Class '83 took full command of the match from start to finish to chalk up its first victory. Stephen Tan showed the way for the Chester Enterprises-backed squad with 15 points followed by Resil Yu with 11 markers.
Class '83 enjoyed a not-so comfortable 37-30 lead after three quarters, but had a solid fourth quarter show to rebuff Young Builders' repeated attempts to change the course of the game.
Juan Borromeo, Jr. was the only double digit scorer for Class '91 with 10 points.
In the other game, Cebu Pacific Transport Corp. '99 weathered a spirited endgame resistance by JRJ Enterprises 2000 to breeze through a 62-59 win.
Class '99 started hot and went on to close the first half with a 10-point advantage, 36-26.
The two teams fought on even terms in the third canto, but Class 2000 rallied back in the closing minutes of the game.
However, Class '99 proved to be a tough nut to crack at crunchtime to preserve the three-point victory.
Ruben Yap, Jr. topscored for Class '99 with 17 points, whileAlbert Uy chipped in 12 markers.
John Brian Lo scattered a season-high 27 points, but his solitary effort couldn't work wonders as Class 2000 crashed to its second straight loss in as many starts.
The scores
First game
Class '83 (54) - Tan 15, Yu 11, Ting 8, Lim 8, Co 4, Cokaliong 4, Yu 2, Ku 2
Class '91 (45) - Borromeo 10, Go 8, De la Torre 8, Crisologo 6, Lim 4, Go 4, Co 3, Mission 2 Second game
Class '99 (62) - Yap 17, Uy 12, Lauron 7, Tan 6, Ang 6, lao 6, Sia 4, See 4
Class 2000 (59) - Lo 27, Peña 14, Azarraga 7, Pimentel 6, Ocarol 3, Kua 2