Harvard's lightweight crew-recognized as the finest in the school's history-will break all precedents in collegiate rowing Monday and Tuesday when it competes against the nation's best heavyweight crews in trials for the Pan American Games at Lake Onondaga, N.Y.

The lights suffered a minor setback yesterday when their Stempfly shell-the infamous "Superboat" unofficially and the Thorne Thompson shell officially-was destroyed in an accident on the Mass Pike en route to Lake Onondage.

The truck carrying the shell had stopped at a toll booth when another truck slammed into its rear. While the shell was rendered useless, the riggings for the boat are intact and will be moved to another Stempfly being borrowed from Princeton.

The Princeton boat is expected to arrive in time for the lights to practice in New York as originally planned.

The lights' coach, Steve Gladstone, had originally sought a spot in the Intercollegiate Rowing Association Championships this Friday and Saturday. But the IRA refused to allow a lightweight crew to challenge its heavy-weight contenders, so Gladstone and the lights chose the Pan Am trials instead.

Perhaps the refusal by the IRA will turn out to be a good turn for the lights, since the trials-which include the best boats from the IRA Championships and other club boats-carry even more prestige.

As ludicrous as the lightweights' challenge seems, there is a good chance they will make good their bid to represent the United States against international competition in the Pan Am Games from July 31 to August 2.

Heavyweight crews are generally having an off year-"a good year but not a great year," according to one heavyweight coach.

Gladstone realizes the boldness of the lights' challenge, but he is optimistic despite yesterday's accident. "There's no way a great lightweight boat would beat a great heavyweight boat," he says. "But a great light against a good heavyweight-that's something different. I think we've got a chance."

The lights-who did not lose this spring and won the Eastern Sprints by over four boat lengths-are also scheduled to row in the Henley Regatta in England from June 30 through July 3 and another international regatta in Lucerne, Switzerland. in early July.

The primary goal. however, is to win next week and earn the right to continue on to the Pan American Games in Calais, Colombia.

The funds for this meager international spree are being provided by Friends of Harvard Rowing, who agreed to subsidize the lights after the crew voted to continue its season into the summer.

The Friends' willingness to contribute is not surprising, though, in view of the caliber of this year's lights. When the season started, all eight oarsmen from the undefeated 1970 boat were back; but by the first race, two returnees had been bumped by sophomores up from the 1970 unbeaten freshman crew.

Indeed, this attests to the quality of Gladstone's entire lightweight program. In three years as coach of the varsity, JV and freshman lights, he has yet to lose a race.

And this group is the best of the lot. The long list of superlatives used to describe the lights has nearly been exhausted, but the fact remains that Gladstone has assembled one of the finest 150-pound crews ever.