6.1 cylinder head bolt tq specs

From the Factory Service Manual:

Tighten the cylinder head bolts in three steps using the sequence provided :
• Step 1— Snug tighten M12 cylinder head bolts, in sequence, to 34 N·m (25 ft. lbs.) and M8 bolts to 20 N·m (15 ft. lbs.) torque.
• Step 2— Tighten M12 cylinder head bolts, in sequence, to 54 N·m (40 ft. lbs.) and verify M8 bolts to 20 N·m (15 ft. lbs.) torque..
• Step 3— Turn M12 cylinder head bolts, in sequence, 90 degrees and tighten M8 bolts to 34 N·m (25 ft. lbs.) torque.

So it appears that the M12 are the Torque to yield fasteners. The factory recommends against reusing the Torque to Yield though some have done so with satisfactory results. As alway your mileage may vary.

Regards,

Joe Dokes