So in the past we:
1) Compared Throttle Plate Machining between "2 Corner" Idle Circuits and "4 Corner" Idle Circuits.
2) Discussed the Throttle Plate Numbering system Holley uses for their carbs Double Pumper and Vacuum Secondary: Example:
Vacuum Secondary 750 and 780 carbs typically have #172 Primary Blades and #173 Secondary Blades.
Double Pumper Carbs from 650 cfm to 800 cfm
the same throttle blades for the Primary and Secondary sides of the carbs. The Blade Diameter is 1-11/16" Blades in all 4 locations.
The 850 CFM #4781 Carb uses 1-3/4" Throttle Blades in all 4 locations.
3) 750 Double Pumper carbs are rated at 20.4" of water Test Pressure when flowed. They are rated at 950 cfm with tested at 28" of water but the carb still flows 750 cfm at the Holley Test Spec of 20.4" of water used for 50 years of carb testing.
Same deal for the 850 cfm carb vs the higher rating 1000 cfm rating. Just the test pressure point changed, the carb still flows 850 cfm at the Holley spec used for 50 years. It is all a Marketing trick to get a buyer thinging he has a larger flowing carb when he takes off his 850 cfm carb and installs the 950 cfm carb which actually flows less cfm.
More Tomorrow.
Tom V.
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"Engineers do stuff for reasons" Tom Vaught
Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward.
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