West Philadelphia and Dunbar of Baltimore advanced to a semifinal matchup today after victories last night in the Knighjts of Columbus 23rd Invitional scholastic basketball tournament at Catholic University.

West Philadelphia used a bullish inside game to stop Georgetown Prep, 89-65, and a pair of quick guards pushed Dunbar past Spingarn, 89-78.

Dunbar of Washington faced Cardinal Gibbons of Baltimore and Philadelphia's Roman Catholic squared off with St. John's in night games. The winners will meet at 8:45 tonight after Dunbar of Baltimore and West Philadelphia play at 7:15.

It was the 90th win in the last 100 tests for West Philadelphia, the defending tournament titlist and Philadelphia city champions. Despite their nickname, the Speedboys relied on the inside strength of 6-foot-7 Clarence Tillman and 6-8 Vincent Ross ot overpower Prep. Speedboys, now 31-1, led by only 10, 41-31, at the half as Prep's 6-7 Mike Mulquin battled the two Philadelphia giants to a near draw.

Tillman scored 10 third-quarter points to send the Speedboys into a 60-45 lead.

With Marquin and point guard Pat Luce each picking up their third and fourth fouls in the third quarter, Prep abandoned any attempts to beat Philadelphia inside and relied totally on the outside marksmanship of quick forward Brian Murphy who put in 18 of Prep's 34 second half points.

Dunbar of Baltimore raced to a 17-point lead, 61-44, with 4:21 remaining in the third quarter and held off Spingarn. The victory was the 20th in 21 outings for Baltimore's public school champions.Spingarn slipped to 22-5.

Poet guards Dwayne Wallace and Calvin Maddox continually beat Spingarn defenders on drives and broke downcourt for release passes to convert Spingarn misses into Poet points.

The two also lead a continuous parade of Poets to the free-throw line. Wallace scored 13 of his 25 points at the line, while Maddox had four freebies among his 20-point count.

Spigarn's chances of countering Dunbar's superior guard play were hampered by the foul problems of 6-7 pivotman Bryant Johnson, who contributed 19 points and helped clog the middle in his limited paying time.

Spingarn's top season, Diego McCoy, was shut out until 1:30 to play in the third quarter when he scored on a follow shot for his only points of the game.

The contest closed on a subdued note when Maddox lost a front tooth after being spilled while making a layup with 1:32 to play.