Most late-model engines make use of some sort of variable valve timing system; overhead-cam Ford three-valve modular and 5.0-liter Coyote and the General’s Gen IV LS engines use some sort of internal cam phaser mechanism to make this possible. The variable valve timing system in the GM engines can adjust the timing up to 52 degrees; the modular/Coyote engines have nearly as much range of motion. Adding more lift or duration than the stock camshaft dimensions are where problems will occur.

When building a performance engine with a hot camshaft, it’s not optimal to allow the camshaft its full range of motion, as this can cause interference between the valves and the pistons — an unwanted (and expensive) collision by every definition.

The fix is in. Comp Cams has the solution in the form of its phaser locks and limiters for these domestic engine types that use variable valve timing. What do they do? Exactly what their name implies — lock or limit phaser operation to prevent the dreaded valvetrain crash while gaining the ability to install the hot camshaft profile — without losing the emission-friendly capabilities of the variable valve timing in non-race applications where limiters are used. Ford applications become limited to a 20-degree range of adjustment, while GM applications retain 22 degrees of swing.

For example, in the Coyote engine, the locks are used by the builder to set the timing exactly where it’s best for performance, which allows precise control at high RPM levels. They are adjustable over the entire phaser range of motion of 50 degrees and then are locked down to maximize performance.

Most aftermarket EFI systems compatible with the Coyote engine require the camshafts to be locked in place. Using the phaser limiters in place of the locks with the Coyote permits the tuner to control the intake and exhaust centerlines through the software.

The helpful video below with Comp’s Billy Godbold adds more details to the theory behind the technology. Check it out!