Jerry is right...the plunger is your power piston. He also made mention of a really important fact. The important gasket hole will be the one between your manifold spacer and the throttle body of your carb. The gasket provided in most rebuild kits doesn't have the proper hole punched and you don't get vacuum to the power piston as a result. Also...back late summer I did a lot of work on these carburetors and posted all of it. If the air horn is warped (and it probably is) you may have loss of vacuum which will cause the power system to not work correctly.
Here is an image of your vacuum passage hole. And here is an image of the gasket you'll get in most rebuild kits. You can see why it doesn't work. Your power piston will never get pulled up off the power valve ball and you will run as rich as possible all the time.
~ Jon 1952 1/2 ton with 1959 235 | T5 with 3.07 rear end
