Topic: Stock Quadrajet CFM?

[ta78w72]

I searched and searched to try to sort this out and found the answer in "Rochester Carburetors" by Doug Roe.  A table on page 108 gives the desired information.  If the primary venturi is 1-3/32-in you get a CFM of 750.  If it's 1-7/32-in you get a CFM of 800.  Looks like Grand73Am is correct.

By the way, there's a picture of each venturi on page 109.

Doug's book is pretty good and is a great compliment to Cliff Ruggles book.  One of the beefs I have with Cliff's book is it has no index.  Indexes are a PIA to do, but they're invaluable.

[marx3]

That book is great, The picture opretty clearly shows the difference between the venturi size, it's a little hard to tell when you dont have the book at hand though. And for the record, some electronic carburetors from the 80's had a stop on the butterflies, that would limit the max air-flow, it is mentioned in Doug Roe's book too. They could easily be measured at around 650 cfm.
 Btw, it dont matter if you have a 750 or a 800 on a 403. It will never eat that much air anyway unless you really spend some money on it, or rev it to 10k rpm ;-)