The Montgomery County Democratic Central Committee, which strongly supported Sen. Edward M. Kennedy in the Maryland presidential primary, has voted to endorse an open Democratic convention.

The 12-to-5 vote with two abstentions Tuesday night is not binding on the six Kennedy and four Carter delegates who were elected in Montgomery to attend the New York nominating convention this month.

In the event of an open convention, in which delegates would be released from their commitments on the first ballot, neither Kennedy nor Carter forces expect many, if any, defections in the Maryland delegation. Thirty-two Maryland delegates are pledged to Carter, 26 to Kennedy, and one is uncommitted.

In Virginia, Richard Davis, the head of the state's Democratic Party, said yesterday he won't oppose a push by the delegation for an open convention if such a move is favored by a majority of the delegates. But Davis said delegates bound to President Carter or Sen. Kennedy should back their candidate on the first ballot, even at an open convention.

Fifty-nine of Virginia's delegates are pledged to Carter and five to Kennedy. None of the Carter delegates has demonstrated the slightest interost in switching to another candidate.

In Maryland, Ann Lewis, chief political aide to Rep. Barbara Mikulski (D-Md.) who is an official in Kennedy's convention organization and a proponent of an open convention, said: "People aren't hanging up on us, but we are not getting a lot of people to turn around, either.

"We've gotten the impression, don't push (the Carter delegates) or they will hang up on us," Lewis said.

Montgomery County Executive Charles W. Gilchrist, a Carter delegate, said, "I wouldn't intend to change my vote. But things are changing from minute to minute, and I don't know what the effect will be if they open the convention."

Bill Bradford, a Carter supporter who voted against the Montgomery Democratic committee's resolution, said, "I don't believe in changing the rules after the game is played.The delegates were selected not for who they are but for who they support."

The resolution, according to committee chairman Stanton Gildenhorn, reflects Montgomery County's constituency. A poll taken for Rep. Michael D. Barnes (D-Md.) shows President Carter running third in Montgomery county.

State law requires delegates to vote on the first ballot for the candidates they were elected to support, unless the party allows them to do otherwise.