Visitors to China discover a hungering for more contacts with the West

''I'll never be the same after this visit,'' said an American from Washington State who found himself hard put to explain why. Yet that is how China seems to affect many visitors, both in terms of expectation and reality.

Perhaps it is partly the realization that the Chinese constitute one-fourth of mankind. This abstract perception comes alive with breathtaking vividness when one's bus is surrounded by what Washington wheat farmer Richard Deffenbaugh described as a ''solid wall of people'' - all curious, all friendly.

''If you have any humanity at all and look at these people,'' said William P. Gerberding, president of the University of Washington, ''you see how eager they are for exposure to Western science, technology, modernity.''

Such were the prevailing impressions of China a recent delegation from Washington State carried back with it: friendliness, a ''wall of people,'' and an eagerness for contacts with the West.

There was also a dimension to their trip that transcended any immediate commercial considerations. It is a dimension probably felt by almost every traveler to China since Marco Polo - an eagerness to have contact with a civilization so different from that of the West, with a people and territory so vast and yet so self-contained.

Such contacts can also spark indignation as when a couple of delegation members on a walk down from scenic, precipitous Qingcheng mountain and its Taoist monastery came across young boys and girls shouldering 100-pound baskets filled with coal. They were paid 90 fen - about 45 cents - for every hundred pounds they carried to the tourist facilities at the top of the mountain.

The indignation is directed against the poverty that necessitates such practices. Yet, from the children's viewpoint, where else could they earn such money? In one day, they can go up and down the steep five-mile trail three or four times. ''What time is it?'' asked a 14-year-old shouldering 120 pounds. When he was told it was 11 a.m. he cheerfully replied, ''Good, I still have time for three more trips.''

In China, one is never far from the basics - food, clothing, housing. Delegation members visited stores generally well-stocked with various consumer goods, and some of the women commented that there was much more color in women's and children's clothes than they had expected.

Yet the China of the streets of Chongqing, where men strain against carts loaded with goods to pull them up the hills on which the city sits, is a land where every orange peel, every scrap of wastepaper, every horse dropping, is carefuly picked up and used.

Paradoxically, in some of the factories the delegation visited, no one seemed to be working particularly hard. As one member commented there seemed to be no logical flow line - inventory and parts were ''scattered all over the place.''

At one factory that makes measuring instruments, however, there seemed to be meticulous attention to detail, and workers' hands and fingers moved with a sense of purpose. This factory exported one-fourth of its output to 29 countries around the world.

The tall young woman escorting some of the delegation members had graduated from engineering college just two years ago and had an infectious eagerness. When she could not answer a question she would promptly find a more senior engineer who could. ''I'm interested in everything!'' she exclaimed.

So the impressions of the delegation members as they visited communes, factories, universities, and cultural sites were mixed. On the one hand there was sympathy for people's efforts to better their lives, to move from poverty to a stage of being somewhat better off. On the other hand, would China truly succeed in reshaping its bureaucracy and modernizing its economy?

One bank president said he was surprised not by poverty, or by limits on speech, or by the general state of the factories he saw, but by the vehemence with which some people referred to the chaos and persecution of the Cultural Revolution years (1966-76). He felt that the policies of the present leadership, emphasizing economic incentives instead of sloganeering, were reasonably realistic.

But would Deng Xiaoping last? Is there significant opposition to the Dengist policies, and if so, around which issues would they crystallize? These were the questions he asked, Mr. Strong said.

Almost every Western visitor to China has asked similar questions. Deng Xiaoping himself, a short, peppery son of Sichuan and its fiery cuisine, has told visitors that questions about the stability of present policies do not surprise him: many Chinese express the same doubts.

One visit, however memorable, is insufficient to provide reliable answers. Repeated visits over the years will at least supply a basis of comparison. Members of the delegation said they returned to the United States with great goodwill and a more practical realization of the problems involved in trying to modernize so vast and poor a country.

''I'd like to come back in 10 years to see what progress they've made,'' said Bonnie Struthers, wife of the majority whip in the Washington State legislature.