Abstract: A cast iron gas turbine engine block has an integrally formed internal wall configuration which defines a centrally located exhaust gas passage through the block and a radially outwardly located cooling air passage for directing cooling gas around the exhaust gas passage, a pair of separate inner walls are spaced apart and each includes a plurality of integrally formed circumferentially arranged posts thereon directed into the passage and having the tip portions thereon formed in situ of side grooves on a steel turbine wheel containment ring: the ring of posts in each of the side wall grooves of the ring locate it radially outwardly of an annular inner wall of the cast iron housing and form air flow openings around the ring to enable the cooling air directed through the cooling air passage to completely surround and circulate around the ring for cooling it during turbine operation.