sportsuburban
New Member
I just rebuilt a 4578 BBD on one of our 383 Sport Suburbans. Carb was totally disassembled, soaked in Chem-dip, chromated and reassembled. All gaskets and accelerator pump are new. I converted the sealed metering screws to a conventioal full length screw.
Engine runs good with the carb but I cannot find adjustment specs on a few things and hope someone knows.
1) the metering screws in throttle plate - set to 1-1/2 turns. Seems to work?
2) the metering screw in the rear above the vac inlet - set to 1-1/4 turns as I found it but no idea if that is right.
3) and most importantly, the jet/metering screw in the top of the air horn under the welch plug with the spring loaded check valve under it. No idea on the setting on this one as the threads are messed up and I could not check off bottom. Ran it back to about where it was but any help on what it does and settings are appreciated. Can't find these parts on any diagram anywhere.
Going to hook a wideband A/F gauge on today to see what that shows as it smells a bit rich.
Thanks for the help.
Engine runs good with the carb but I cannot find adjustment specs on a few things and hope someone knows.
1) the metering screws in throttle plate - set to 1-1/2 turns. Seems to work?
2) the metering screw in the rear above the vac inlet - set to 1-1/4 turns as I found it but no idea if that is right.
3) and most importantly, the jet/metering screw in the top of the air horn under the welch plug with the spring loaded check valve under it. No idea on the setting on this one as the threads are messed up and I could not check off bottom. Ran it back to about where it was but any help on what it does and settings are appreciated. Can't find these parts on any diagram anywhere.
Going to hook a wideband A/F gauge on today to see what that shows as it smells a bit rich.
Thanks for the help.
