As Laurel Race Course opened its 48-day summer meeting yesterday, General Manager Ken Schertle admitted, "I just don't know what to expect. Do you?" This sentiment probably was shared by most of his 7,885 customers.

Ordinarily a horseplayer who goes to one of the Maryland thorougbred tracks will be greeted by no surprises. At Pimlico he can be prepared to bet speed horses with inside post positions. At Bowie he can be prepared to be depressed by the environment.

But this was Laurel's first summer season since 1963, and yesterday the track introduced a new 2 p.m. post time, a new air-conditioning system, a new finish line, a new admission policy and a new array of arcade games, including Pac-Man, in the grandstand.

To be sure, Laurel did not evoke many comparisons with Saratoga or Royal Ascot yesterday. Because there is so much competition for the betting dollar in the East at this time of year, Laurel's management does not expect massive business, and prepared for this eventuality by not spending massive amounts of money.

Only half the plant was air-conditioned, and patrons pay a flat $3 admission to the cool end. The other half of the grandstand is roped off and those thousands of empty seats create something of an eerie atmosphere.

Nor did Laurel spend vast sums on physical beautification of the grounds. The infield looks as if it had been a victim of the scorched-earth policy that prevailed during the Vietnam war. The turf course is blighted by a number of barren patches that are going to drive some horses to distraction.

In another move that suggests the track's preoccupation with keeping costs down, the fields for races will be limited to 10 horses, thus saving the salaries of a couple of jockey-room valets and members of the starting-gate crew.

But Laurel's customers were not uttering many complaints; in fact they showed their enthusiasm for the summer meeting by pushing $1,008,619 through the mutuel windows yesterday, a Laurel summer meeting opening-day record. They know the track's shortcomings surely are preferable to the lack of action that existed at this time of the year before year-round racing came to Maryland. And while it may be easy to find fault with Laurel, the other tracks in the East--Delaware, Keystone, Monmouth and Atlantic City--are not going to be able to offer anything much better this summer. The population of horses and horseplayers is spread too thin.

One consolation for the esthetic deficiencies of the summer meeting is that Laurel should offer some interesting betting opportunities in the next week or two.

Most of the horses here have been racing at Pimlico, where, since April 29, the vast majority of races were won by speed horses on the rail. Stretch runners had virtually no chance.

Now the game is going to be different. The Laurel track appeared to be uniform yesterday, with no particular bias in favor of the inside or the outside. It also gives stretch runners a fair chance, which they did not have at Pimlico. Because Laurel has moved all its spectators into the clubhouse end of the track, it has brought the finish line in front of the clubhouse, a sixteenth of a mile past its usual location. This gives Laurel the second-longest stretch run in North America. Only the stretch run at Fairgrounds Race Course in New Orleans is longer.

Horses who led from wire to wire at Pimlico won't be so formidable here. Horses who tried unsuccessfuly to rally on the outside at Pimlico will have much more success at Laurel. Alert bettors will have a chance to profit from some sharp reversals of form.

Where else can you cash a bet on a logical long shot and play Pac-Man, too?