2011-17 5.0 Coyote MMR Upgraded Valve Spring & Retainer kit

Direct replacement and upgrade for 5.0 Coyote Mustang Boss and std GT models

Designed for boosted applications and any Highr RPM n/a applications. Compatible and ANY cam on the market up to .550 lift (if your cam has higher lift please see MMR Gen 2 Valve spring kit part# 400888). This is the only spring on the market tested beyond 2000RWHP and 10000RPM!! Includes 32 springs and Chromoly retainers. Works with all Valves, seals and valve locks. Cam Limiters or MMR Phaser Deletes recommended. Beware of kits that sell springs only, the higher pressure springs will break the factory retainers eventually and cause engine failure!!

Track tested by team MMR! As used by: 2014 NMRA Coyote Modified Champion 2015 NMRA Coyote Modified Champion 2015 NMRA Renegade Champion 2016 NMRA Coyote Modified Record Holder Worlds Fastest 5.0 Coyote and First in the 6's!! TO PROTECT OUR VALUABLE RESEARCH AND TESTING WE DO NOT SHARE OUR SPRING SPECS

For installation use MMR spring compressor PN#451564


2011-2017 Mustang GT, BOSS and F150 5.0 Engines 

  • Model: 400444


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