3/4" accelerator pump cup is used in large bore 2 barrel Rochester 2G, 2GC, 2GE and 2GV carburetors.
Information for Rochester Quadrajet carburetors only:
Larger pump cup can be retrofitted in Quadrajets for racers that need additional accelerator pump volume. Replaces the original diameter Q-Jet pump cup on the Q-Jet pump plunger assembly.
The Rochester Quadrajet accelerator pump well located in the main body casting MUST be custom machined to .730" to accept this larger pump cup.
Instructions when replacing Rochester accelerator pumps:
It is very important that the accelerator pump bore is completely smooth. Today's fuels with ethanol have less lubrication and demand super smooth pump bore surfaces. Polish pump bore with crocus cloth as required. Rough pump bore surfaces will cause pump cup to stick to bore and tear or dislodge from plunger assembly.
Do not allow carburetor cleaner come in contact with pump assembly.
Coat outer edges of pump cup with a light coating of grease, if pump bore is not submerged in fuel.
Long term vehicle storage:
If vehicle is dormant and fuel bowl is allowed to go dry, pump cup has a much higher chance of sticking to pump bore. If bowl has run dry, fill fuel bowl with fuel before pumping accelerator pump assembly.
Additional recommended items:
Replacing the accelerator pump requires the removal of the air horn/bowl cover, it's always a good idea to have an extra set of air horn/bowl cover gaskets on hand to replace a ripped or worn gasket.