SUPERTECH bronze valve guides BMW M3 E30 S14B23 S14B25

BMW engines concerned

The guides in this kit fit the 16-valve, 7 mm stem cylinder head of the BMW S14 four-cylinder: the 2.3 litre S14B23 of the E30 M3, in saloon, convertible and Evolution form, and the 2.5 litre S14B25 of the M3 Sport Evolution.

Each of the 16 valves slides in a guide pressed into the cylinder head. BMW specifies a bore of 7.0 mm and an outside diameter of 12.00 mm for these guides, with two repair sizes on the outside diameter: 12.20 and 12.40 mm.

SUPERTECH manganese bronze valve guides

The guide keeps the valve aligned with its seat, passes part of the heat taken up by the stem to the cylinder head and supports the stem seal. Once worn, it lets the valve develop play: the valve seats badly, oil runs down its stem, and the result is oil consumption, blue smoke and falling compression.

SUPERTECH machines these guides precisely from manganese bronze, a copper-based alloy which, according to the brand, carries heat away far more effectively than the sintered guides fitted as standard by car makers. As a rule, they go together with a set of reinforced valves. Each kit holds the 16 guides of one cylinder head: a single part number covers inlet and exhaust alike.

Valve guide technical specifications

Valve guide installation

Technical guide

For these engines, we offer reinforced valves with a 7 mm stem:

Our brand

Based in San Jose, California, SUPERTECH has been making valves, springs, retainers and guides for racing engines for three decades. Its parts are designed with finite element analysis, checked by ultrasound, X-ray and laser, then developed with engine builders in drag racing, rallying and circuit racing.

Standard or oversize?

SUPERTECH supplies this guide in standard size, 12.03 mm outside diameter, and in a 0.0013" oversize, i.e. 12.065 mm.

Manganese bronze

Made of copper and zinc with manganese, aluminium and iron, this bronze combines high mechanical strength with good resistance to wear and corrosion; it is used for bushes and guiding parts under heavy load in service.

When valve guides must be replaced

• Oil burnt past the valve stems
• Reinforced valves going into a tired cylinder head
• Cylinder head rebuild for track, drift or rally use
• Full valvetrain overhaul

Vehicle compatibility

Remember the valve stem seals

Changing the guides means fitting new valve stem seals at the same time. Here are the SUPERTECH seals that suit these engines: