The last time anyone checked, Chip Hooper hit a tennis ball 127 miles per hour. That was with an ordinary, teeny-tiny racket four years ago. Now this fellow with the power-forward/tight-end body has taken up with one of those snowshoe rackets, and on Wimbledon's second dark and rainy day, he caused lightning bolts to leap from the racket strings.

A mostly anonymous Californian who bounced from one college to another until turning pro with a thin resume last summer, Hooper breathed life into Wimbledon today by upsetting eighth-seeded Peter McNamara, 7-6 (7-4), 3-6, 6-2, 6-4.

"For the first time ever, I didn't feel like I was playing tennis," the euphoric Hooper said minutes after an unforgettable debut at the All England championships. "Wimbledon is such a big thing . . . It's like a big picture show. This is like I'm playing in some different planet. There's a totally different aura."

If it might take Hooper "three or four beers before it sets in" as to what he did here today, three-time champion Chris Evert Lloyd began women's play in workmanlike routine with a 6-0, 6-4 stroll past trembling teen-ager Barbara Gerken. The women's excitement came from Virginia Wade, the 1977 champion, who cheered her countrymen with an unexpected three-set conquest of up-and-coming Jo Durie.

The only other seeded player in action today, Gene Mayer, No. 6 among the men, defeated Tim Gullikson, 5-7, 6-4, 6-1, 7-5.

"I was nervous--because I thought I could win," Hooper said of his first trip to the planet Wimbledon, where alien creatures wear mauve and green club ties and worship the grass of an awesome spot called Centre Court. Whatever nerves bothered him surely were not in his right arm, for Hooper's cannonading serve so demoralized McNamara that the Australian, ranked 13th in the world in the latest computer listing, could do little more than protect himself against the fuzzy missiles flying his way.

"During the tie breaker in the first set, I was serving so confidently that I was just going for broke," said Hooper, who began this year No. 235 on the computer and has worked his way to 23rd.

Hooper won six of the last seven points in the tie breaker to win the first set he ever played at Wimbledon. Four of those times McNamara, who reached the quarterfinals here last year before losing to Bjorn Borg, could do nothing with Hooper's serve except feebly deflect it with the outer edge of his racket.

Before leaving Court 1 with McNamara's psyche in his racket cover, Hooper demonstrated that his considerable size is not the forbidding obstacle one expects on a tennis court. At 6 feet 5 1/2 and 210 pounds, he could pass for the young Muhammad Ali, so perfectly is he done. With the size comes enough agility to handle all the work--the instant volleys, the half-volleys on the sprint, the crosscourt dashes for a forehand--necessary to work tennis wonders on any planet, even earth.

McNamara avoided questions from the press afterward, but his head-down shuffle off the court was eloquent enough. It came after the Aussie put up a lob that he believed a neat piece of racket control, certainly a winner against an inexperienced giant. Nope. Up went the power forward's body. He didn't backpedal to get to a spot from which to hit the lob after its bounce. Nope. Up went the tight end for a high pass, and then, crashing down, came the tennis player's overhead. He bounced the ball 20 feet high. Game, set, match, welcome to the big time.

Twice college all-America and the top seed in the 1981 NCAA tournament (from which he defaulted with cramps), Hooper actually had served notice on the pros earlier this season by reaching the semifinals of two tournaments and racking up a roster of victims that includes Roscoe Tanner, Peter Fleming, Brian Gottfried and Tomas Smid. He moved as high as 17 on the computer.

Hooper had trouble today only in the second set when the shadows of Court 1 most bothered him. "I played like a nerd," he said. "My motion got disjointed, and I couldn't see with the tall buildings and the sun and everything going from dark to light to dark."

This was after the day's second one-hour rain delay, which put off some matches until Wednesday.

In the third set, Hooper found his rhythm again, especially with the serve.

"I was like a pitcher," he said, going back into his history as an athlete for all seasons. "I was nipping at the corners, jamming him. He couldn't do anything with it when I was jamming him. By then, my big serve was going 17 feet out. I was a little nervous . . . 'Wow, Wimbledon, I'm up, 4-1, I'm winning' . . . It was a fretful situation."

Not to worry on grass when you have the big serve working, though, and few are bigger than Hooper's.

"Four years ago, they clocked it at 127," he said, quickly adding, "but that's farcical. I could hit it much harder now. I'm stronger, and I'm playing with the bigger racket."

In his first tournament this year, Hooper reached the semifinals at Philadelphia. "I just, wow, shot 'em down with a hundred aces in four matches," he said. "It's hard to lose when you do that."

Arthur Ashe, the Davis Cup captain and only black man to win Wimbledon, invited Hooper to cup practices last winter after Hooper underwent eye surgery to remove overgrowth of tissue on the cornea. Three days before Hooper's Wimbledon debut, Ashe predicted the upset that would come. "Thanks, Arthur, wherever you are," Hooper said. "That's a hell of a compliment."

Ashe spent most of today moving back and forth between Hooper's match and one involving another black youngster, Lloyd Bourne. "It's a nice gesture on Arthur's part to look after some of his black counterparts," said Hooper, who first met Ashe a dozen years ago at a time when he had Ashe's picture up on his bedroom wall.

Hooper, 23, was born in Washington while his father, Lawrence, was a medical student at Howard University. After high school in Sunnyvale, Calif., Hooper's spasmodic college career took him to Memphis State, Arkansas and Canada College in Redwood City, Calif.

He turned pro for last year's U.S. Open, where he lost in the second round. The next stop was Davis Cup practice, then came his dizzying rise on the computer, capped now by an upset of a world-class player at Wimbledon.

"I've done so may things this year," said Hooper, who has another 11 days here in which to conquer a new planet.