I run a autolite/motorcraft 2100 2v 300 cfm which has great throttle response but i feel it struggling on higher revs.
This on a stock 289 with higher flow headers and exhausts.

While there is a lot of calculations and formulas about how to calculate the right cfm for your displacement and revs, i've been slapped around mentioning them the last time.
with another bit of thinking i figured that a 4 barrel carb is in the end a 2 barrel carb where secondaries eventually open.
So for me a 600cfm 2 barrell will be way overcarbed as they open in direct relation to my throttle pedal.
a 4 standard barrel will open the first 2 according to throttle and from a specific (about 2 third open) throttle position open the other 2. Then there are those 4 barrels that open the secondaries via vacuum. For this I guess they are opened as the engine needs it and not what I am pressing on throttle. This then should be much more save for overcarbing.

So from all that I guess your best bet is: contact holley. tell them your application and what you want and they'll tell you what you need.

All the above is pure theory that came to me on a toilet seat so don't take it all for granted ... ;-)

Kalli

 

750 Mighty Demon on a way warmer than "stock" 408....

A 289 is 70% of a 408

A 650 is 86% of a 750

70% of a 750 is 525...... HMMM....

 

Biggs 750 on my 410c

 

I'm gonna get the 650 holley avenger for my 289...is that too big?

 

That depends on the 289. 650 is way too big for a stock 289, but a fully built high revving 289 would be ok with 650, depending on the carb it may be better off with something like 550-600, or as high at 700. If you use a special built, highly sensitive carburetor that can meter on virtually non existant vacuum, you can go larger, if it's an old carb that has medicore boosters and needs stronger vacuum to get signal, then you need a smaller carb.

 

the holley avenger comes in 570 and 670, and unless you have one hellofa setup a 670 is too big. this is exactly why i went with a 570. now, if i had a cam with a smaller duration i would be perfectly fine but i need adjustable air bleeds because i have very low vacuum @ idle which means i need a proform. im still on the fence if i want their 600 street series with vacuum secondaries or if i wanna say f*ck it and grab a 650 DP.

i'll probably be better with the 600 though.

 

Barry Grant makes a 575 Demon carb, but I can't recall if it's for the small cams or the larger cams that the metering system is setup for.

 

the air bleeds are not adjustable, which puts me right back into a proform. i am so sick of buying different carbs because i cannot adjust certain things that should be adjustable.

if i had a mild cam, a regular holley would work great - but for anyone with a radical cam i HIGHLY recommend a proform or equiv.

 

750double pumpon my 289.

 

dude.... thats HUGE for that motor unless you have some crazy *** stuff done to it