Resurfacing the cylinder head of an OHC (Overhead Cam) engine can affect valve timing by altering the distance between the camshaft and the valves. If the head is resurfaced too much, the valve timing can be advanced, meaning that the valves will open and close earlier than they should, leading to poor engine performance.
When the head needs resurfacing, it is important to consult the manufacturer's specifications to determine the maximum amount that can be removed from the head without affecting the valve timing. In some cases, it may be necessary to replace the camshaft and adjust the valve clearances after resurfacing the head to ensure that the valve timing is correct.
Additionally, it is important to inspect the valve seats and replace them if they are worn or damaged. This is because resurfacing the head can affect the valve seats and lead to valve leakage, which can cause engine performance issues. By inspecting and replacing the valve seats as needed, the engine can maintain proper compression and operate at peak performance.