I have some questions that I'm having some difficulty finding on the Internet how do the major carb companies modify the flow characteristics of a holley carb?
Hypo thinking if I had 390hp 4 barrel that I'd like to flow around 700cfm how would I go about doing it this is just a what if scenario
Thanks in advance

 

In that scenario I would sell the carb and buy a larger one.
390's are very popular in stock car circles as well as small cid builds. Last time I looked they held a pretty good value.

Beyond that choke horn, venturing enlargement and reshape, baseplate, thinned throttle shafts and screws

 

could base plates be swapped as well

 

Depends on the carb family
390 unique
600 unique
650-800 share baseplate patterns
850 unique

 

Well the 390 is going to Eric at HI for some booster upgrades and his E85 blocks after the holidays.

But is it possible to tapper cut the under side of the main body to accept alarger baseplate? Would it kill the booster signal, or act weird with a 390hp main body and 750 baseplate?

 

The carb in stock form flows 390cfm with a 1.5"hg pressure drop. How much will the exact same carb flow if you shove 15psi at it? This is why total airflow isn't much of an issue with boost & carbs. More boost means more air molecules can fit down the same size hole.

 

A more effective method is to make a spacer that installs between the base plate and the main body. You would need to create tapered openings in the spacer to transition from the main body to the base plate. BLP offers a spacer like this for installing an 850 base plate (1.750" throttle blade) on a 650 - 800 main body (1.6875" throttle blade). Installing a base plate with larger throttle blades will typically contribute to increased signal in the venturi due to an increased pressure drop that is created at the transition from the venturi to the throttle blade openings. The larger throttle blades will also obviously contribute to increased air flow through the carburetor.

 

And Holley has done the mix-n-match on production carbs, too. A 650 is a 600 mainbody with a chamfer in the base of the venturis to match up to a bigger 750 baseplate, and an 830 is a 750 baseplate with a chamfer in the top of the throttle bores to match up to a bigger 850 mainbody.

 

Thanks guys, catherder you pointed this out too me on a different post about the mix and match of a 650 dp and that's what got me thinking about trying something similar to what holley did with the 600 mainbody on a 390 mainbody but us a tapered bit and open it up to my desired size.
One of the only reason is I just bought a nice boost referenced throttle plate for my 650 and I had the feeling Eric would want to us the 390 and I hate to not us the base plate its a nice unit