LS6 bore: 3.898 in, stroke: 3.622 in The LS6 used hollow-stem valves to keep them cooler and reduce the chance of pre-detonation due to a hot valve. 427 cid/7.0 L bore 4.125 in/104.8mm and stroke 4.00 in/101.6mm The LS7 used titanium intake and hollow-stem sodium filled exhaust va...