Back on Holley carbs and their Calibrations today.
I will be posting up a few "calibration bits of info" today on 4150/4160 Holley Carburetors.
The info would also apply to Holley 4412 2-BBL carbs.
a) Some Holley Carbs have two "Flat Top Plugs" on the top surface of the Metering Block. Others have "Cup Plugs" in the same locations.
The "Cup Plug" Metering Blocks are more of a Performance Metering Block vs the "Flat Top Plug" Metering Blocks.
The "Flat Top Plug" configuration means that there is an Emulsion Tube extending inside the Idle Well to remove volume in the Idle Well and make the circuit more responsive. Great for Driveability, not so good for High Performance applications. Avoid these metering blocks.
b) The Anti-Syphon Bleed also called the "Kill Bleed" in the metering block helps to purge hot vapors from the Idle Circuit and also eliminate syphoning of fuel from the Idle Well. It is typically fixed in size and location.
c) The "Idle Feed Restriction", (also called the "Idle Jet"), is mounted low in the metering block, close to the Main Jets. It is in that location, for a reason. That reason is the "IFR" or "Idle Jet" is submerged in LIQUID FUEL and continually meters that Liquid Fuel. This is the PRIME Idle Fuel Calibration Circuit component.
Holley revised this circuit and moved the IFR to a High Mount Location where it now metered Fuel and Air on later Metering Blocks.
Bad Mistake. Most good carb modifiers put the IFR back where it belongs in the original low mount location.
d) The Idle Air Bleed is the Prime Air Bleed for the Idle Circuit and is located in the upper portion of the Main Body in most carbs and located in the Metering Block Idle Cross Channel on some Modified Carbs where the Carb Guru does not want people knowing what the orifice size is for the specific carb. The Bowtie Guys had some carbs made that had a 'alternate' idle air bleed (in the Air Horn Ring location) but this is not a common location.
e) Some Holley Carbs used a Idle Well Tube (mentioned earlier) that bleeds air into the Idle Well Channel. In this case the bleed air mixes with the idle fuel and creates a homogeneous fuel/air mixture prior to exit thru the idle discharge port hole ot the Transfer Slot location.
More carb info another time.
Tom V.
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"Engineers do stuff for reasons" Tom Vaught
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