The 427 RPO L 88 features open combustion chamber aluminum i heads introduced first in 1969 The 1968 and earlier aluminum heads and all cast iron heads will not fit on these engines V due to piston to head interference I Additionally available for 1970 was the RPO LS 6 454 cu in engine which features ll l compression ratio forged pistons with pressed pins mechanical valve lifters and high perfor mance conventional combustion chamber cast iron heads with a low profile aluminum intake manifold Any 427 cu in engine with four bolt main bearing caps can V be upgraded to RPO L 88 427 or 454 cu in heavy duty speci Q fications by using components from the Dealer Catalog having the Heavy Duty Parts Section E NOTE Caution should be exercised in increasing displacement jp to 454 cu in Additional connecting rod clearance may be j r required in the block and the proper torsional damper and fly wheel should be used to obtain correct engine balance Due to V g Q the increased stroke it is not possible to internally balance theengines with the crankshaft counterweights so part of the i balance is included in the damper and flywheel Q LS 7 454 Heavy Duty Engines were not produced on the assembly Q line Those in existance were built up from service parts fi B Q vc r i n 4 tp 1 uy i V jr 1 j J v G H i 7 V llel 70 g 1 A i 1 Wi