Reinforced valve spring kit Toyota GT86 Subaru BRZ FA20

€909.00 (tax incl.)

Kits of 16 reinforced valve springs for the Toyota Subaru 4U-GSE FA20 engine.

Brands: FERREA, SUPERTECH
Engines: 4U-GSE / FA20 (GT86, FR-S, BRZ)
Springs: single or double
Contents: springs, upper retainers, lower spring seats depending on the kit

SPRK-100-BRZ

Brand - Type of Springs: SUPERTECH - SPRINGS DOUBLE 87 LBS

On order, 15 to 30 days lead time

The Toyota Subaru 4U-GSE FA20 engine covered

All five kits are aimed at the 2.0 litre, 16-valve flat-four known as the 4U-GSE at Toyota and the FA20 at Subaru, fitted to the Toyota GT86, Scion FR-S and Subaru BRZ built from 2012 to 2015.

For each of the two FERREA kits, the brand asks for the original lower spring seat to be discarded in favour of its own part. The factory spring and upper retainer are replaced too; the original collets stay in place. The three SUPERTECH kits likewise replace the spring and supply their own retainers and seats; the original collets are kept.

FERREA and SUPERTECH reinforced valve spring kit

After the cam, it is the spring that returns the valve to its seat. When engine speed goes beyond what its load allows, the valve floats, comes back late and can touch the piston.

The single-spring KT4021 gives 267 N on the seat at 34.0 mm and 601 N at 10.0 mm of lift. The double-spring KT4022 gives 311 N and 756 N. The three double-spring SUPERTECH kits, fitted at 33.5 mm, give 387 N, 329 N and 445 N on the seat (SPRK-100-BRZ, SPRK-1002-BRZ, SPRK-200-BRZ) and 943 N, 774 N and 988 N at 10.0 mm of lift.

Valve spring kit technical specification

Part number	Brand	Springs	Outer / inner Ø	Seat pressure	Open pressure	Rate	Max lift	Kit contents
KT4021	FERREA	Single	Outer 28.0 mm Inner 20.8 mm	267 N at 34.0 mm	601 N at 10.0 mm	33.3 N/mm	14.5 mm	16 springs, 16 tool steel upper retainers, 16 lower spring seats
KT4022	FERREA	Double	Outer 28.0 / 20.8 mm Inner 20.8 / 16.5 mm	311 N at 34.0 mm	756 N at 10.0 mm	44.5 N/mm	14.5 mm	16 springs, 16 titanium upper retainers, 16 lower spring seats
SPRK-100-BRZ	SUPERTECH	Double	Outer 30.2 / 22.2 mm Inner 22.2 / 16.8 mm	387 N at 33.5 mm	943 N at 10.0 mm	55.6 N/mm	15.0 mm	16 springs, 16 upper retainers, 16 lower spring seats
SPRK-1002-BRZ	SUPERTECH	Double	Outer 29.1 / 20.5 mm Inner 21.9 / 15.5 mm	329 N at 33.5 mm	774 N at 10.0 mm	44.5 N/mm	14.0 mm	16 springs, 16 upper retainers, 16 lower spring seats
SPRK-200-BRZ	SUPERTECH	Double	Outer 30.2 / 22.2 mm Inner 22.2 / 16.8 mm	445 N at 33.5 mm	988 N at 10.0 mm	54.3 N/mm	13.5 mm	16 springs, 16 upper retainers, 16 lower spring seats

Valve spring kit fitting details

Part	Toyota Subaru original	Reinforced spring kit
Spring		Kit specific: S10154 (KT4021, single) or S10155 (KT4022, double); SPR-H100-DR (SPRK-100-BRZ), SPR-H1002D (SPRK-1002-BRZ) or SPR-H200-DR (SPRK-200-BRZ), double
Retainer		Kit specific: E20055 tool steel (KT4021), E11127 titanium (KT4022), RET-H1000-BRZ (SPRK-100-BRZ) or RET-H1000D-BRZ (SPRK-1002-BRZ and SPRK-200-BRZ)
Spring seat		Kit specific: SL1139 (KT4021) or SL1140 (KT4022), original seat discarded; SEAT-H1002D-BRZ (SUPERTECH kits)
Collets		Original ones kept

