Reinforced valve spring kit BMW M50B25TU M52 M54

BMW engines covered

The BMW M50 in its VANOS variable valve timing version (M50B20TU and M50B25TU, from September 1992), followed by the M52 (2.0, 2.5 and 2.8 litre), the M52TU and the M54 (2.2, 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 valve is closed by a single spring, BMW part number 11 34 7 504 268, sitting on a spring seat 11 34 1 735 254 and held by a retainer and 3-groove valve keepers. On the M52TU, CATCAMS measures a load of 25 kg (245 N) on the seat and 60 kg (588 N) at 10 mm lift for this spring: a value designed for the stock camshaft and rev range.

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.

A reinforced kit increases spring load to keep the valve under control. Compared with the original spring (245 N on the seat, 588 N at 10 mm lift), the CATCAMS kit reaches 343 N on the seat, 40% more, and the SUPERTECH dual spring kits reach 418 N on the seat and 930 N at 10 mm lift, 70% and 58% more. The SUPERTECH and FERREA kits combine alloy steel dual 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

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

Valve spring kit fitting

A spring only delivers its stated load at one precise height: the installed height, the distance between the spring seat and the retainer with the valve closed. Manufacturers set it at 37.5 mm for CATCAMS, 35.7 mm for SUPERTECH and 36 mm for FERREA. If the actual height differs, for example after the valve seats have been recut, the load changes: with a rate of 51.2 N/mm, 1 mm less adds about 51 N. The engine builder therefore measures this height on the cylinder head, with valve, retainer and keepers in place, and corrects it if needed with a shim under the spring.

The camshaft lift must remain below the maximum spring lift: 13.5 mm for the SUPERTECH 67 lbs kit, 12.7 mm for the 80 lbs, 12.5 mm for the 94 lbs and 14 mm for the FERREA kit.

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.
	CATCAMS is a Belgian manufacturer of camshafts and valvetrain parts with a strong racing record: its camshafts have raced in the BTCC and at the 24 Hours of Le Mans.

How to choose

The 67, 80 and 94 lbs values of the SUPERTECH kits are the spring load on the seat, valve closed, expressed in pounds: 298, 356 and 418 N. The higher it is, the better the valve stays closed against boost pressure and follows the cam at high rpm. In return, the allowable lift drops (13.5, 12.7 then 12.5 mm) and cam and tappet wear increases: choose the lowest load that suits the camshaft fitted and the use of the engine.

The CATCAMS single spring keeps the original layout. SUPERTECH and FERREA dual springs combine two nested springs that share the load and damp each other's vibrations: they are designed for more aggressive camshafts, high rpm and forced induction.

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); 11 34 1 403 709 (S50B30US, S52B32US)

Don't forget the valves

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