An American congressional delegation visiting Peking has discussed with Chinese officials plans to help modernize the Chinese Air Force F8 fighter plane, officials said today.

The five-member congressional delegation, headed by Sen. Orrin Hatch (R-Utah), was to inspect the F8 factory at Shenyang in northeastern China, but after waiting for some time at the Peking airport the flight to Shenyang was canceled because of bad weather. The delegation is to depart Friday, and the visit could not be rescheduled.

Reached by telephone at a Peking hotel last night, Hatch, a member of the Senate's Select Committee on Intelligence, said he could not comment on what would have been an unusual visit to the factory. Other sources said U.S. defense delegations had visited it but this would have been the first congressional group to do so.

U.S. defense specialists are currently talking with the Chinese about ways of modernizing the Chinese-made high-altitude interceptor, by making it more versatile through the addition of U.S.-made avionics, or electronic devices, an official here said.

China has copied its fighters from Soviet MiGs. The F8, China's most advanced, is described by "Jane's All the World's Aircraft" as drawn from the MiG23. Its twin Chinese engines are said to leave it relatively underpowered. The Soviet prototype is said to have been provided by Egypt in 1976.

The group met yesterday with Hu Qili, a Politburo member considered to be one of China's rising political stars, as well as with Foreign Minister Wu Xueqian and Chinese defense and intelligence officials.

[In Washington, Pentagon officials said the sale of avionics to China by U.S. defense contractors, under the supervision of the U.S. Air Force, has been under discussion for some time. They declined to comment on the status of the avionics sale but other administration officials said agreement was likely to be reached "in the early part" of this year.]

In a dispatch from Washington last week, the Far Eastern Economic Review, a Hong Kong-based weekly, reported that the Chinese aircraft would be equipped with integrated navigational and fire control systems that would give them all-weather capability.

McDonnell Douglas, Boeing, Grumman, and Northrop are among the contractors that would be providing the components, the magazine reported.

China has an estimated 5,300 combat aircraft but virtually all are considered obsolete when compared with Soviet or U.S. capabilities.

American defense sales to China are a sensitve issue and the United States and China have moved cautiously in developing defense relations over the past several years. Late last year, the Reagan adminstration decided to make the first offer of a government-to-government military sale, to include as much as $98 million worth of technology and equipment to help modernize China's production of artillery shells.