Technician A says you should use bolts and rubber bands above a cylinder to catch a piston. Technician B says you should place protective covers on the rod bolts to protect the rod journal. Who is correct?

 Technician B is correct in suggesting that you should place protective covers on the rod bolts to protect the rod journal. When you are disassembling an engine and removing the pistons, the rod bolts that fasten the connecting rod to the crankshaft can damage the rod journal surfaces if they are not covered. This is because as the piston and connecting rod are maneuvered out of the engine, the exposed threads of the rod bolts can scratch or gouge the journal, leading to costly damage. Using protective covers such as plastic sleeves or rubber hose pieces over the rod bolts can help to prevent this type of damage.

Technician A's suggestion to use bolts and rubber bands above a cylinder to catch a piston is not a standard or safe practice for piston removal from an engine block. In fact, it is unclear how exactly bolts and rubber bands would function in this context. Removing pistons typically requires careful movement and support, ensuring not to damage piston skirts, cylinder walls, or other engine components. Service manuals provide the specific procedures for safely removing pistons from an engine.