Capital Cities-ABC Inc. yesterday reported second-quarter earnings of $67 million ($4.15 a share), compared with $41 million ($3.15) in the year-ago quarter.

Elsewhere, Eastman Kodak Co., Unocal Corp. and Western Union reported losses for the period, while Boeing Co. and Singer Co. recorded increased profits.

Revenue at Capital Cities-ABC Inc. for the quarter was $1.07 billion, compared with $267 million in 1985. The earnings and revenue reflect the operations of American Broadcasting Cos., which Capital Cities acquired in January.

For the first six months, earnings totaled $349 million ($21.63) compared with $69 million ($5.28) in the same period of 1985. Revenue in the first half totaled $2 billion compared with $501 million last year.Eastman Kodak Co. lost $12.2 million in the second quarter as its cost-cutting plan continued to incur unusual costs, a company spokesman said.

The loss is the second in three quarters for the 106-year-old company, which, until last year's final quarter, had not had a net quarterly loss in more than 50 years.

The net loss was in contrast with 1985's second quarter, when the company had a profit of $164.3 million (72 cents a share).

Sales for the quarter, thanks to strong performances from 35-millimeter and X-ray film in the photographic division, and plastic and fibers in the chemical division, were up 10 percent at $2.69 billion, compared with $2.46 billion for the same time last year.

The $167.8 million Kodak took for unusual costs in the quarter came from several items including trimming its work force by 10 percent and write-downs and write-offs for inventory and equipment. Unocal Corp., blaming lower fuel prices and higher interest costs from its takeover fight against T. Boone Pickens Jr., said its earnings plunged by 71 percent in the second quarter of the year and 65 percent for the half.

Unocal, based in Los Angeles, parent of Union Oil Co. of California, earned $34.6 million (30 cents a share) on revenue of $2.1 billion for the three months ended June 30, compared with the year-earlier period when it earned $120.4 million (83 cents) on revenue of $2.89 billion.

For the half, it earned $104.8 million (90 cents) on revenue of $4.38 billion, compared with $301.1 million ($1.89) on revenue of $5.68 billion a year ago. Boeing Co. reported an increase in its second-quarter profit on strong sales, particularly for a longer version of its 737 commercial jetliner.

Net income was $169 million ($1.09 a share) on $4.02 billion in sales. That compared with earnings of $136 million (93 cents) and sales of $3.37 billion for the same period last year.

Boeing President Frank Shrontz said that new orders for jets "are continuing at a high level." Singer Co. reported a second-quarter net income of $21.8 million (98 cents a share), up 79 percent from $12.2 million (61 cents) for the same period in 1985.

Revenue for the latest quarter was $417.5 million, up from $366.3 million in 1985, which has been restated for discontinued operations. Western Union Corp. reported a $9.5 million loss for the second quarter of 1986, despite $7.5 million in income from a discontinued operation and a one-time gain from that operation's sale.

It was the company's eighth consecutive quarterly loss. In the same period last year, the company reported a loss of $9.7 million. Western Union reported a $16.8 million operating loss for the quarter.