The KT4021 contains 16 S10154 single springs, 16 E20055 tool steel upper retainers and 16 SL1139 lower spring seats. The KT4022 contains 16 S10155 double springs, 16 E11127 titanium upper retainers and 16 SL1140 lower spring seats. Each SUPERTECH kit contains 16 double springs, 16 upper retainers and 16 lower spring seats: SPR-H100-DR, RET-H1000-BRZ and SEAT-H1002D-BRZ for the SPRK-100-BRZ; SPR-H1002D, RET-H1000D-BRZ and SEAT-H1002D-BRZ for the SPRK-1002-BRZ; SPR-H200-DR, RET-H1000D-BRZ and SEAT-H1002D-BRZ for the SPRK-200-BRZ. The original collets are kept.

Take installed height with the valve shut, from the spring's lower seat contact to its upper contact. The kits are quoted at 34.0 mm (FERREA) and 33.5 mm (SUPERTECH); above it, every added millimetre subtracts one spring rate from the load. Permitted lift (13.5 to 15.0 mm by kit) is in the technical table. Gauge the height on each valve before assembling.

	FERREA	SUPERTECH
Installed height	34.0 mm	33.5 mm
Seat pressure at this height	267 N (KT4021) 311 N (KT4022)	387 N (SPRK-100-BRZ) 329 N (SPRK-1002-BRZ) 445 N (SPRK-200-BRZ)

Technical guide

Our brands

	FERREA was born in 1978 in Florida, founded by Argentine mechanics settled in the United States. It is behind competition springs, valves, tappets and retainers seen in dragsters, stock cars and circuit single-seaters. Its special alloys are proven in racing.
	SUPERTECH, based in California, built its name on competition engines. It supplies springs, retainers and valves for tuned engines, from the track to the road. Every spring is coiled from an alloy steel, then inspected before it ships. Its kits arrive with their retainers and seats.

How to choose

A firmer spring keeps the valve on the cam well past the standard engine speed: you can rev higher, pick a livelier camshaft or add a supercharger without fearing valve float. The single-spring KT4021 brings 267 N on the seat; the double-spring KT4022 brings 311 N; the three double-spring SUPERTECH kits bring from 329 N to 445 N. Camshaft lift must stay under the maximum lift of the kit you pick: 14.5 mm for FERREA, from 13.5 to 15.0 mm for SUPERTECH. Measure it before ordering.

Criterion	Key point
Choosing the pressure	Between the five kits, base your decision on cam lift, the rpm you expect and the boost of any turbo. Rates run from 33.3 to 55.6 N/mm depending on the kit: a stiffer rate lets load build more quickly as the valve opens. Going past the need gains nothing and strains the engine for no gain.
Single or double spring	A single spring has one coil while the double nests a pair, spreading the effort and filtering vibration more effectively. The three SUPERTECH kits all use double springs. FERREA states the titanium retainer weighs 40% less than steel; the KT4021 uses tool steel. Every kit also supplies its lower spring seat.

When reinforced springs become necessary

Camshaft lifting more than stock
Rev limit raised clearly
Supercharger or turbo fitted to this engine
Head reworked for circuit or hill climbs
Worn springs, valves that drop out near the limit

Compatible vehicles

Model	Engine code	Years
Toyota GT86 (ZN6) 2.0	4U-GSE / FA20	2012-2015
Subaru BRZ 2.0	FA20 / 4U-GSE	2012-2015
Scion FR-S 2.0	4U-GSE / FA20	2012-2015

Important: these kits are for the 4U-GSE or FA20 engine of the Toyota GT86, Scion FR-S and Subaru BRZ, from 2012 to 2015. The turbo FA20 engines of other Subaru models are not covered on this page. One kit of 16 fits a complete engine.