I'd be interested to know how the "responsiveness" was with the different carbs. I've read that with larger carbs, you loose responsiveness in the low end, which you can't really measure on a dyno.
Tom Tomlinson -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Brad Waller Sent: Monday, March 01, 2004 1:12 PM To: The Chevelle Mailing List Subject: [Chevelle-list] More on Carburetors 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
