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This thoroughly proven spring set has powered 4g63 vehicles ranging from 6-second drag cars to high-mileage everyday drivers. Introduced in 2006, these were the first beehive valve springs available to the 4g63 platform. They are the best spring set you can use when targeting boost levels up to about 45psi and 11,000rpm.
Featuring PAC ovate wire "beehive" springs, designed with s a stress-optimized profile that minimizes spring mass and maximizes natural frequency. This means better stability at high rpm usage. The beehive design also features a variable natural frequency, resulting in better stability during surge points and self-damping. Combining these advanced design features with aerospace quality production and shotpeening results in a high performing, reliable combination.
The spring set includes our proprietary titanium retainers and steel seats to achieve an appropriate seat pressure that will prevent excessive wear in long-term street applications. The precision CNC machined grade 5 titanium retainers are optimized for mass and stress levels using finite element analysis and packaged for maximum clearance to the valve stem seals. Any OEM replacement or smaller diameter valve seals can be used and clearance to the retainer is about 14mm.
In higher boost drag racing applications these springs can be shimmed for increased seat pressure. The limiting factor in the 4G63 valvetrain is typically boost levels, not RPM. To protect against this, we recommend targeting seat pressure at about 1.7x your absolute manifold pressure (boost + 14.7psi). This tends to be the worst case scenario and varies widely with the engine’s parts combo.
