The half-inning finally ended when Clarissa Maldonado flied out.
The Eagles came out with flight but not enough to overcome the 5-0 deficit that would face Southwest for the next two and a half innings.
Perez opened against Lauren Miramontes, who flied out, but Mary Sanders then singled.
P.J. Enders was the second out for the Eagles when her bunt on a third stike went foul.
Melissa Frausto advanced Sanders to second with a single, but Perez struck out Jessica Conway to end the inning.
In the second, Claudia Maldonado flew out to Sanders, who made a spectacular catch to save a single, but the next two Spartan batters got on base on an error and a walk, respectively.
Grundman's fielder's choice was the second out and Long flied out for the third.
The Eagles did nothing offensively in the inning.
In the fourth, Clarissa Maldonado got on with a walk and Claudia Maldonado was hit by a pitch.
Ramirez then singled and Perez walked with the bases loaded to score Clarissa Maldonado for a 6-0 lead.
Grundman singled to score Claudia Maldonado and Ramirez scored on a wild pitch for an 8-0 lead.
The three remaining innings passed with no scoring and Southwest's Jackie Martinez stuck out in the bottom of the seventh for the final out.
"It's a good win," Central coach Sandy Montalvo said.
"It's always good to finish on a winning note," she added.
She said the Spartans are looking for a good playoff seed in the CIF-San Diego Section and the win helps a lot.
"It always looks better to have as many wins as you can get," Montalvo said.
She added her team was excited and that led to the explosive first inning. She commended Grundman, who played shortstop.
"I'm excited to see some new clubs," Montalvo said of the playoffs. "I'm anxious to see what they have."
Montalvo said she is confident the Spartans will make a good game of it no matter who they play and she noted 17 of Central's wins were shutouts.
San Diego Section coaches will meet Thursday to determine playoff slots.
Brawley 9, Calexico 1
BRAWLEY — The Brawley Union High School softball team knocked off Calexico High 9-1 to finish both teams' regular seasons here Wednesday.
Audrey Corpuz picked up the win for the Wildcats (17-6, 9-3). She struck out 12.
Ebony Lofton led the Brawley offensive attack with three hits.
Calipatria takes twin bill
BORREGO SPRINGS — The Calipatria High School softball team downed Borrego Springs twice in a doubleheader here Wednesday.
The Hornets earned wins of 17-4 and 12-2 to improve to 9-11, 5-3 Desert Mountain League.