In a major realignment of European currencies, Common Market finance ministers agreed today to raise the value of the West German mark and the Dutch guilder by 5.5 percent and lower the value of the French franc and Italian lira by 3 percent within the European Monetary System.

The accord, which followed eight hours of tough bargaining by the ministers meeting in Brussels, represents the largest change in currency parities since the inception of the system in March 1979. The monetary system was created to buffer European currencies against fluctuations in the dollar and promote financial discipline among Common Market countries.

One of the factors influencing the change was the recent rush of international money from the dollar to the deutsche mark. The recent dramatic drop in the dollar against the mark has reflected international doubts about the Reagan administration's economic plan and revived confidence in Bonn's economy as a result of an improvement in West Germany's balance of payments position.

A weaker dollar carries both good and bad news for the U.S. economy -- bad because it means more expensive imports, which add to inflation, but good because it means cheaper U.S. exports, which spur some American industries.

The revaluations had been anticipated for weeks, and the leak to an Italian newspaper last week that the currency adjustments were imminent sent the value of the dollar down in European foreign exchange markets Friday.

After the changes were announced today in a communique, West German Finance Minister Hans Matthoefer told reporters the agreement would increase the strength of the mark. He added that expectations in the United States were for a strong rise in the mark's value against the dollar.

The dollar has fallen dramatically against the deutsche mark to a closing value Friday of DM 2.28, from a three-year high just six weeks ago of DM 2.58.

The European Monetary System was engineered largely by West German Chancellor Helmut Schmidt and former French president Valery Giscard d'Estaing to foster a "zone of monetary stability" in Europe at a time when European confidence in U.S. economic management under former president Jimmy Carter was low. The system, despite certain drawbacks, has been more successful than even many supporters had expected.

Since its inauguration 2 1/2 years ago, the system has had only one modest general realignment, in September 1979.

The system links the currencies of eight of the l0 European Economic Community member nations -- excluding Britain and Greece -- in a joint float against other world currencies.

Causing much of the pressure for today's realignment was the contrast between French and German economic policies following last May's election of French President Francois Mitterrand.

While West Germany has been keeping its monetary policy tight and instituting austerity measures to restrict federal borrowing next year, Mitterrand's Socialist government has moved to create new public sector jobs and legislate other measures to cut unemployment.

West Germany and France had an interest in delaying adjustments in their currencies -- France because a devaluation of the franc would be a blow to its national pride, and Germany because an increase in the mark's value would make German exports more expensive and thus threaten the country's hope of pulling out of the recession soon.

French Finance Minister Jacques Delors told reporters the steep difference between inflation rates in France and West Germany made the realignment a "collective and inevitable step." French inflation is running at 13.7 percent a year, compared to 6.6 percent in West Germany.

Delors said today's meeting was called at the joint initiative of France and West Germany. It preceded a scheduled meeting this week between Mitterrand and Schmidt.

"We could not wait any longer because of the movement of the dollar and the level of interest rates in the United States," Delors said. The high U.S. interest rates prompted the French to push up their own, thus crimping Paris' budgetary expansion plans.

Much of today's bargaining involved which currencies should be changed and by how much.