[i82much]

Been reading a lot of great reviews on annular carbs for street use. Thinking it might be fun to find a good holley core and try a booster swap. The too is expensive but not too worried about that.

Bigger concern is how much recalibration is involved? Would i need to recalibrate all the circuits or just main jets and maybe high speed air bleeds?

[steve25]

You must be concerned that your carb is too big to give adequate low speed torque because that it the main reason for doing this .

It’s also been found that in terms of maximum power that the fuel used along with the air temp that the use of these type of boosters can be a double edge sward .

In some racing situations the greater atomized mass of fuel ( fuel cloud / plume) was cutting into the level of air the motor could bring in which was cutting into the peak power being made on NASCAR track motors.

Basically if your carb is not too big then with these types of boosters the hotter the incoming air charge the less you need the fine atomization these boosters produce.

[Steve C.]

https://forums.maxperformanceinc.com...nnular+booster



.

[i82much]

Originally Posted by steve25

You must be concerned that your carb is too big to give adequate low speed torque because that it the main reason for doing this .

Nah ... it's a quick fuel bd-850, more or less a jazzed-up 4781 on a 505, OF 1.0 cam, rpm intake, 87 cc old style e heads. With a 3.54 gear and an ultra wide muncie, it runs great.

I ask because I am bored and like to dork around with stuff ... just thought it would be fun to find a core on craigslist, convert it to annular, and see how it compares.

[Half-Inch Stud]

Vizard goes to show that chilled fuel should bring a decent hp boost but does close to nothing until ya finish the thought; use the annular booster for proper cold-fuel atomization.

Then the (cold) fuel will re-attain the 25% vapor needed to perform peak combustion.
The air inhale also got cooled for a denser vol-metric fill.
Seems to me the annular boosters work superior with ambient tank temp fuels. The depression signal is stronger than all the other Holley boost rings.

I'd say go for dorking around.

[steve25]

I give you my Thumbs up for going for it by all means!

If you could have another person drive your car as it is now and then after the swap to compare , but also make notes each time as to that days air temp , Hg pressure and Humidity so your results will be apples to apples.

[i82much]

Motivation here is that I don't see availability of annular main bodies with a choke ... I like my choke!!!

[PAUL K]

Annular boosters can help a lot if the combination is set up to take advantage of them and they are properly selected and tuned.

I think they're expectations are kinda comparable to Rhoads lifters. They work as advertised but if the combination isn't set up to take advantage of them they won't make much difference.

[i82much]

Originally Posted by PAUL K

Annular boosters can help a lot if the combination is set up to take advantage of them and they are properly selected and tuned.

I think they're expectations are kinda comparable to Rhoads lifters. They work as advertised but if the combination isn't set up to take advantage of them they won't make much difference.

it's either eff around with carburetors or get drunk and text ex-girlfriends for this guy. I think we all know I need to buy that booster tool NOW.

[Brentco]

I’m generally a fan of annular boosters — it’s too bad they’re not offered on more carbs. So a booster swap sounds like a cool project.

Based on the factory spec sheets I’ve seen, the difference with the annular booster versions seems to usually be confined to the jetting (a bit smaller prim and sec). But that’s just how they set them up from the factory — it isn’t necessarily the optimal tune versus downleg versions.

My WAG would be that the chief difference would be the main jets, but if you’re really persnickety about the tune you could end up with small tweaks to other circuits as well.

But if you’re hunting for something to dork around with, all the better!

[Tom Vaught]

I have changed a lot of carbs over to the Annular Booster over the years.
Low speed drive-ability is improved for sure.

I have had my booster tool for 50 years. Not going to wear it out in your lifetime.

People over the years have even added more holes to the booster insert to improve signal with the larger 850 carbs.

The Annular Booster is a drive-ability "fix" for the larger cfm carbs 4 BBL or 2 BBL.

I have converted quite a few of the #4782 & #4783 2-BBL carbs over to the Annular Booster. These are mechanical secondary 6 pack race carbs.

Tom V.


R4782 2300 355 37-1537 37-933 6-504 122-64 N/R N/S N/R 125-65 0.031 N/R 108-83-2 108-89-2 N/R N/R N/R N/S N/R N/S 1-3/16 N/R 1-1/2 N/R


R4783 2300 500 37-1537 37-933 6-504 122-82 N/R N/R N/S N/R 0.028 N/R 108-83-2 108-89-2 N/R N/R N/R N/S N/R N/S 1-9/16 N/R 1-3/4 N/R

[i82much]

Originally Posted by Tom Vaught

I have changed a lot of carbs over to the Annular Booster over the years.
Low speed drive-ability is improved for sure.

I have had my booster tool for 50 years. Not going to wear it out in your lifetime.

People over the years have even added more holes to the booster insert to improve signal with the larger 850 carbs.

