What size is a bolt for harmonic balancer for a small block Chevy? ARP2342504 - Chevy Gen III/LS7 Small Block Harmonic Balancer Bolt Kit,M16 X 2.0 Dia, 5.225 Uhl, 1-1/16 Socket Size. Are SBC and BBC flywheels the same? Registered.no they are not.. iirc the big block flywheel has ...