The administration insisted yesterday it has preserved 90 per cent of proposed energy savings as the House Ways and Means Committee completed the first round of tentative votes on tax parts of President Carter's energy plan.

Assistant Secretary of Treasury Laurence Woodworth, former chief tax adviser to the committee who sat through the 2 1/2 weeks of markup answering members' questions, made the estimate and predicted the President will do as well in the final round of voting The first round was to guide the staff in preparing a draft bill which the committee began considering yesterday afternoon.

In its first actions on the draft, the committee rejected an amendment to out the gas guzzler tax on big cars and another one to strengthen it.

This is where the President's bill stood at the end of the first round:

The standby gasoline tax that could have gone to 50 cents a gallon in 10 years was rejected, as was a price-reducing tax rebate on purchase of small high-mileage autos. The proposed tax on gas guzzlers was delayed one year to 1979 and the miles-per-gallon standards auto makers must meet to avoid the tax relaxed after that. The gasoline tax for noncommercial motorboats and private planes was increased.

By a one-vote margin, the committee tentatively approved a tax credit for home insulation, and it approved another for installing solar and wind energy equipment.

A three-stage tax on the wellhead price of crude oil to force up the price to world levels as a major consumption deterrent was approved but would expire in 1981 when price controls expire. The revenue would be rebated to taxpayers next year. Congress must then decide what to do with the money in future years.

Carter's big oil saving program - 3.3 million of the 4.5 million barrels of oil a day he hopes to save by 1985 - was to come from inducing industry and utilities to convert from oil and natural gas to coal. The committee voted to exempt from a tax on continuing use of gas and oil certain processing plants where use of coal would damage the product and voted lower tax rates than the administration wanted. It also approved a tax credit program to help pay for conversion to coal.

As the second round of voting began yesterday, Rep. William M. Brodhead (D-Mich.) offered an amendment for the auto industry that, according to administration figures, would in effect have delayed the gas guzzler tax until 1982.

Brodhead's amendment would have suspended the tax until one year after the average of the industry's entire auto production fell below the required miles-per-gallon standard.

The administration strongly opposed this on grounds it meant auto companies that had dragged their feet and are still making big cars would get a free ride on companies that have switched to small cars. It was rejected, 22 to 14.

Rep. Charles A. Vanik (D-Ohio) offered an amendment to tighten miles-per-gallon standards about halfway back up to the original administration levels and lost, 15 to 9.

Brodhead explained that his main concern was to exempt from the tax in 1979 one Chrysler model, which he said the industry told him will be the only 1979 model produced in the United States which would be unable to meet the committee's standard of 15 miles per gallon.

Brodhead said the car would fall one mile short and offered a second amendment reducing the level tax-free cars must meet in 1979 from 15 MPG to 14. Brodhead said that if the auto industry was not able to meet mileage standards after 1979 he would support stiff taxes against them.

Rep. Martha Keys (D-Kan.) offered a substitute that would delay the gas guzzler tax until 1980 but then incorporate the stiffer standards proposed by Vanik.Woodworth said Keys' proposal would increase energy savings in the committee bill by 1985 to about 185,000 barrels of oil a day, compared to 200,000 in the administration proposal. The committee quit for the day before voting on the keys proposal.