The House yesterday approved, in a 201-to-198 vote, a Senate House conference report that sets a $498.8 billion targets congressional budget for fiscal 1979.

Many liberals who had voted for the House's version of the target budget last week defected yesterday, voting against the conference report because it contained more defense spending and less education and social spending than they wanted.

But House Democratic leaders were able to attract enough conservative Democrats to the budget to offset the liberal defections.

The House, unlike the Senate, has always had problems fashioning a federal budget that contains enough spending and a low enough deficit to attract a sufficient number of moderate and conservative Democrats.

House Budget Committee Chairman Robert Giaimo (D-Conn.) warned after yesterday's vote that if liberals form big cities "leave us because of some pique likey they did yesterday, they will push us into the hands of those whose price is to lower spending on social and urban programs."

In an interview, Giaimo said, "What if we had gone down yesterday? How would we have fashioned a new budget? Certainly with less spending rather than with more . . . If I were some of the liberals from the big urban areas I would make a reassessment of (my) position.

Last week the House passed its version of the budget by a similarly narrown 201-to-197 margin.

Among liberal Democrats who voted for the House budget lost week but against the conference report yesterday were Reps. Parren Mitchell (D-Md.), head of the House Black Caucus, David R. Obey (D-Wis.) and Elizabeth Holtzman (D-N.Y.). All three are members of the Budget Committee.

The Senate which has advocated higher defense spending and lower social spending than the House in recent years, easily passed the conference report by a voice vote late Monday night with few senators in the chamber.

In an act of seeming contradiction, only hours after passing the budget resolution yesterday, the House voted down a bill settling a ceiling of $849.1 billion on the federal debt in fiscal 1979, the same ceiling that was contained in the budget. The vote was 167 to 228, with 58 Democrats who voted for the budget disapproving the debt ceiling limit.

That means that each time the Treasury nears the limit on its borrowing authority, the House and Senate will have to consider whether to raise it, rather than passing a debt ceiling that will cover a whole spending year.

The target budget resolution, which serves as a guide to spending and taxing legislation over the summer, does not need presidential approval. Congress must pass a binding budget by Sept. 15.

The budget the House approved yesterday and the Senate approved Monday calls for spending $498.8 billion in fiscal 1979, which starts Oct. 1, and raising $447.9 billion in revenues. If the budget projections are accurate, the federal government will be in deficit by $50.9 billion in fiscal 1979.

President Carter's revised proposals for fiscal 1979 call for spending $499.4 billion. His proposed deficit had been $59.6 billion, but that will shrink to something closer to the congressional deficit because the president agreed to reduce the amount of tax cuts he wants in fiscal 1979 from about $25 billion to $15 billion.

But Office of Management and Budget officials said yesterday they cannot tell yet how much the reduction of tax cut will trim the president.

Because of slower economic growth than anticipated this year, the revenue estimates may be lower than projected in mid-March, an OMB official said.

OMB director James McIntyre said in remarks prepared for a speech in New York last night that while he is encouraged by the smaller budget Congress approved, some of the spending levels below the president's are illusory.

He said he thinks the administration's estimates of spending are better than Congress.