How do I tell the difference between a Square bore and a Spread bore application based off looking at an intake manifold...or if anyone what the Holley 300-64 intake manifold is could you let me know......thanks.

 

Square bore carbs have four equal size throttle bores.Spreadbores have 2 small primaries and 2 larger secondaries..An example of a spread bore is a Q-jet..The intake for a sqare bore has a square flange while the one for a spread bore has the shape that outlines the sides of the throttle bores

Daz

 

http://www.holley.com/HiOctn/ProdLin...SM/300-64.html
Square.

 

I have the performer rpm spreadbore. I noticed that it has 2 sets of mounting holes(8 holes all together) for the carb. Was there more than one style mounting for spreadbores or what is the other set of holes for?

 

Square.

 

so I could mount either? It still has the odd shaped holes for the spread bore? Would the square bore still clear?

 

Yep.

http://www.edelbrock.com/automotive/index.html

Click on Intake Manifolds, Small Block Chevrolet, about 2/3 down is the description of your manifold that tells all.

 

Well for now I am sticking with the quadrajet anyway, but if I were to use a square bore on it would it perform as well as one that was designed specifically for squarebore?