Try flipping the carb over and draw filing the base -- if it isn't flat, you will find out quickly, and should be able to get it flat fairly easily. Quadrajets are notorious for warping, every single one I've handled had to have the base flattened (especially if someone used a chisel to remove the idle cap).

If it is really warped, junk it and get another one, or do a replacement. You will have trouble finding a Q-jet or Holley small enough to do a direct replacement, I'm afraid -- you won't need more than 350 cfm, if that.

Check to make sure the throttle body is secure on the venturi block, too -- a leak here will drive you nuts.

Don't forget to check for the other "obvious" vac leaks before condeming the carb -- there are two vac lines to the carb, and the vac pulloff on the carb can leak, too. A bad manifold gasket can cause serious vac leaks.

Most of the usual vac accessories (brake booster, AC, locks) run off a pump on the head, I think, on this car.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!