The rocker tower bolts that hold the rocker shaft assembly on a Deutz 1011 or 2011 are a single-use bolt according to the manufacturer. When a timing belt breaks, the piston impacts the valve which drives excess force up through the push rods and into the rocker arm assembly, stressing the bolt threads holding the assembly in place. If the bolts are stretched and re-used they can loosen prematurely and cause further engine performance issues or damage. As a result they should not be re-used.
