After refacing a valve and recutting the valve seat, how can you compensate for the change in valve spring height?

To address the change in valve spring height caused by refacing a valve and recutting the valve seat, adding a shim under the valve spring is a practical solution. When the valve is refaced, it is ground down to ensure a proper seal with the seat, which effectively reduces the overall height of the valve assembly. This reduction can lead to undesirable changes in valve spring preload, potentially impacting engine performance.

By adding a shim under the valve spring, you restore the necessary height and preload to maintain proper spring tension. This adjustment ensures that the spring operates within its designed range, enabling efficient valve operation and helping to prevent issues such as valve float at high RPMs. This method is also less invasive and more cost-effective than other options, such as replacing the springs entirely.

Other options may not appropriately address the change in valve spring height. For instance, replacing the valve spring is more costly and may not be necessary unless the spring is worn or damaged. Shortening the valve guide could negatively affect the valve's stability and alignment, leading to further engine issues. Increasing valve lift alters the dynamics of the engine, which may not yield the desired outcomes and complicates engine tuning. Thus, the most efficient way to compensate for the change after valve work is to