You text says cylinder head  , not cylinder. Cylinder would be easier as it has a cast iron liner ( usually )in the aluminum casting. I can promise you the head is not 6061 or any other wrought alloy. You are looking for 3 digit casting numbers. I found 356 and 319 are ( or were) very common alloys in automotive castings  . Strength will be lower, Like all aluminum they are age hardenable to some degree; both would heat-treat to about 24,000 psi yield strength. Stresses would be seriously difficult to calculate  , I think finite element techniques would be needed. Even those few approximately hemispherical combustion chambers would need to allow for 6 openings for valves (4)  , spark plug  , and fuel injection.

You text says cylinder head, not cylinder. A cylinder would be easier as it has a cast iron liner (usually) in the aluminum casting. I can promise you the head is not 6061 or any other wrought alloy. You are looking for 3 digit casting numbers. I found 356 and 319 are ( or were) very common alloys in automotive castings. Strength will be lower, Like all aluminum, they are age hardenable to some degree; both would heat-treat to about 24,000 psi yield strength. Stresses would be seriously difficult to calculate, I think finite element techniques would be needed. Even those few approximately hemispherical combustion chambers would need to allow for 6 openings for valves (4), spark plug, and fuel injection.