Reinforced valve spring kit BMW M20B25

€1,033.08 (tax incl.)

Kit of 12 reinforced valve springs for the 2.5 litre BMW M20B25 engine.

Brand: SUPERTECH
Engines: M20B25 2.5 12v (325i and 325iX E30, 525i E34, Z1)
Springs: double
Contents: springs, upper retainers and lower spring seats

BMW M20B25 engine covered

This kit is for the M20B25, the 2.5 litre inline six with 12 valves and a single overhead camshaft. Its valves are driven by rocker arms with an eccentric adjuster. It sits under the bonnet of the BMW 325i and 325iX E30, the 525i E34 and the Z1.

The kit replaces the standard spring, its upper retainer and its lower spring seat; the original collets are kept.

SUPERTECH reinforced valve spring kit

Beyond the cam lobe's peak, the spring has to call the valve back to its seat and keep it shut. When revs climb, the valve lags behind: with too weak a spring it rebounds, shuts late, then risks striking the piston. This behaviour is called valve float.

Double springs: 396 N at 35.5 mm (89 lbs), 854 N at 10 mm lift, maximum lift 14.8 mm.

Valve spring kit technical specification

Part number	Brand	Springs	Outer / inner Ø	Seat pressure	Open pressure	Rate	Max lift	Kit contents
SPRK-H1005D-M20	SUPERTECH	Double	Outer 29.7 / 20.5 mm Inner 21.9 / 15.5 mm	396 N at 35.5 mm	854 N at 10 mm	51.2 N/mm	14.8 mm	12 springs, 12 titanium upper retainers, 12 lower spring seats

Valve spring kit fitting details

Part	BMW original	Reinforced spring kit
Spring	11 34 1 706 583 + 11 34 1 706 584	Kit specific: SPR-H1005D (double)
Retainer	11 34 1 706 626	Kit specific: RET-H70/T1, titanium
Spring seat	11 34 1 706 609	Kit specific: SEAT-H1002D-M20
Collets	11 34 1 307 136	Original retained

The SUPERTECH kit contains 12 SPR-H1005D double springs, 12 RET-H70/T1 titanium upper retainers and 12 SEAT-H1002D-M20 lower spring seats; the original collets stay fitted.

Measure installed height with the valve closed, from the lower spring seat where the spring rests up to the upper retainer. A quoted load holds only at this figure, 35.5 mm for this kit. Should it grow, for instance once the head face is machined, the load drops by one spring rate per extra millimetre. The table below gives this height and this load.

	SUPERTECH
Installed height	35.5 mm
Seat pressure at this height	396 N

Technical guide

Our brands

SUPERTECH is a Californian company supplying valvetrain parts to competition teams, with a long record of more than thirty years. Springs leave the plant only after ultrasound, X-ray and laser passes, so a hidden internal flaw cannot slip into a delivery.

How to choose

More force on the spring and the valve follows the cam faithfully instead of lifting away from it: the limiter can climb, the camshaft can turn sharper, a turbo can join in without the valves floating. The kit gives 396 N on the seat at 35.5 mm, the figure in the previous table. One safeguard only: your camshaft lift has to remain under the kit's maximum lift, 14.8 mm.

Criterion	Key point
Choosing the pressure	The figure in pounds, 89, names the load applied at the seat; the table converts it to newtons. To decide, weigh three things: camshaft lift, the revs you are after and any boost. Each increase calls for more load, without passing the kit's maximum lift. Ask for no more than needed: a spring that is too stiff wears cams and rockers faster.
Single or double spring	The kit relies on a double spring, two springs set one inside the other that spread the effort and cancel each other's oscillations; the original equipment also has two springs on each valve. Upper retainers and lower spring seats come with the kit, one of each per valve.

When reinforced springs become necessary

Camshaft lifting higher than standard
Peak rpm you wish to raise
Turbo added to a naturally aspirated engine
Head rebuilt for circuit or rally
Tired springs or valve float below the limiter

Compatible vehicles

Model	Engine code	Power	Years
BMW 325i (E30)	M20B25	170-171 hp	1983-1991
BMW 325i Touring (E30)	M20B25	170 hp	1987-1993
BMW 325i Convertible (E30)	M20B25	170-171 hp	1985-1993
BMW 325iX (E30)	M20B25	170-171 hp	1986-1991
BMW 325iX Touring (E30)	M20B25	170 hp	1988-1993
BMW 525i (E34)	M20B25	170 hp	1988-1990
BMW Z1 2.5	M20B25	170 hp	1988-1991