found it.
Do not reuse the cylinder head bolts. New cylinder head bolts must be used. The cylinder head bolts are torque-to-yield bolts and cannot be reused once the initial torque is applied. During the initial torque of the cylinder head bolt, the cylinder head bolt is stretched to achieve proper clamp load, which will not be achieved if a used cylinder head bolt is torqued again. A stretched cylinder head bolt can also break when torqued. Failure to replace the used cylinder head bolts with NEW cylinder head bolts can lead to improper clamp loads and extensive engine damage.