Rope length for replacing valve springs.

piston at bdc, feed in as much rope as will fit and turn the crank' until the rope jams the piston. the valves are now held. also as above tap the edge of each retainer to break the seal between it and the locks. with the air method there is that possibility of dropping a valve onto the piston, with rope it just can't happen as they're physically held. oh, and a length of rope is cheaper than even a cheap compressor.