There are two check valves per accelerator pump circuit in the Holley. One is a rubber umbrella inside the pump chamber (if a newer carb) or a ball retained by a brass bail if an older carb. This works as a one-way valve (along w/the under squirter check) to allow fuel to go out via the accelerator nozzle, and fuel to enter to refill the pump as the pump returns after a shot.
Then, under the squirter there's another needle valve or ball.
The umbrella just gets replaced, the ball and bail can have the seat re-formed by carefully tapping a used check ball into the seat. Same thing for the under squirter check, if needed.
Last edited by cobalt327; 07-12-2010 at 06:46 PM.