In 1969 the 4 bore block was updated to incorporate four bolt main bearing caps and increased thickness main bearing webs Since this is the block of primary interest the 283 and 307 displacement engines will not be considered in the text THE 400 CU IN SMALL BLOCK In 1970 a 4 l B bore block was introduced in regular pro duction as a 2 barrel carbureted regular fuel engine at 400 cu in displacement This block features siamesed cylinder bores no cooling water between bores four 4 bolt main bearing caps and an increase in main bearing diameter to 2 65 It also uses a nodular iron crankshaft and 5 565 length connecting rod vs 5 7 for all other small block engines 4 3 Because of the potential for larger displacements and new j bore stroke ratios from the 400 cu in block a great deal 2 of interest has been shown by engine builders in using it 1 A Some parts common to other engines such as camshafts cylin g der heads and intake manifolds are interchangeable Due to f the lack of suitable crankshafts connecting rods and pistons no instructions are included on this engine except as follows i In the event you should attempt to build a high performance engine using the new 4 l 8 bore block the following cautions l should be observed l This engine at 3 75 stroke in production is externally balanced with an unbalanced torsional damper and flywheel These parts or similarly I unbalanced parts may be necessary to achieve final E engine balance V l f i 2 Because of the siamesed cylinder bores steam holes L K are drilled through the cylinder block between I V c E Ugg i L 1 li 4 11 16 70 1 i Y F J