Brussels bourse favors the bulls

Stock market prices in West Germany, Britain, and some other West European nations have been rising heartily in recent months. So have stock prices in Belgium, but Rene Deweeck, head of the research department at Banque Bruxelles Lambert, sees a significant difference.

Institutional investors from the United States have been putting large sums into the bourses, or stock exchanges, in London, Amsterdam, and Frankfurt, but not in Brussels, he says.

Stock prices in Belgium rose some 40 percent between June 1981 and December 1982, plus some 22 percent this year. But this is because of the improved outlook for the Belgian economy and a new tax break for newly issued Belgian stock.

Mr. Deweeck describes this as ''a very sane improvement'' and predicts a total rise in the stock price average this year of about 40 percent -- ''as long as there is no major change in politics.''