Pension fund managers, the guardians of retirement dollars for milliosn of American workers, are moving cautiously into new investment arenas, but the old standbys -- stock and bonds -- still make up the lion's share of pension fund portfolios.

When the bottom fell out of the stock market in the early 1970s, pension fund managers began to shift their investiments from equities to bonds -- which promised, it seemed, more stabillity. But in recent years, expecially in the past year, stubborn double-digit inflation and record-high interest rates sent the bond markets off on a roller coaster that resembled the worst days of the stock market.

"Pension fund managers have been doing a lot of soul-searching trying to figure out what other investments could be used to reduce volatility. They've been searching for alternatives," according to Charles Salisbury, of T. Rowe Price Associates Inc., one of the nation's largest money managers.

Those alternatives include investing in real estate and stocks of companies that are not traded in the United States.

"Anyone who owns a house understands the lure of real estate. The profits to be had are reminiscent of the late 1960s in the stock market. People are willing to accept even a 5 to 6 percent return on a lease, because of the residual value of the building itself," said.

Fast-growing econimies such as Hong Kong or Malaysia are "appealling" countries in which to buy stocks, as are those in which currencies are stable, such as Switzerland or West Germany, he said.

Still, Salisbury said, probably not much more than 2 or 3 percent of the $300 billion that private pension plans have to invest are tied up in foreign securities such as Treasury bills or money market mutual funds. Funds often hold their resources in "cash" while the search for better investments.

Pension funds, which shunned the stock market from 1973 until 1978, are rediscovering equities today. In the early 1970s, as much as 75 percent of pension fund assets were invested in stocks, with the rest in so-called fixed-income securities like bonds.

By 1978, that ratio had been narrowed to about 50-50. But since then, convinced that stocks were undervalued, pension funds gradually have been increasing their stock purchases. The funds have concentrated on two areas: companies in the natural resource field and high-technology stocks.

At the end of August, stocks made up 58 percent of the portfolios of private pension plans, with bonds at about 40 percent and real estate 2 percent.

"Funds have been looking for value in the companies they invest in," and they see value in natural resources, according to George Connell, first vice president of Drexel Burnham Lambert In., a big brokerage frim that manages pension funds.

Instead of buying the resources themselves, the pension funds by the companies that own the resources, such as oil companies or paper companies. At the same time, the pension funds are shifting their money out of consumer-oriented stocks such as retailers.

"Look at Standard Oil of Ohio. With the stock at 66 1/2 [that is, it costs $66.50 a share], the company controls reserves that are valued from $2200 to as high as $1,000 a share. Funds are looking to buy natural resources at a big discount by purchasing oil stocks," Connell said.

In recent months pension funds have been buying stocks in gold mining companines, something they would not have considered just a year ago because of worries about employe reactions to investing retiremnt dollars in South African companies, according to one expert.

But gold-mining stocks have been perfomring so well that investment managers slowly have invested millions of dollars in mining stocks in a variation on the theme of purchasing natural resources by purchasing the company that owns them. Like oil in the ground, the value of the gold in the mines has risen sharply in recent years.

One of the major vehicles for investing in gold stocks is American South Africa, a holding company traded on the New York Stock Exchange that is like a mutual fund -- it invests in stocks of many mining companies. "It is a way of buying and at the same time diversifying," according to one expert. i

Pension fund managers look at high-technology companies, such as Raytheon or Teledyne, in much the same way they view natural resource technology stocks, the funds are buying know-how instead of resources.

Traditionally, pension funds have been averse to taking risks with their investments. The hundreds of billions of dollars are there to provide working citizens with income after retirement. That fear of taking big risks remains today, although rapid inflation has so eroded the value of many pension fund investments that boards of trustees that oversee the funds are freeing up portions of their assets for investment in riskier but potentially more profitable areas such as growth stocks.

"It depends to a large degree on the company. A company with a mature work force and large unfunded liabilities needs a much more 'plannable' outlook than a younger company with a young work force. The younger companies can afford to be more aggressive," according to Salisbury of T. Rowe Price.

Increasingly, the pension funds themselves are deciding the broad management of their money, then farming out particular investment functions to different managers. The general Motors Corp. pension fund, for example, has 11 different managers, each of whom guides the investment of some portion of the fund's $4.5 billion in assests.