Genuine Mazda Exhaust Valve • BP6F-12-121

Genuine Mazda BP6F-12-121 Exhaust Valve

Replacement Genuine Mazda exhaust valve for Mazda MX-5 Mk2.5 / NB facelift models fitted with the 1.8L BP-Z3 VVT petrol engine from 2002 to 2005 listed in the compatibility table.

The exhaust valve is located within the cylinder head and controls the flow of burned combustion gases from the combustion chamber into the exhaust port. It operates through the camshaft, valve lifter, valve spring, upper retainer and collet assembly.

During engine operation, the valve repeatedly opens against combustion pressure and closes against the machined valve seat. Because exhaust valves are directly exposed to hot combustion gases, their material specification, stem dimensions and sealing-face geometry are critical to reliable engine operation.

This listing supplies one Genuine Mazda exhaust valve. The BP-Z3 engine uses eight exhaust valves, so eight are required when replacing the complete exhaust-valve set. Inlet and exhaust valves are different components and must not be interchanged.

Replacement may be required where the original valve is burned, bent, cracked, pitted, excessively worn or no longer seals correctly against the valve seat. Possible symptoms include low compression, misfiring, reduced engine power, poor idle quality, increased emissions or leakage identified during cylinder-head testing.

• Part type: Exhaust valve
• Primary use: Controls exhaust-gas flow from the combustion chamber into the exhaust port
• Location: Cylinder head / exhaust side of the valvetrain
• Engine application: Mazda MX-5 Mk2.5 1.8L BP-Z3 VVT petrol engine
• Quantity per cylinder: Two exhaust valves
• Quantity per engine: Eight exhaust valves
• Quantity supplied: One exhaust valve
• Brand: Genuine Mazda
• Part No.: BP6F-12-121
• Also referenced as: BP6F12121
• Associated Mazda references: BP4W-10-100 and BP6D-10-100
• Fitment distinction: Intended for the confirmed facelift 1.8L VVT application shown in the compatibility table
• Important note: The inlet and exhaust valves are separate components and are not interchangeable

Fitment advice: Confirm that the engine is the facelift 1.8L BP-Z3 VVT unit and compare the original valve dimensions and cylinder-head application before assembly. Any cylinder head that has previously been rebuilt with non-standard valves, guides or seats should be measured carefully before ordering replacement components.

Other items to consider: When changing this part, you may also want to consider purchasing valve stem oil seals, valve guides, valve springs, upper spring retainers, valve collets, hydraulic or mechanical adjustment components, a cam-cover gasket, cylinder-head gasket, head bolts, timing belt and tensioner components.

Useful tools / consumables: Valve spring compressor, valve-guide measuring equipment, micrometer, dial gauge, valve-seat testing equipment, valve-lapping tools where appropriate, clean assembly lubricant, calibrated torque wrench and the correct Mazda-compatible camshaft and timing tools.

Difficulty guide: DIY Difficulty: Advanced / Engine Reconditioning. Replacement requires cylinder-head and valvetrain dismantling. Valve-guide clearance, valve-seat contact, installed height and sealing must be measured and corrected as necessary before the engine is reassembled.

Why Genuine Mazda? Genuine Mazda exhaust valves are manufactured to the intended stem diameter, overall length, head profile, seat angle, material specification and heat-resistance requirements. Using the correct OE valve helps retain reliable sealing, correct valvetrain geometry and compatibility with the original Mazda valve guide, seat, spring and retaining components.

What’s in the box: One Genuine Mazda exhaust valve, part number BP6F-12-121. Valve stem seal, spring, retainer, collets and other cylinder-head components are not included.

Installation notes: Inspect and measure the valve guide, valve seat and adjoining valvetrain components before installation. Confirm the valve seating pattern and valve-to-guide clearance, and carry out any required cylinder-head machining using suitable specialist equipment. Lubricate the valve stem during assembly, install a new valve stem seal and follow the applicable Mazda workshop procedure for camshaft timing, valve-clearance checks and cylinder-head assembly.