Metro officials asked an arbitrator yesterday to allow them to delay paying a $7.6 million cost-of-living raise on July 1 to 5,000 transit workers.

The issue is so volatile, top Metro officials and union members agree, that it could lead to a wildcat transit strike this summer as it did for eight days in 1978.

The Metro plan to delay paying the cost-of-living increase was vigorously opposed by Local 689 of the Amalgamated Transit Union before arbitrator Richard I. Bloch. Bloch promised after a three-hour hearing to rule on May 29. Metro General Manager Richard S. Page has publicly promised to abide by Bloch's ruling.

Metro's bus drivers, train operators, station attendants and mechanics have been working without a contract since April 30. The contract provides, however, that all its provisions remain in force until a new contract is arbitrated.

One provision requires Metro to pay, four times a year, a raise equal in percentage to the increase in the Consumer Price Index for the Washington area. Metro does not want to pay that money on July 1 because it hopes that the new contract will contain a less generous cost-of living provision.

However, a separate arbitration on a new contract will not be completed until this fall. Then, under the old contract Metro would have to pay an enormous increase on July 1 to which union members might not ultimately be entitled. Then Metro would have to try to recover the extra money, a burdensome administrative task, Metro's Peter Sheehan said yesterday.

With the inflation close to 20 percent, the most recent cost-of-living increase in March cost Metro 26 cents per hour per bus driver instead of the 13 cents it had budgeted. The estimate for July 1, given the present contract, would total $7.6 million in the first four months of the new fiscal year. That figure would translate to a raise of about 25 cents an hour for each fully qualified bus driver.

Metro wants to place the full amount in an interest-bearing escrow account, then pay the appropriate amount to each employe once the contract is settled.

The problem is that the same arbitrator ruled on the same issue in 1978 that the contract means what it says when it says its provisions "shall remain undisturbed" and that Metro had to pay regardless of whether the whole contract was settled.

Charles Boswell, new president of Local 689, said yesterday during a break in the hearing that "some of my members don't even want me down here. They believe that when a man has ruled, he has ruled."

Sheehan, a labor relations specialist for Metro, said that "this is not the same case as 1978" because Metro this time was offering to escrow the full amount and pay whatever was due. The present practice, Sheehan said, is "a ripoff of money we . . . may not owe our employes. Union jobs will be lost if the money runs out." He called Metro's proposal "a unique remedy that protects both interests."

Thomas R. Roth, counsel for the union, said that "transferring dollars to a savings account is not in the best interest of the employes. We'll be the judge of what's best for them."

Sheehan said he believed the cost-of-living provisions would be reduced in the final contract, because three such adjustments have been arbitrated for other big-city transit systems recently and 12 such reductions have been negotiated.

Metro's budget for the year beginning July 1 assumes a 6 percent increase in salaries for Local 689's members. Metro's formal shopping list in its contract negotiations includes requests for a moratorium on transit worker salary increases for that same year plus a 6 percent ceiling in any subsequent 12-month period.

The union wants the cost-of-living increase to be paid six times a year instead of four, plus improvements in pensions and health and welfare benefits. i

The only real issue, however, is the cost-of-living payout. Metro board pressed local governments, have pointed out that no other public employe receives the same quality of protection against inflation as the transit worker.