Thread: Mill Choke Horn or Get New Proform Body
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Old 02-20-2005, 05:00 AM
Cobra 29 Cobra 29 is offline
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Join Date: Jan 2002
Location: Lakeland, FL
Cobra Make, Engine: ERA 427SC FMS 351W
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Default Mill Choke Horn or Get New Proform Body
I have a 650 CFM Holley (4777-3) that runs great with my FMS 351W crate engine but I need to remove the choke horn to provide better air flow into the carb. I can only run a 2" high air cleaner with a slight drop base (Ford Racing 13").

Should I take the carb body to a machine shop to have the choke horn milled off or purchase the Proform replacement carb body (67100C). My base plate bore is 1 11/16 which will fit the new Proform main body. The primary venturi diameter will increase by 2/16" and the secondary venturi diameter will increase by 1/16".

I really like the responsiveness of the 650 as it is now and fear that the venturi diameter increase will reduce the responsiveness. Most of my driving is between 2000 and 4500 RPMs.

Has anyone made this swap? What was the effect on mid RPM responsiveness? Milling the choke horn away would increase the air flow but the modification can not be reversed.. Thoughts on what direction to take?
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