The executive committee of Spain's ruling party proposed an economic specialist today to become premier following the surprise resignation yesterday of Adolfo Suarez.

Choice of Deputy Premier Leopoldo Calvo-Sotelo, 54, proved divisive, with eight of the 35 members of the Union of the Democratic Center's ruling body walking out rather than endorse him.All were from the conservative wing of the party that Suarez put together to assume the premiership in 1976.

King Juan Carlos is expected to continue consultations with parliamentary leaders this weekend and the executive of the ruling party is expected to meet again before formal designation of Calvo. He then would face approval by the 350-member Congress of Deputies, in which the party holds 167 seats.

At the center of what several Spanish commentators have called the gravest political crisis since the death of dictator Francisco Franco in 1975 is speculation over the reason or Suarez's abrupt decision to quit. Statements by the Defense Ministry saying the armed forces played no part were greeted with skepticism in political circles. The military is thought to have questioned Suarez's approach to the issue of separatist Basque violence.

The king, whose consitutional role in the political crisis normally is pro forma, was placed in a delicate position and was reported to be concerned about the division within the ruling party over the choice of Calvo.

Reflecting a broad concern for consensus in the congress, Socialist Party leader Felipe Gonzalez said as he left the royal palace that his party was prepared to enter a coalition government if necessary. He added that the party, with 121 seats, would have preferred to await new elections.