Reinforced valve spring kit BMW M50TU M52 M54

BMW engines covered

This kit covers the BMW 24-valve inline six-cylinder petrol engines with a 6 mm valve stem: the M50 in its VANOS versions (M50B20TU and M50B25TU, from September 1992), the M52 in 2.0, 2.5 and 2.8 litre form, the M52TU, then the M54 in 2.2, 2.5 and 3.0 litre form. They are found under the bonnet of the 3 Series E36 and E46, the 5 Series E34, E39 and E60, the 7 Series E38 and E65, as well as the Z3, Z4, X3 and X5.

Each valve is closed by a single spring, BMW part number 11 34 7 504 268 (superseding the original M50TU part 11 34 1 738 488), sitting on a lower spring seat 11 34 1 735 254 and held by an upper retainer and 3-groove valve collets.

CATCAMS, SUPERTECH and FERREA reinforced valve spring kits

The valve spring closes the valve and keeps it in contact with the cam lobe. At high revs, the inertia of the valve increases: if the spring lacks load, the valve no longer follows the cam profile, bounces on its seat and can hit the piston. This is valve float, the first limit of an engine whose rev limit or lift is raised.

Compared with the original spring (about 245 N on the seat and 588 N at 10 mm lift), a reinforced kit raises the seat load by 22 to 71% to keep the valve under control: 343 N for the CATCAMS kit, up to 418 N on the seat and 930 N at 10 mm lift for the SUPERTECH 94 lbs kit. The SUPERTECH and FERREA kits combine double springs with titanium retainers, 40% lighter than a steel retainer according to FERREA: less moving mass for the same load. The CATCAMS kit keeps a single spring and a dedicated retainer, for a reinforcement close to the original assembly.

Valve spring kit technical specifications

Valve spring kit fitting

FERREA KT4041: the S10049 spring requires the E11025 titanium upper retainer and the SL1021 lower spring seat supplied in the kit; the original lower spring seat is discarded.

The installed height is the distance between the lower spring seat and the upper retainer with the valve closed. Each manufacturer states the seat load at its own installed height; if this height increases, for example after the valve seats have been recut, the load drops, for each millimetre, by the value of the spring rate (see the specifications table).

Technical guide

Our brands

	SUPERTECH, based in San Jose, California, has been making competition valvetrain parts for more than 30 years. Its springs are wound from very high purity chrome-silicon-vanadium wire and its retainers machined from military grade titanium, inspected by ultrasound, X-ray and laser.
	FERREA Racing Components, founded in 1978 in Florida by two Argentinian engine builders, Horacio Ferrea and Daniel Urrutia, makes its entire valvetrain in house, from valves to springs, tappets and rocker arms. Its parts race in NASCAR, drag racing and on circuits.
	CATCAMS (Cat Cams N.V.) is a Belgian camshaft and valvetrain manufacturer with a worldwide reputation, equipped with a CNC grinder able to cut inclined cams. Its springs and retainers complement its camshafts, which have raced in the BTCC and at the Le Mans 24 Hours.

How to choose

A reinforced kit keeps the valve in contact with the cam as revs rise: you can raise the rev limit, fit a more aggressive camshaft or a turbo without valve float. At 10 mm lift, the SUPERTECH and FERREA kits deliver 36 to 58% more load than the original spring. The only limit: your camshaft lift must stay below the kit's maximum lift, from 12.5 to 14.0 mm depending on the model.

When reinforced springs become necessary

• Camshafts with higher lift fitted
• Raised rev limit
• Turbocharger or supercharger added
• Cylinder head rebuild on a circuit, drift or rally engine
• Tired original springs or valve float observed at high revs

Vehicle compatibility

OEM part number (valve spring): 11 34 7 504 268 (M50TU, M52, M52TU, M54; supersedes 11 34 1 738 488 on the M50TU); 11 34 1 403 709 (S50B30US, S52B32US)

Don't forget the valves

A cylinder head rebuilt with reinforced springs is best fitted with new inlet and exhaust valves. We offer the matching valves for these engines: