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Fuel System

Carb flow test

Moparts Member
Posts: 2791
From: so burlington,vt usa
Registered: Aug 2000
posted 07-06-2002 09:35 PM

first, let me say right up front that this is by no means the definitive carb flow comparison test.
i dont have a flow bench with enough capacity to flow test a carb, all barrels simultaneously, at the industry standard pressure drop.
IMO, thats the only way to really compare carbs. in any case...this is a set of results from several different carbs, all tested by the same operator, on the same bench.
the test procedure is done flowing one barrel at a time at a pressure of 10" h2o. you add up the results from all the barrels, convert that number to 1.5"Hg(20.4" h20), and thats the "dry flow".
when the motor is running, fuel will be introduced into the flow path. since the fuel displaces some of the area in the venturi, the flow will be reduced. how much of a reduction of flow depends on how much fuel is being introduced. what this means is that jetting influences the "wet flow" capacity of the carb.
an A/F ratio at WOT in the mid-high 12's will result in a loss of flow of about 8%.
this is what i use to determine "calcuated wet flow", 92% of the dry flow.

perhaps if this generates enough interest Carl can add it to the tech archives, and i can add to it as i get more carbs to test.

Holley carbs:
934.0/859.2--4781-2/850DP--no choke tower

modified Holley Carbs:
984.4/905.6--CFS 905, ported 850DP annular
976.5/898.4--BG 9380S3 annular
912.2/839.2--Proform body w/HP baseplate
931.3/856.7--PRH 950HP, Braswell boosters, blended and polished venturi, BG baseplate

BG Claw/Demon carbs:
1000.7/920.6-BG Gold Claw "1025" downleg
964.1/886.9--BG Gold Claw "825" downleg
980.5/902.0--BG Gold Claw "750" annular
980.4/901.9--BG Silver Claw "1000" downleg
947.7/871.8--Speed Demon 850DP

Carter/Edelbrock carbs:
647.4/595.5--69 383 AVS-stock
617.9/568.4--Comp series 625 AFB
767.1/705.3--Comp series 750 AFB
756.2/695.7--Ebrock 1407 750
647.6/595.8--Ebrock 1406 600

All info provided by member fast68ply.


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