The Annular Booster is a drive-ability "fix" for the larger cfm carbs 4 BBL or 2 BBL.

I have converted quite a few of the #4782 & #4783 2-BBL carbs over to the Annular Booster. These are mechanical secondary 6 pack race carbs.

Tom V.


R4782 2300 355 37-1537 37-933 6-504 122-64 N/R N/S N/R 125-65 0.031 N/R 108-83-2 108-89-2 N/R N/R N/R N/S N/R N/S 1-3/16 N/R 1-1/2 N/R


R4783 2300 500 37-1537 37-933 6-504 122-82 N/R N/R N/S N/R 0.028 N/R 108-83-2 108-89-2 N/R N/R N/R N/S N/R N/S 1-9/16 N/R 1-3/4 N/R

have you found that you need to recalibrate the carb extensively? or maybe just rejet?

[Dragncar]

Originally Posted by i82much

Been reading a lot of great reviews on annular carbs for street use. Thinking it might be fun to find a good holley core and try a booster swap. The too is expensive but not too worried about that.

Bigger concern is how much recalibration is involved? Would i need to recalibrate all the circuits or just main jets and maybe high speed air bleeds?

Performance Carb and Speed did a 1050 for me and installed some billet 12 hole annular boosters in the build.
I asked them about putting some annular boosters in a HP 850 I have raced for years. And he told me not to do it. He likes the down leg boosters those carbs came with stock.
4500s need annular boosters because that is a big hole to get a signal out of.
They give free tech advise so you can call them up and ask them yourself if you like.

[i82much]

Originally Posted by Dragncar

Performance Carb and Speed did a 1050 for me and installed some billet 12 hole annular boosters in the build.
I asked them about putting some annular boosters in a HP 850 I have raced for years. And he told me not to do it. He likes the down leg boosters those carbs came with stock.
4500s need annular boosters because that is a big hole to get a signal out of.
They give free tech advise so you can call them up and ask them yourself if you like.

great info, thank you!

[Skip Fix]

The old Demons with interchangeable sleeves also had interchangeable boosters.

[TCSGTO]

https://www.ebay.com/itm/28178171448...ce9af8d4a1fd19
These main bodies have a 1.59” Venturi and come with angular boosters. Probably cheaper than getting the tool and boosters or sending it out to have your converted. You could also reverse it if it doesn’t work for you.

[Skip Fix]

My Mopar buddy used that main body and some of my extra parts to make a carb for his 500" Mopar. AFR and driveability was better than any other carb. But he runs a Hilborn Stack EFI now.

[Cliff R]

"I asked them about putting some annular boosters in a HP 850 I have raced for years. And he told me not to do it. He likes the down leg boosters those carbs came with stock."

Dating clear back to the 1970's when I used to wear out the main body threads on trunk loads of Holley carbs I'd test on my 440 powered 1970 Roadrunner I'd agree with that statement.

Tried ALL of them, 3310's, 4777, 4779, 4780, 4781's and a even a few factory Holley carbs like the ones they put on the factory 302's, Mopar 383 Magnum engines, 375hp/396's, etc. Even in my later years I did some dyno, street and track testing with later model Holley carbs with "modern" boosters. Even tested the "undercut" booster designs and boosters with mulitple holes in them supposedly to improve sensitivety without increasing booster area.

I see NOTHING at all at the track with any of that sort of thing.

However, as Tom mentions "low speed driveability" is improved some. So on the street "easing" into the throttle and driving very gently there is a noticable improvement with the larger annular booster designs. At WOT they may impove atomization a bit but they take up more area, so a trade off in efficiency vs CFM on the smaller venturi diameter units.

It's kind of interesting but Holley really did go a great job with many of their older designs. With very few modifications they were excellent right out of the box and even to this day you aren't going to easily outrun one........

[PAUL K]

Different combinations will respond to different size throttle bodies, venturi's, boosters, injectors etc.. There "is a reason" Holley makes a crap ton of different configurations. If one is not finding any differences testing on the dyno or at the track most likely something else is skewing their results. They don't all "run the same".

I recall years ago I built a basic "hot rodded" 750 double pumper for a gentleman with an eleven second Trans Am. The 750 was faster (first pass down the track) than the 800 cfm Q-jet he had been tuning on for years. Then he tried a professionally tuned 850 that was deemed by a popular Pontiac engine building/dyno shop as being "perfect". That carburetor slowed the fellows Trans Am down also.

Another benefit with having several styles of carburetors to choose from is they can be custom tailored to the drivers personal preference (a place where that butt meter is highly effective). Some folks might perfer the notch in the pedal to control the secondaries you get from a double pumper. Another might perfer the crisp light throttle response from a spread bore. Some guys might perfer the jumpiness of a 1 to 1 throttle linkage. These are some of the "reasons" Holley provides us with so many different options.

I guess if they ALL ran the same, everyone would run a well tuned Q-jet.