the drill marks are to balance the balancer itself, not the engine, but I think having the wrong type balancer for that engine can cause problems, as they are the 'external balancing' - the 'harmonic balancer' is to take care of the particular harmonics developed by that design of engine, so they're different for different engines, tho 216 and 235 may be close enuff - that said [I think!], I'd check out the flywheel/clutch assembly, which can also be unbalanced like truckedup sez
Bill
