Understanding guide plates and their proper installation is crucial for engine performance and longevity. This guide will walk you through the process, explaining when and how to use guide plates effectively, ensuring optimal pushrod alignment and preventing potential engine damage.
Guide plates are essential components used to maintain proper alignment between the pushrod, rocker arm, and valve stem. They are particularly important when using aftermarket cylinder heads or when upgrading to high-performance valvetrain components. Without guide plates, the pushrod can wander, leading to premature wear and potential engine failure.
Here’s a look at a guide plate installed on a Trick Flow Twisted Wedge head. Notice the round pushrod hole, which is much wider than the pushrod itself. This design necessitates a guide plate for proper alignment.
Understanding Pushrod Slots and Guide Plate Necessity
Factory GM heads typically feature a pushrod slot with a slight oval shape. This design provides some inherent support to the pushrod, helping to maintain alignment. However, when using aftermarket heads or high-performance components, this support may be insufficient, making guide plates necessary.
Caution: Guide Plates on Factory Heads
Never install guide plates on factory GM heads unless you widen the pushrod slot. The guide plate and the factory slot will likely be misaligned by a few thousandths of an inch. This misalignment will cause the pushrod to bind, bend, or even break. Widening the slot ensures proper clearance and prevents these issues.
Self-Aligning Rocker Arms: An Alternative to Guide Plates
Self-aligning rocker arms are designed for use with heads that lack the oval-shaped pushrod slots or guide plates, such as Vortec heads. These rocker arms feature a design that allows them to align themselves with the valve stem tip.
The stamped steel factory rocker arms, commonly found on Vortec engines, extend over the sides of the valve stem tip, providing the necessary alignment.
Aftermarket roller rocker arms designed for self-aligning applications typically have small “washers” on each side of the roller tip. These washers keep the rocker arm aligned with the valve stem tip.
Regular rocker arms lack these “washers” and rely on guide plates or the pushrod slot for alignment.
Important Considerations When Choosing Rocker Arms
Avoid using self-aligning rocker arms on older style heads. The “washers” designed to align the rocker arm with the valve stem tip can interfere with the valvespring retainer and lock. This interference can lead to serious and costly engine damage. This is analogous to using guide plates on factory heads without first widening the pushrod slots – creating a problem where none existed.
Conclusion
Proper pushrod alignment is vital for engine performance and reliability. When installing aftermarket cylinder heads or upgrading valvetrain components, carefully consider whether guide plates are necessary. If using guide plates on factory heads, ensure the pushrod slots are widened to prevent binding. Alternatively, self-aligning rocker arms offer a solution for heads without pushrod slots or guide plates. By understanding these principles, you can ensure your valvetrain operates smoothly and reliably.
