World Seniors Snooker Championship: Jimmy White lights up the Crucible
Joining Lilley are two former champions in White and Peter Lines while Lee Walker will be chasing a maiden title on Sunday.
Tournament favourite Michael Holt proved no match for Lilley, going down 4-0 on Saturday.
A century in the second frame gave White a new tournament high break and he would go on to secure his 13th win in 14 Seniors Championship matches.
UK Seniors Champion Lines joined the final four thanks to his 4-1 victory over another former champion Nigel Bond.
He fought back from 2-0 down to gain his spot in the final quartet.
The semi-finals will be contested as best of seven frame matches, while the final, scheduled to start at 19:00 GMT, will be a nine frame match.