how complicated is it to switch from downleg boosters to annular discharge boosters for better fuel atomization and will it be worth the effort for extra power from a street/strip(much more strip)car? it seems like a good move considering the use of a long duration cam,850 double pumper and super victor intake.what do you guys think? annular discharge or downleg? thanks.

Annular boosters are mainley for circle track, for drag racing the downleg boosters are the ticket.

Some try to use the annular as a crutch for an overcarburated situation. They actually make the carb flow less.

To answer your question though, it takes a special tool to R&R the boosters. It's available through Bo Laws, but you might be better off taking it to a carb shop, or sending it to John Kyle at APD.

My understanding changing boosters is not a do it yourself job. Not many carb shops can do it. I've been running an 830 annular booster carb for a couple years. In my case, it has worked well. However, I've had to run much larger jets than you'd expect (79/87). The reason is the carb tends to lean out at higher rpm, about 6200 rpm. By richening I've got the leaning up to 6700 rpm. When I first put this carb on, replacing a 700DP, the car slowed down. Eventually I got the speed back up. I recently borrowed a 750DP with down leg booster. While the results are not conclusive, I think the car will run quicker (the air was better than excellent on the test nights while most runs with the 830 have been in warm to hot weather). I'm seriously considering a Proform body. That way I can do some serious testing. Most people use down legs for a reason. If the annulars were better most would be using them.

Originally posted by Pat Kelley:
[QB]I've been running an 830 annular booster carb for a couple years. In my case, it has worked well. However, I've had to run much larger jets than you'd expect (79/87). The reason is the carb tends to lean out at higher rpm, about 6200 rpm. By richening I've got the leaning up to 6700 rpm. When I first put this carb on, replacing a 700DP, the car slowed down. Eventually I got the speed back up. I recently borrowed a 750DP with down leg booster. While the results are not conclusive, I think the car will run quicker (the air was better than excellent on the test nights while most runs with the 830 have been in warm to hot weather). [QB]I hear an echo.

I have attempted to dial in two 830's and one 750 on other peoples cars.
While they 60ft excellent they tend to lean out at the high end.I suspect the large size of the annular booster is prohibiting airflow at high speeds.
When I finally get the high end good the 60ft gets slower and after a while the plugs foul.
Every time they swapped to a carb with downleg boosters the problems goe away.Granted their 60's are a touch slower.The overall time is quicker.

I think that altering the high speed air bleeds might remedy the problem or at least alleviate some of the high speed lean out.But if one want's to play around with those you probably should have gotten a HP Holley with the removable bleeds as with the standard Holley stuff you need to drill them to change the size.

Doesn't the annular booster spread the gas around a groove with little holes in it so it atomizes better but it does tend to choke the overall fuel delivery down some whereas the dogleg booster just dumps it in out of one big hole so it gets more gas easier, but the atomization quality isn't as good??

pdq67

PDQ, that's pretty much correct but if the engine is a "high velosity" design, the strong signal will allow you to run a larger carb or a downleg style booster without noticing any loss of low rpm responsiveness and idle quality.

On my 468 oval port 10.5:1 1-3/4" exhaust BBC, I did not have any difference in idle or responsiveness while testing (new)carbs ranging from a 750 with a proform mainbody up to a 1000HP with Annular and then downleg style boosters.

Now, if you try to run an 850 with downleg style boosters on a 350 sbc with large port heads and big exhaust, you are asking for trouble.

My recomendation would be to go to a 650 or 750 with a proform main or a 750HP

thanks for the input, guys.i think i'll just wait and see how she acts before deciding to make a move on the boosters.

From what I understand you can modify any holley carb to use screw in air bleeds. Holley sales a kit. you basically drill them out then drill the hole to the correct size then tap it.

Todd