Front Vacuum Break: Notes

NOTE: This adjustment is performed using the choke angle gauge, see procedure at beginning of ADJUSTMENTS .

Using an outside vacuum source of at least 15 in. Hg, seat front vacuum break diaphragm. See Fig 1.
NOTE: Plug purge bleed hole (if equipped) with masking tape. Hole is found in end of diaphragm.
Close choke by pushing up on choke coil lever or vacuum break lever tang. Hold choke closed with a rubber band.
Bubble on angle gauge should be centered with specified degree mark opposite pointer.
NOTE: Certain earlier models will have tamper-proof plugs over the adjustment screws. To gain access to adjustment screws, remove vacuum break bracket from carburetor. Carefully grind off plugs over adjustment screws and replace vacuum break diaphragm.
To adjust, turn vacuum break adjustment screw in until bubble of choke valve angle gauge is centered.

Fig 1: Adjusting Front Vacuum Break
Courtesy of GENERAL MOTORS COMPANY