I have been slowly putting my car back to street and I am thinking about switching from down-leg to annular boosters for better throttle response.The carb I have right now is a 1050 body 4150 custom built unit I think from Pro-Max It has Quick Fuel parts and has Pro-Max stickers on the bowls. It runs pretty well the way it is right now but I will be pulling some gear out of it with a transmission change and I am anticipating some tuning issues with the change.
Thanks
Gus

Gus, Drop them in the primaries and give it a try, use a wide band on it to get your tune and you might decide if you like the performance. Tim

All the racers and people I know that ran a annular booster 4150 carb, had problems controlling the AFR above 5000 RPM, they all went fat The other bad thing about annular boosters is they take up airspace in the carb. so they limit the total amount of air that the carb will flow at WOT As much as 80 CFM is what I've been told I have three Holley 1050 Dominators with the same list # 9375 non H.P., one has been converted to annular boosters, it has jets in it that are 20 sizes smaller, # 72 versus # 92 in the other two and it makes 25 HP less with the same AFR on the same engine on the DTS engine dyno the same day 20 mintes apart with no other changes It does drive nice on the street, I had to limit the idle fuel feed and the intermediate fuel feed to get it decent(lean enough) enough to not foul the spark plugs at light part throttle cruise bewteen 2000 and 2500 RPM the other two are rich at part throttle cruise also

I hate to show my ignorance here, but what do they look like, how do you tell them apart? What do the 4781 carbs come with, that will tell me what I have so I can tell them apart.

I read all these posts and have no clue what is being said. Just trying to understand better. Sorry, not trying hijack the thread.

Note the holes in the annular booster. The fuel is admitted to the airstream evenly around the inside of the booster instead of just one or two entry points.