPM. The head is then fixtured in our in-house Serdi valve seat machine, where all seats are cut using a custom multi-angle profile optimized for the flow characteristics of oversized SUPERTECH 32 mm intake and 25.2 mm exhaust valves. After seat cutting, the deck surface is resurfaced to achieve maximum flatness and the ideal finish for a reliable seal with the MLS head gasket. Finally, the cylinder head undergoes a thorough cleaning to remove any residual debris or oil from the machining process, preparing it for final assembly.

BUILT TO WITHSTAND
All 4R300 cylinder heads are assembled using high-performance SUPERTECH valvetrain components, including oversized 32 mm (+1.8 mm) intake valves and 25.2 mm (+2.3 mm) exhaust valves. Beehive valve springs with lightweight titanium retainers and single-groove keepers ensure stable valve control under high-RPM and high-load conditions. Viton valve stem seals are used to provide long-lasting oil control and reliability. Combined with our custom multi-angle valve job, the valvetrain is built for maximum performance and durability on track.

WHAT MAKES PORTING BETTER?
Cylinder head porting is a proven method to improve the airflow efficiency of the cylinder head. At 4RevisionEngines, we carefully reshape the ports to maximize flow while maintaining critical air velocity, focusing on flow quality, not just port size. All porting work is developed and verified in-house using our flow bench to ensure consistent, measurable gains in cylinder head performance.

THE CHAMBER MODIFICATION
All 4R300 cylinder heads feature reshaped combustion chambers as part of the porting process. This refinement removes sharp edges and casting irregularities that could create hot spots, reducing the risk of detonation and pre-ignition under high load. The area around the valves is also smoothed and blended to eliminate flow disruptions, improving low-lift flow and overall combustion efficiency.

OPTIONAL CAMSHAFTS
If you're targeting more power from your 4R300 head package, upgrading the camshaft is essential. We offer several camshaft options to suit different setups. For improved low-end torque and drivability, we recommend the CatCams 1302461. For increased high-RPM performance and maximum top-end power, the CatCams 1302469 is the ideal choice. Both profiles provide noticeable gains in power and torque across the entire RPM range.

CYLINDER HEAD INSTALLATION PACKAGE
Simplify your cylinder head installation by adding our Head Installation Package to your order. To ensure maximum performance and reliability from your 4RevisionEngines build, we supply only high-quality components that protect your investment. Each kit includes the correct fluids, a complete set of gaskets, head bolts, and a fresh set of spark plugs, everything required for a clean and efficient install. Compatible with all MINI Gen 1 engines, this package offers the essential parts at a discounted rate, saving you time, cost, and unnecessary hassle.

POWER RATING
The 4R300 cylinder head is engineered to support power outputs of up to 300 BHP when paired with the appropriate supporting modifications, such as larger superchargers, larger injectors, improved intercooling, colder intake air, and high-flow exhaust systems.

WHAT’S IN IT

Cylinder Head – OEM casting, machined and ported
Intake Valves – SUPERTECH +1.8 mm (32.0 mm) oversized valves
Exhaust Valves – SUPERTECH +2.3 mm (25.2 mm) oversized valves
Valve Springs & Retainers – SUPERTECH performance spring kit with lightweight titanium retainers
Valve Locks – SUPERTECH single-groove collets
Valve Guides – 4REVISION Ultraflow manganese-bronze guides
Valve Stem Seals – Viton high-performance seals
Valve Job – Multi-angle valve job
Deck Surface – Resurfaced for MLS gasket compatibility
Cleaning – Professionally cleaned and prepared for final assembly