I am rebuilding my QG18 1.8l engine on my 2003 Sentra. I have the front cover off and the cylinder head off. When I put the timing chain back on, how to I prevent the chain from slipping off its proper position on the crankshaft sprocket once the front cover is back on before I replace the cylinder head and camshafts? This seems like a stupid question but I can't figure out what keeps the timing chain from slipping before I reinstall the camshafts. I would appreciate one of you great guys helping out. Thanks.