LONDON, OCT. 28 -- Jorge Vaca of Mexico became the World Boxing Council welterweight champion today, dethroning Britain's Lloyd Honeyghan in a confusing and controversial finish to an explosive fight.

Vaca was awarded the title by a split decision after the fighters banged heads in the eighth round of a scheduled 12 and Vaca was left helpless in mid-ring, blood spurting from his right eye.

After 15 minutes of confusion while officials consulted the rule book, Vaca's hand was raised in triumph.

Under WBC rules, Honeyghan was penalized a point for the head butt and the judges were asked by U.S. referee Henry Elespure to score the previous seven rounds only. The point deduction proved crucial as two judges, Chuck Hassett of the United States and Bob Logis of Belgium, favored Vaca, 67-65 and 67-66. Malcolm Bulmer of Australia had Honeyghan ahead, 67-65.

"We think it was a fair decision," Ignacio Huizar, Vaca's comanager, said as the new champion left the ring, his head wrapped in a white towel. "But . . . we will certainly give Honeyghan a rematch."

As Vaca's record improved to 43-5-1, Honeyghan suffered his first defeat in a 32-fight career.

"I definitely thought Lloyd was ahead," said Mickey Duff, Honeyghan's manager, although the seventh-round bell seemed to have saved his man as Vaca pummeled him on the ropes, and Vaca pressed the attack in the eighth. "I'm sure the WBC will order a rematch . . ."

The outcome also vacated Honeyghan's International Boxing Federation title. He said he may quit anyway.