Reinforced intake valves BMW M50B25TU M52B25 M52B28 M54B25 M54B30

BMW engines covered

The BMW M50 in its VANOS variable valve timing version (M50B25TU, from September 1992), followed by the M52 (2.5 and 2.8 litre), the M52TU and the M54 (2.5 and 3.0 litre) are the 24-valve inline six-cylinder petrol engines fitted to the 3 Series (E36 and E46), 5 Series (E34, E39 and E60), 7 Series (E38 and E65), Z3, Z4, X3 and X5. The E36 M3 built for the North American market (S50B30US then S52B32US) use the same cylinder head.

Each engine is fitted with 12 intake valves with a 6 mm stem, BMW part number 11 34 1 739 822 (11 34 1 438 385 on the M54, same dimensions): 33.0 mm head, 6.0 mm stem, 106.1 mm length, held by 3-groove valve keepers. Designed for stock power, they are put to the test as soon as a build increases valve lift, spring rate, engine speed or cylinder pressure.

SUPERTECH and FERREA reinforced intake valves

The intake valve opens and closes the path for fresh charge dozens of times per second at high rpm. Each time it closes, its head strikes the cylinder head seat, and its stem slides constantly in the guide. It runs between 400 and 550 °C, a range in which the chrome-silicon steel of the original valve already loses strength: 500 MPa at 500 °C, then 250 MPa from 600 °C, just above this range, half as much. The higher the lift, spring stiffness, engine speed and boost pressure, the more these impacts, this friction and this heat fatigue the valve.

SUPERTECH valves are forged from an enhanced EV8 (21-4N) steel, a race-grade chrome-nickel stainless steel that retains 650 MPa at 500 °C, 30% more, and 550 MPa at 600 °C, more than double the original steel. FERREA valves come from its Competition Plus series, for which the manufacturer states 20% higher hot strength and fatigue resistance, and 25% longer seat life. Two finishes are available for these engines: SUPERTECH black nitrided stainless steel, whose harder and smoother surface reduces friction and wear, and FERREA hard chrome stems.

Intake valve technical specifications

FERREA: F1550P*12 and F1551P*12 not listed by the manufacturer for the S52B32US.

Valve fitting

The number of grooves on the valve and on the keepers must match: SUPERTECH specifies KPR-VW6-T keepers for its 3-groove valves and KPR-6S-7 keepers for its single-groove valves. A single-groove valve must never be fitted with the original keepers.

The +1 mm size increases the head diameter: it is fitted to a cylinder head whose seats have been machined to this size, a workshop job to plan alongside the cylinder head rebuild.

Technical guide

Our brands

	SUPERTECH, based in San Jose, California, has been designing valves and valvetrain parts for racing for more than 30 years, from drag racing to rally and circuit racing.
	FERREA Racing Components, founded by Argentinian engine builders and based in Fort Lauderdale, Florida since 1978, manufactures valvetrain parts for NASCAR, drag racing and road racing.

Standard size or +1 mm?

The standard size is fitted to a cylinder head whose seats are still at factory size. The +1 mm size is used when the seats need recutting: recutting widens the seat, and a larger head restores correct seat contact while increasing the flow area.

Single groove or 3 grooves?

3-groove valves keep the BMW design: their keepers do not clamp the stem, so the valve rotates and limits carbon build-up on its seat. This is the right choice for a road engine. On single-groove valves, the keepers clamp the stem tightly above and below the groove, which only locates them: the valve stays firmly held at high rpm and under high spring load, which is why they suit competition use. They are fitted with KPR-6S-7 keepers, 3-groove valves with the original keepers or KPR-VW6-T keepers.

When reinforced valves become necessary

• Camshafts with higher lift or stiffer valve springs
• Raised rev limit
• Turbocharger or supercharger added
• Cylinder head rebuild on a circuit, drift or rally engine
• Original valves marked, worn or already at repair size

Vehicle compatibility

OEM part number (intake valve): 11 34 1 739 822; 11 34 1 438 385 (M54B25, M54B30)

Don't forget the exhaust valves

A rebuilt cylinder head is fitted with new intake and exhaust valves, and with new valve stem seals. We offer the matching parts for these engines: