Big block Quadrajet vs Small block Question

DanMcG · Oct 13, 2019

I picked up a few quadrajet carbs and I thought I rebuild one for my 78 that has no choke. This will be a first for me.
But my question is, one of them is a 17057221 which is listed as for a 76-77 454. On the outside it looks the same as the other small block units, so what all is the difference on the inside?
While I'm at it, is there any value to this BBc carb core?
Thanks.

75gmck25 · Oct 13, 2019

Nearly all Quadrajet 4 barrel carbs are designed to flow up to about 750-800 CFM, but GM had various ways of restricting them so they could be used on different engines (linkage stops, etc.). In general, you can use them on either a small or big block without any issues, but might have do do some fine tuning. I suggest reading through the Cliff Ruggles Quadrajet book to get a better idea of how they were modified.

There are also a few Quadrajets that have less restriction in the venturi area, so they max out at about 850 CFM, but they are quite rare.

Bruce

DanMcG · Oct 13, 2019

Thanks for the info Bruce, I have the book you mentioned, but just haven't read it yet.

Matt69olds · Oct 14, 2019

Things like air bleed, idle down tubes, obviously jets and metering rods all effect calibration. I would suggest calling Cliff with as much information as possible about your particular engine and drivetrain. He will tailor your overhaul kit with the proper parts.

Big block Quadrajet vs Small block Question

DanMcG

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