Originally Posted by carbking
Buckshot - with all due respect, there is an error in the content of your above post.

While throttle bore diameter has meaning, the airflow is determined NOT by the throttle bore diameter, rather the internal venturi diameter. This error is very wide-spread.

For better understanding, even though this article is a Stromberg single barrel updraft, I think it will add understanding:

Example of different air flow, same throttle bore

If the imitation were a genuine Carter of the same size, the air flow on the primary side would be 250 CFM.

Most Q-Jets prior to 1976 have a primary size of 150 CFM.

I'm too lazy to figure the relative air velocity difference, but it is SIGNIFICANT!

Waveski - you may find an unintended result of higher vacuum!

Thank you Jon for your expertise and vast knowledge on this subject. I don't pretend to know all of the design and technical aspects of carburetion, my experience is mostly hands-on and some research/reading for rebuilds and fine adjustments. Waveski asked about the difference between the Edelbrock 1405 and the QuadraJet, the numbers that I posted were what I found on the web, venturi diameter was not listed. Thank you for the details and clarifying the possible results.
Jon

Last edited by 78buckshot; 02/19/2025 11:44 AM.
1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy