I saw a post where Holley was getting off of their 660 cfm #4224 carbs.
Many years ago that was a popular carb for the Small Block Chevy Racers when used with a Tunnel Ram. The carbs could be modified by a Drag Racer like Paul Bevins (RIP) to where they worked pretty well on the old mid 10 second drag cars in the 1972-1973 time frame on the strip.
Here is a link to a Super Chevy article from the 1973 days.
http://forums.superchevy.com/chevy-h...-paul-blevins/
John Dianna wrote the article. Excuse the title where they call the carbs #4334 Holley carbs vs the correct number #4224 carbs.
They get the later text right though. Someone did not proof read the article apparently.
So the article is about Paul's Corvette 327 cid Race Car with the Tunnel Ram and the Holley carbs along with the mods he does.
1) Paul modifies the Cam and Slot actuated linkage by increasing the delay of the secondary openings so that the engine is basically launching on one "carb" (composed of the Primary barrels on the first carb and the Primary barrels on the second carb).
Basically he is delaying the Secondary Blade Openings until the Primaries are half open vs just off idle in a stock Holley #4224 built configuration.
Then the "delayed linkage" opens up the rear barrels on the two carbs.
So the carbs are basically changed from a "Idle Position/ WOT Carb Position" to a lower horsepower "Combined Carb" situation to a combined dual quad WOT situation.
Paul also delays the Pump shots on the center squirter carbs until much later and also modifies the cam position on the cam levers.
Paul restricts the Idle Feed Restrictions using fine wire.
He keeps the 4 shooter nozzles the same as stock (.025") per nozzle.
(ALL OF THE MODS ARE EXPLAINED IN THE ARTICLE)
A lot of OLD SCHOOL Holley Carb Tuning as in those days you did not have access to the Metering Blocks out there today and the ability of change orifices easily.
Plus the carb knowledge is much higher today.
So the people who will buy the carbs will get some new Holley 660 cfm carbs but the reality is the #4779 750 cfm double pumpers are a lot better Tunnel Ram or M/T Cross Ram Dual Quad carbs with the right modifications.
Tom V.