Autolite 4300 spreadbore questions

[drdano]

Sorry for the "GM carb" question, but I know some of you probably have a 429 or Cleveland powered car with one.  Are the 4 mounting holes for the carb to mount to the intake manifold in the same location as a standard rochester quadrajet?  i.e, would a 351C spreadbore intake accept a rochester quadrajet?

[chris401]

Sorry for the "GM carb" question, but I know some of you probably have a 429 or Cleveland powered car with one.  Are the 4 mounting holes for the carb to mount to the intake manifold in the same location as a standard rochester quadrajet?  i.e, would a 351C spreadbore intake accept a rochester quadrajet?

When I ran a Motorcraft 4300 on the square flange an open Quadrajet adapter worked. Seemed one end of the carburetor used the same holes as the intake.

[drdano]

This is the adapter I use to go from Quadra jet to regular square bore.  So what you are saying suggests the motor craft / auto lite carb doesn’t have the same bolt pattern.  I wasn’t sure if they were the same or not.

[drdano]

Searched more, I think I found it.  Not sure on the bolt pattern, but the venturi pattern is definitely different. 

[chris401]

I forgot about the primaries being different. That maybe why I used a open/single plane adapter. From here it looks like the 4300 and Holley share all the bolt holes. Here is the Mr. Gasket adapter I used on the 4300 and Quadrajets back then.

[drdano]

Ok, bolt patterns between the Autolite 4300D and the Rochester quadrajet must be the same as that is the adapter used for regular quadrajets.  I initially used the same one on my quadrajet to performer RPM intake prior to making my own custom two-hole unit above out of a four hole version.  Thanks for the input!

[shady]

The quadra-jet has way bigger secondaries and smaller primaries then the ford spead-bore, so no it wont fit a clev. spread-bore intake.
I use the above adapter and you can use it on any intake with the regular Holley or 4100 pattern. One word of caution, when using the open adapter, make sure the base plate screws on the Quadra-jet are locktited in place. If one of the screws comes loose it will be immediately ingested into the motor.  Don't ask me how I know this. I use a thin stainless gasket under the quad just in case.