The Ultimate Guide to Holley Carburetors
Everybody has a least carburetor, but not everybody knows how to tune them, so we're giving you a bunch of charts, graphs, advice and tips so you'll know just about everything you'll need to get your carburetor tuned right.
Carb Main Body
(A) Idle air passage:
Air from the idle air-bleed enters the metering block here.
(B) Accelerator pump discharge passage:
Fuel from the accelerator pump enters the main body of the carb here and travels up to the squirter.
(C) Fuel bowl vent:
This vent places atmospheric pressure on the fuel in the float bowl.
(D) High-speed air-bleed passage:
This is where air from the high-speed air-bleed enters the metering block.
(E) Booster venturi inlet: Emulsified fuel from the main well enters the booster through this passage.
(F) Power valve vacuum well:
Intake manifold vacuum is present in this cavity. When the throttles are opened and vacuum drops off in this well, the power valve opens.
(G) Timed spark port:
This hole delivers manifold vacuum only after the throttle is opened past curb idle. This is normally the outlet port for vacuum advance.
(H) Idle transfer slot to discharge:
This port delivers fuel to the idle transfer slot in the throttle body that is uncovered under light throttle.
(I) To curb idle:
Idle fuel enters here from the metering block to the curb idle discharge point on the throttle body.
(J) Auxiliary air:
This hole is used only with an auxiliary idle air-bleed circuit.
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