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grumpy_old_fart · 05-12-2013, 04:32 AM

Generally, (and i mean generally in naturally aspirated situations) a 4150 carb will start using the main jets and bleeds about 1500 rpm, or right about the time your throttle blade clears the idle circuit.

an easy way to test the theory is to get the truck to idle... then, unhook turbo piping, adjust the carb to where the idle circuit is no longer in use... you would have to remove the carb, screw the idle screw in until the throttle blade is above the transfer slot, put it back on and attempt to start it to get an RPM reading. probably not the most fun.

once you get the rpm reading, you have a baseline.

05-12-2013, 04:32 AM	#6
grumpy_old_fart Registered User Join Date: Apr 2008 Location: Oakland OR Posts: 2	Re: Tuning a Holley 4150...? Generally, (and i mean generally in naturally aspirated situations) a 4150 carb will start using the main jets and bleeds about 1500 rpm, or right about the time your throttle blade clears the idle circuit. an easy way to test the theory is to get the truck to idle... then, unhook turbo piping, adjust the carb to where the idle circuit is no longer in use... you would have to remove the carb, screw the idle screw in until the throttle blade is above the transfer slot, put it back on and attempt to start it to get an RPM reading. probably not the most fun. once you get the rpm reading, you have a baseline. Last edited by grumpy_old_fart; 05-12-2013 at 04:33 AM. Reason: clarity.