Zheng Lianqun never saw his American father. His frightened Chinese grandmother burned the only picture when the Korean War broke out.

But his light skin and freckles betray his heritage, and for two years he has been selling his blood to finance desperate search for his past.

Huang Yi, a smiling auto mechanic with less obvious Caucasian features, only knows that his American father had a dragon tattoo on one arm and a name sounding like "Ozzie." Huang has come 400 miles only to discover the Chinese Army guard will not even let him inside the American Embassy to try to find out more.

Zheng, 32, and Huang, 30, are just two out of thousands of Chinese to whom normalization of relations between the United States and China means much more than a shift in global polities. The new U.S. Embassy here, and its consulate in Canton, are being deluged by Chinese who have some American connection that they have kept hidden for years. Now they se a chance to solve a mystery of their lives across the Pacific.

They want to go to the United States, which despite years of communist accounts of economic crises in the West still retains the sort of image that led the 19th century Chinese to give San Francisco the name still used here, Jiujinshan "Old Mountain of Gold." U.S. officials say unexpected numbers of Chinese are beginning to inquire about Social Security and other U.S. government benefits they feel entitled to by some past connection.

Zheng, a bricklayer, has made at least 20 trips to Peking and to his mother's home in Shangdong. He has written 20 letters to the United States, including one to President Carter, and sold his blood at least nine times to various Chinese hospitals to raise money for his search for his father. The man's name, he thinks, is Louis George or George Lewis. The Chinese put family names first so he is not sure. The man served in the transport battalion of the 1st Marine Division in Tianjin (Tientsin) from 1945 to 1946, when he married Zheng's mother, a 20-year-old jute millworker named Li Shuzhen, Zheng says.

He says his mother's relatives tell him his mother succeeded in getting a U.S. immigrant visa in May 1947 and followed her husband to San Diego, putting Zheng up for adoption because she decided the trip would be too hard on a 3-month-old baby. She promised to send for him later.

Her mother in Shandong received a picture of her with her American husband and two more small children about three years later. The husband wrote his mother-in-law from Korea, but she burned the letter and no more came.

Beginning in 1977, Zheng went to The U.S. liaison office 10 times over a year before he got a letter from an embassy official that allowed him to actually enter the building. He has been back nine times since, with embassy officers initiating several unsuccessful searches of military record centers baack in the United States. Embassy officials have told him it is hopeless, but Zheng refuses to accept this.

Embassy officers estimate they receive as many as 20 letters a week from Chinese seeking information about lost relatives that eventually might produce visas for them to the United States.

"This is one of the few cases we just haven't been able to trace," a spokesman said.

Zheng estimates his father would be about 72 now, and his mother 54. A friend of the mother's who was an interpreter for the American introduced them in 1946, neighbors told Zheng after he felt at ease enough about U.S.-Chinese relations to begin to inquire.

"I had it in my head before. Other children would tease me and call me a 'big old Yankee' because of the way I looked, but I thought it was a joke, because I had a Chinese mother and father," Zheng said. "Then in 1972 when the Shanghai Communique was published [reestablishing official Sino-American contacts] my adoptive mother and people who knew came and told me I was mixed blood, my mother was Chinese and my father American."

Zheng began to ask questions. With the cooperation of the Tianjin public security office, which takes special interest in reuniting lost relatives, he found a woman who had been a close friend of his mother.

By 1977 Zheng decided to launch a full-scale search for more information that would allow him to find his parents and go to the United States. He no longer had time for bricklaying work at his construction company. He lived on disability checks received by his wife and what he could get selling blood to local hospitals once every three months, about $30 for two-thirds of a pint. He showed several puncture marks on his arms.

Huang met Zheng outside the U.S. Embassy. He took a 20-day leave from his company in Shandong to try to gather more information about the man his mother, Jin Lin, said she married in 1948, before the man returned to the United States on a merchant ship. Chinese guards control access of all Chinese to the U.S. Embassy annex building where visas are issued. They will not let Huang enter until he has received in the mail some letter from an embassy officialhe can show as proof he has business there.

Like Zheng's grandmother, Huang's mother decided the rabid anti-American propaganda of the Chinese government meant she should keep her U.S. connection a secret. She said she burned the only picture she had of Huang's father during the Cultural Revolution in the late 1960s and did not tell her son the true story until 1974.

The more time Zheng devotes to his obsession, the more he cuts himself off from Chinese society, without any real hope of finding the American past he seeks. He was denied admission to the Chinese Air Force and is no longer allowed to read the special party bulletins circulated in his construction team because of his assumed but unproved foreign connection.

The embassy here, which sometimes has 100 persons each morning crowding its small reception area, has not seen the last of him.

"I am of American blood, and I think the U.S. government has the responsibility to help me," he said.