Ford valve springs are designed to work with a certain lift cam, and since most aftermarket cams have higher lift, the spring must be addressed.
It is highly recommended and a requirement of most warranties that the suggested springs be installed along with a cam manufacturer’s recommended camshaft.
Most Ford cylinder heads utilized a step cast into the head that acted as the valve spring locator. When installing a dual spring, it is highly recommended that this step be removed by machining to minimize the possibility of coil binding the inner spring.
Whenever installing a high-lift racing cam in any engine, the cylinder heads must be equipped with the correct valve springs, screw-in studs, guide plates and hardened pushrods. The increased loads and ultra high speeds of the racing engines make this a necessity for valve train stability.
–Tech Tip courtesy of Comp Cams