I have a Briggs and Stratton 19.5 hp Intek engine with OHV, which the bottom pushrod was worn down. I purchased a replacement part, and installed it, adjusted the valves and when I turn the engine by hand, the push rod is compressing the valve spring completely, and slightly bending the rod in the process. Any ideas what will cause this? The steel rod is functioning normally, just the aluminum rod is pushing out too far.