This block was cast-iron for the L-88 all three years, 1967 through 1969.
     The 1967-68 L-88 came standard with aluminum closed-chambered heads, featuring 2.19-inch intake/1.84 exhaust valves, screw-in studs, and pushrod guide plates. The casting number in 1967 was #3904392, but in 1968 it changed to #3919842. In 1969, the cylinder heads were completely redesigned to improve exhaust emissions, but the new open chamber design also had better flame travel and larger 1.88-inch exhaust valves to produce more horsepower than the previous head. The exhaust ports were also changed from the conventional rectangular shape to round. The changes in the cylinder head dictated a change in the piston dome as well. Although the piston was larger than earlier designs, the new piston only registered a 12:1 compression ratio, as compared to the earlier 12.5:1.
     Originally, the 1967-68 L-88 engines were equipped with the "double dimple" connecting rod that was used in all high-

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