The House is gearing up for a heated debate today over a Commerce Committee authorization bill beginning legislative efforts to determine Amtrak's future during the next three years.

A flurry of amendments, lobbying efforts and general confusion is being roused over a threatened 43 percent cut in route service proposed by Secretary of Transportation Brock Adams last January that will go into effect Oct. 1 unless Congress acts.

But the highly political ramifications of route restructuring and the flight to revitalize Amtrak are prompting a slew of self-interest issues.

The bill was brought by the House subcommittee on Transportation and Commerce, which is headed by Rep. James J. Florio (D-N.J.). The measure proposes increased funds for equipment and route cutbacks that are about half those urged by the administration.

The bill's formula approach calls for 150 passenger miles per train mile for each route and an "avoidable loss" for each passenger mile of seven cents or less. The bill has 65 cosponsors.

But because of recent increased demand for rail service, Rep. Albert Gore Jr. (D-Tenn.) and Rep. Wyche Fowler Jr. (D-Ga), along with 70 cosponsors plan to tall for a year-long moratorium - keeping all current trans - and to study the existing systems.

This week, however, Florio relayed a letter from Adams to a group of reporters indicating the secretary would recommend that President Carter veto legislation freezing Amtrak service.

The veto would put the 43 percent cut into effect automatically.

But Gore staff member Roy Neel called the move a "congress into passing the Florio bill.

Meanwhile, Rep. Edward J. Stack (D-Fla.) plans to propose a merit ranking of route service to keep Amtrak from determining arbitrarily or politically which trains continue.

And Rep. Harley O. Staggers (D-W. Va), chairman of the House Commerce Committee, is expected to reveal information from one of several documents being circulated that disputes Amtrak's cries for route cuts and the need for more cars.

One such report, said to be circulating among Amtrak officials, shows that the company has enough equipment to handle the present system, according to a DOT source.

Another report cites some 500 cars being rebuilt or repaired - some requiring only a repair on dining car grills - that could be on line within a year at a cost of $100,000 to $200,000.

Amtrak, which has suffered from poor track, antiquated cars and the need to cut out money-losing routes, admits that a memo to that effect was written.

But John Jacobsen, an Amtrak spokesman, explained that despite the total number of cars in service and being repaired, the company "does not have the capability of operating the system adequately" because of the need for repairs.

Much of the controversy over Amtrak was raised by the Carter Administration's January proposal, which was estimated to save $1.4 billion over the next five year but cut service along 12,000 miles of track affecting about 2 million riders.

Since then, ridership has boomed, partly because of gasoline supply problems. From a base of 16.6 million passengers in 1972, service reached 18.9 million in 1978, and it is estimated that it will hit 20 million this year, a 6 percent increase.

In May alone, 750,000 passengers were turned away while another 5 million were unable to reach Amtrak reservation telephone numbers.

The surge prompted Adams to agree to $75 million of additional funds for Amtrak. The Florio plan estimated an annual budget of about $866 million, close to DOT's revised proposal.