Supertech K/F-Series Dual Valve Spring Kit

The Supertech SPRK-H1021D Dual Valve Spring Kit eliminates that risk. The dual-spring design produces 95 lbs of seat pressure at 40.4mm installed height and 261 lbs of open pressure at 12mm — numbers that will handle aggressive aftermarket cam profiles without complaint. The spring rate of 13.2 lbs/mm is matched specifically to the K and F-series head geometry, so you're not guessing at compatibility. Max lift is rated to 15.3mm, and coil bind doesn't occur until 22.7mm, giving you real working clearance above that.

The springs themselves are wound from Super Clean Chrome Silicon Vanadium Steel Alloy — not standard wire. This material is chosen specifically because it handles high-cycle fatigue stress without losing its shape. Your spring rate at 50,000 miles should be the same as it was at install. That consistency matters when your build depends on precise valve timing across an entire rev range.

Each kit ships with 16 dual valve springs (SPR-H1021D), 16 titanium retainers (RET-K20A2/T2), and 16 seat locators (SEAT-H1020DS) — everything you need for a complete 4-cylinder head. The titanium retainers are the detail that separates this kit from budget alternatives. Titanium is roughly 40% lighter than steel, which reduces valvetrain reciprocating mass. Less mass means your valves can follow the cam lobe more accurately at high RPM without needing even higher spring pressure to compensate. It's a system-level solution, not just a spring upgrade.

This kit is a strong match if you're running a cam with up to 15.3mm of lift and targeting a high-RPM street or track build. It works well with bolt-in aftermarket cams as well as more aggressive profiles on built engines. If you're unsure whether your cam lift falls within spec, check your cam card against the 15.3mm max lift and 22.7mm coil bind clearance before ordering.

What is the difference between the SPRK-H1021D and SPRK-H1019D?
The H1021D is designed for Honda K-series and F-series engines and includes titanium retainers sized for the K20/K24 and F20C/F22C head. The H1019D targets a different engine family. If you're building a K or F-series application, the H1021D is the correct kit.

Will this spring kit work with aftermarket camshafts?
Yes — as long as your cam's lift doesn't exceed 15.3mm. The SPRK-H1021D handles both mild performance cams and more aggressive aftermarket profiles. Always verify lift spec against coil bind clearance (22.7mm) before finalizing your cam selection.

Do I need to resurface my retainer seats when installing this kit?
Supertech recommends checking and cleaning your retainer seats during any spring swap. If your head has high mileage or shows wear at the seat contact area, a light cleanup will help the seat locators seat evenly and give you accurate installed height for the 95 lb seat pressure spec.

What cam lift range is the SPRK-H1021D designed for?
This kit is rated to a maximum lift of 15.3mm with coil bind occurring at 22.7mm. It suits a wide range of street and track cam profiles built around K20, K24, F20C, and F22C heads.