In-Block Balancing
This method takes into account the rotating part of the con-rod and
is especially true for asymmetrical crankshafts (group 2) whose asymmetrical design requires the use of compensation weights to be attached when balancing in the conventional way. Obviously when 'In-block balancing' is carried out these compensation weights are not required as rods and pistons are attached to the crankshaft. Prior to 'In-block balancing' the rods and pistons are still mass balanced with each other.
Here can be seen a 'Ford V8 351 Windsor' being run up on the balancing machine, engine speed during this procedure is about 700 rpm and only lasts for 10 seconds or so. The red blur on the pistons is Plasticine! this is used to replicate the weight of the piston rings which would create to much friction for the drive motor to overcome.