Flow General Inc. of McLean yesterday announced record sales and earnings for its fourth quarter and fiscal year ended June 30.

Fourth-quarter net income increased by 97 percent to $1.267 million (30 cents per share), compared with $643,000 (20 cents) for the year-earlier period. Sales in the fourth quarter rose 27 percent to $21.616 million from $17.08 million in 1979.

Earnings for the year were $77.065 million ($1), compared with $60.21 million (69 cents) for the previous year. Per-share earnings for the year and the quarter reflect a 2-for-1 common stock split on June 30.

Flow General does high-technology research and is involved in research with interferon for fighting cancer. It manufactures and sells biomedical equipment and biological products, specialized equipment for the radio and television broadcast industry and materials testing equipment.

First Financial of Virginia Corp., meanwhile, reported that its earnings for the fiscal year ended June 30 declined to $868,000 ($1.83 per share) from $2.24 million ($4.73) the previous year. First Financial President Richard Lawton blamed the decline from the record year-earlier earnings level on an unprecedented high cost of money because of federal government policies and on a decrease in loan volumn.

Virginia Power and Electric Co. announced that its earnings in July increased, raising 12-month earnings by 4 cents per share from the June figure. For the 12 months ended July 31, net income was $206.19 million ($1.64 per share) compared with $197.77 million ($1.71) for the same period the previous year. The average number of shares of common stock outstanding increased from 83.7 million in the 1979 period 91.5 million for the 1980 period.

Vepco President William W. Berry attributed the earnings rise in July to the hot weather, which increased electricity use.

Wapora Inc. of Chevy Chase, an environmental and energy contract research firm, reported record earnings and revenues for the fiscal year ended June 30. Net income rose to $231,554 (39 cents per share) from $224,082 (37 cents) from the previous fiscal year. Revenues increased from $6.48 million in the 1979 fiscal year to $6.67 million for the 1980 fiscal year.

Riviere Realty Trust reported first-half earnings of $350,860 (45 cents per share), because buildings sales and an extraordinary credit for utilization of the prior year's operating loss carryforward more than wiped out a deficit of $622,415. The trust reported a second-quarter loss of $246,638, increased from the loss of $134,960 for the second quarter of 1979.

Doughties's Food Inc. of Portsmouth reported its second-quarter net income declined to $88,000 (12 cents per share) this year for the period ended June 28, compared with $141,000 (19 cents) for the same period last year. First-half earnings increased, however, to $230,000 (30 cents) for 1980 compared with $204,000 (27 cents) for the 1979 period. Per-share earnings reflect a 10 percent stock dividend paid to stockholders of record on June 2.