Carburetor ????

[grs]

What is a square bore, and a spread bore carb. What is the diff?

[66Submarine]

Square bore means the primary and secondary circuit is symmetrical. Spread bore means that the primary circuit is smaller than the secondary. For example; a regular 750 Holley is a common square bore carb, and a Rochester Quadrajet is a common spread bore.

The idea with a spread bore carb is that when you are just normally driving with the primary circuit it acts like a smaller carb. The airflow/vacuum signal is stronger/faster, and that (in theory, anyway) makes it more efficient/precise. But unlike a smaller carb, you still have the larger secondary circuit when you stand on it.

[grs]

Well I learned something today. I guess you can learn an old hillbilly new tricks.

[tincan1966]

Originally Posted by 66Submarine

Square bore means the primary and secondary circuit is symmetrical. Spread bore means that the primary circuit is smaller than the secondary. For example; a regular 750 Holley is a common square bore carb, and a Rochester Quadrajet is a common spread bore.

The idea with a spread bore carb is that when you are just normally driving with the primary circuit it acts like a smaller carb. The airflow/vacuum signal is stronger/faster, and that (in theory, anyway) makes it more efficient/precise. But unlike a smaller carb, you still have the larger secondary circuit when you stand on it.

THAT was one of the best explanations, I have ever seen to describe the differences!