[Chevelle-list] More on Carburetors

[Brad Waller]

Sorry to bring this up late, but I just got to my March 2004 Chevy High 
Performance.  They took a 4400HP/TQ 383 and tested it with different 
sized carburetors.  They used Holley 4150 HP mechanical secondary 
carburetors in the following sizes: 390-, 600-, 750-, 830-, 950-, and 
1,000-CFM airflow ratings.

Amazingly, the 390 did OK.  The 600 did much better (obviously) 
averaging 20 lb-ft more torque and 17 HP.  The 650 bettered the 600 by 
3  lb-ft and 3 HP on average with a few places up by maybe 8 HP. The 
750-CFM model was basically the same, within 1 HP and TQ on average, 
with a few HP or TQ numbers higher than the 650 and according to them, 
no low speed issues.  By the time they go to the 830, they had noticed 
differences down low, but they liked the idle and said throttle 
response was acceptable, and the peak numbers were up a few HP more.  
As expected, the 950 and 1,000 were not as good low down and seemed 
like it would not be acceptable on the street.

I was pretty amazed that the larger carbs did well and the small one 
was not as limiting as I would have thought.  This sure seems to toss 
the theory and formula on it's ear.  I'd say buy a 650 for a small 
engine and a 750 for a larger engine, and only go bigger for high RPM 
and race motors.

Brad Waller