The House Social Security subcommittee gave final approval to a $165 billion Social Security rescue package on a 7-to-4 party line vote yesterday, with Republicans objecting that the plan relies too much on taxes and revenues from the Treasury and not enough on structural changes.

Just before approving the bill, the subcommittee rejected by the same party-line vote GOP moves to eliminate a large portion of the long-range deficit by raising the retirement age from 65 to 66 or 67 in the next century. Instead, it adopted a Democratic amendment raising taxes slightly and reducing the basic benefit somewhat in the next century.

Rep. Willis D. Gradison Jr. (R-Ohio) said he and at least one other Republican "would have voted for the bill" had the age-66 amendment been accepted and less reliance been placed on borrowing from general Treasury revenues in case of a financial emergency.

The measure goes to the full Ways and Means Committee, which is to take it up Tuesday or Wednesday.

The final bill would provide the full $165 billion recommended by a special bipartisan presidential commission to help the system meet a short-term funding crisis. In addition, it would close the entire long-range funding deficit, estimated at 2.09 percent of taxable payroll.

The major issues yesterday were the long-term deficit and a "fail-safe" mechanism in case of a cash crisis.

Commission recommendations previously adopted by the subcommitte had cleared up two-thirds of the long-term deficit, leaving the rest--equal to 0.68 percent of payroll--to be worked out.

Democrats caucused in the office of subcommittee chairman J.J. (Jake) Pickle (D-Tex.) with Ways and Means Chairman Dan Rostenkowski (D-Ill.) and then backed the compromise long-range plan, sponsored by Rep. Beryl Anthony Jr. (D-Ark.).

The basic benefit received by the average newly retired worker in his first monthly check at age 65 would be reduced from the current level of 42 percent of previous monthly gross pay to 40 percent. The change would apply only to future retirees and be phased in from the year 2000 to 2008.

In addition, the Anthony plan would raise the tax on employers and employes by 0.24 percent each in the year 2015. It is currently 6.7 percent each and scheduled to rise to 7.65 percent in 1990.

These changes would eliminate the remaining 0.68 percent long-term deficit, Anthony said, with about three-fifths of the impact coming from the formula change and the rest from the added tax. Democrats said this was an attempt to meet objections from some conservatives that the package relied too much on tax increases and not enough on benefit curbs.

However, Rep. Claude Pepper (D-Fla.), who opposes further benefit curbs, said he would try to change the provision on the floor to substitute only taxes for the Anthony provision.

Reps. Bill Archer (R-Tex.) and William M. Thomas (R-Calif.) offered but lost on amendments to substitute for Anthony's provisions an increase in the retirement age to 66 or 67 or much larger cuts in the long-range basic benefit.

Republicans also objected to borrowing from the Treasury as a fail-safe measure, even under a provision requiring congressional assent to a repayment plan.

The rescue package's key provisions would tax half the Social Security benefits of higher-income recipients, bring new federal workers under mandatory coverage, delay the 1983 cost-of-living adjustment for six months, raise the tax next year from 6.7 percent to 7 percent and increase taxes on the self-employed.