The US economy appears to be growing faster than many economists had expected , triggering concern about higher inflation and tighter credit conditions. A flurry of new government statistics underscores the economy's surprising strength. In April, industrial production jumped 1.4 percent, while seasonally adjusted housing starts spurted 19.3 percent. As a result of the increased activity, excess capacity in United States factories shrank. And in the first 10 days of May, new-car sales soared 25.5 percent from the same period last year.
''We are getting faster growth than people anticipated,'' says Steven Wood of Chase Econometrics. Both home construction and business investment have been more robust than anticipated, analysts say.
Earlier this year Chase analysts thought the inflation-adjusted gross national product would be 2.9 percent in the April-to-June period. Now the firm expects the GNP, the value of goods and services produced in the economy, to grow as much as 3.5 percent in that period.
Other forecasters now are expecting even faster growth for the second quarter. Data Resources Inc. predicts that real GNP will grow as much as 3.8 percent this quarter, and the Georgia State University Economic Forecasting Project sees growth of 5 percent. In the first quarter, the GNP grew 8.3 percent.
This is one time when more is not necessarily better, economists say. The faster-than-expected growth is pushing the economy closer to the limits of its productive capacity, threatening the creation of inflationary bottlenecks. In April, for example, 82.3 percent of the nation's manufacturing capacity was in use, up from 81.2 percent in March.
''We are at the level (of capacity utilization) where we start to see demand pressures increase,'' notes Georgia State economist Donald Ratajczak.
A typical capacity-utilization rate hides a wide range of factory-use data. Some industries such as rubber and plastics, electrical machinery, and paper products are already operating at more than 90 percent of capacity.
The inflationary effects of greater factory utilization are somewhat offset by the ''tremendous amount of excess capacity that exists overseas,'' notes Data Resources vice-president Roger Brinner. Those idle factories help hold down US companies' prices where transportation costs are not prohibitive.
And so far, overall inflation indexes have been well behaved. In April, for example, producer prices were unchanged. ''In the aggregate number you don't see it, but in the detailed components (of the indexes), inflation is clearly beginning to show up,'' Chase's Mr. Wood says.
Inflationary pressures typically rise as a recovery goes on. Wage demands increase, productivity gains slow down, and factories work closer to their full capacity. Chase expects the consumer price index to end the year in the 5 to 6 percent range.
A key concern for both investors and politicians is that the Federal Reserve Board will react to the faster-than-expected growth by tightening down further on credit when its policymaking Federal Open Market Committee meets May 22.
As long as economic growth remains stronger than expected, ''there is no room for the Fed to ease and there is the possibility of further tightening,'' says Ben Laden, chief economist at T. Rowe Price Associates Inc.
The Fed's recent apparent tightening of the supply of credit triggered sharp criticism from the Reagan administration and slumping prices in the bond market. Because a bond pays an investor a fixed rate of interest, bond prices move down when interest rates climb.
At his press conference Monday, however, President Reagan softened his administration's attacks on the Fed. ''They (the Fed) do as well as they can,'' he said.
The political impact of rising rates was underscored Tuesday when Senate Finance Committee chairman Robert Dole (R) of Kansas said that each one-point rise - or even a half-point rise - could cost the Republican Party a Senate seat. And a hike of two or three points in banks' prime, or benchmark, lending rate could cost President Reagan the election, Senator Dole said.
At the moment, Fed-watchers believe that the monetary authorities will defer additional action at their meeting next Tuesday, so they can see how recent tightening moves have affected interest-sensitive industries like housing and autos.
The Fed ''is going to wait and see,'' says Jerry Jasinowski, executive vice-president of the National Association of Manufacturers.
But if fast growth continues, many economists believe the Fed will clamp down on credit a bit more.
In the housing sector, experts already are predicting a marked slowdown from April's rapid housing-start pace. Government statistics show that building permits slipped 0.1 percent in April. And a National Assocation of Home Builders survey of members found that their expectations for sales were ''sharply down'' in May, says Michael Sumichrast, the NAHB's chief economist. He sees starts falling from their 1.963 million seasonally adjusted annual pace in April to an average of 1.6 million in the second half of 1984.
The overall economy is also expected to slow in the second half, as the effect of recent interest rates hikes takes hold and as companies cut back on efforts to build inventories. Real GNP growth in the third and fourth quarters should average 3 percent, Mr. Jasinowski says.