[Lerry: The Body Ventura..]

I've heard it said that annular type boosters eat up cfm's? I have a Holley (9380) 850 race carb. Which has the annular type boosters. Will it still flow the 850 cfm's with these large boosters blocking air flow compared to the 850 dogleg style?

[Lerry: The Body Ventura..]

I've heard it said that annular type boosters eat up cfm's? I have a Holley (9380) 850 race carb. Which has the annular type boosters. Will it still flow the 850 cfm's with these large boosters blocking air flow compared to the 850 dogleg style?

[GREATGTO]

you have a lot more things to worry about than losing a couple cfm here or there, youre carb will work fine, as far as it losing cfm one can only say with any accuracy if they actually flowed one, best off posing this question to a carb builder who knows the truth from bench experience. What size engine do you have?If its not a race engine with ported heads chances are it doesnt even need 850 cfm, but like I said, im sure it will work fine, iv run an 830 holley on a 400 for several years, it has annular boosters too, its one of the best carbs out of the box that iv ever had. good luck

[esahlin]

I saw a dyno test done in a Car Craft issue that used two 850 Demon carbs...one with the Annular boosters and the other with the downleg types....the annular booster carb made 1 % more horsepower at the peak.....5HP on a 500 HP chevy 350. Not sure if that 5HP was statistically significant given the many variables in dyno testing...but I think it shows you wont be losing anything with annular boosters....the annulars are also supposed to increase lower rpm throttle response because of the enhanced atomization they provide.

[torqjunki]

We have done some back to back testing with a 462 with d-ports that flow well through low and mid lift range. We tried an 850 against a 950HP. The 850 was 2 tenths and 2 mph quicker in the 1/8th mile. THe venturies in the 950 are the same as a 750 with a baseplate like a 850 and has annular boosters. How they get 950??? I don't know, but I think the annular booster is great for an engine that looses signal to the carb on the shift. THe high velocity of the d-ports need more cfm and will recover nicely on the shift without annular boosters.

[Skip Fix]

Dave, In talking to Tom V and also Demon on some of their products they use a higher test pressure to come up with teh HP cfm vs the old DP ratings. Kind of like comparing head flow numbers at 28 vs 25. Not the same,apples and oranges.

Look at the BG site and they have venturi and throttle sizes on al carbs, . Some flow more with th same sizes for the same reasons. I believe their carb drops from an 850 to a 825 with the larger annulars.

[tempest455]

It will also idle much better w/ the annular.

[GREATGTO]

im not a big fan of out of the box performance, but i must say i love my 830 holley annular boosters, best out of box carb in my book, people tell me the 850 is also good

[Steve C.]

I bought a 'worked' HP950 with annular boosters from PRC in Houston and we were disappointed with the performance. I sent it back to them and had the annular boosters removed, after doing so the car really responded to the change. I wish I could respond with the numbers here but this was quite some time ago and I don't remember the ET difference or 60-ft.
I just suspect that the cfm difference was major reason.

[esahlin]

Steve-

Thats interesting information.....I always hear/read about alot of "praise" for annular boosters so I always ask that if the annular boosters provide more performance/throttle response in a majority of the engine/car combinations then why doesnt Holley or Demon just install them in all or the majority of the "HP" type carbs from the factory? The majority of those carbs come with the "down leg" HP type. Granted, it will depend upon application and the annulars will be beneficial in some applications but there must be some drawbacks compared to the down leg HP type.....as Steve might have experienced in his testing. You can buy the annular boosters for about $35 (for 4) new and install them whereas the HP type downlegs are $15 (for 4).

Skip....thats what I read....its all marketing now days....advertise that its a 950 and everyone will think its better than an 850...and most of the time its hard to find out what the nitty gritty details are....I think its great that Demon puts those hard to find details on their website.

[Taff]

The annular booster design also works well in blowthrough boosted applications,allows more fuel to be pulled through apparently. I don't suppose the small CFM loss would be of any concern in that application.

[Steve C.]

I got the annular booster set-up because of the throttle response/heavy car stuff I had read about. Unfortunatly I cannnot remember the 60-ft's involved then. The top end due to the small cfm loss may have been hampered (?). But when we switched I don't remember how the 60-ft was effected, and so I just might presume the top end picked up with the change. Thus a better ET.

[Lerry: The Body Ventura..]

Why I asked is I think I'm pretty much border line with an 850 as it is. If these annulars are taking away any, I'm very seriously thinking of moving up to the Dominator 1050. OMT is getting away with it on his 400 with a very similiar motor design. Plus I already have a Warrior for a Dominator..

[Skip Fix]

Before I decided which Demon I talked to BG tech. Got 2 different guys one said annulars better for heavy cars, other said downlegs better! I wnet with the downlegs.

When Ford used a Holley on their 351 trucks and Broncos(I had one) They had annular primaries and plain secondaries.

The HP downlegs I think do have a "step" in them to increase some atomization or draw if my memory is correct. 1000HP has the same dimensions as an 850 DP!

The Demons with replaceable boosters can swap them that have differrent feed holes form the fuel bowls.

[Lerry: The Body Ventura..]

Correct me if I'm wrong but it seems heavier cars can be compensated with the various cams and squirters availble for Holley? How I take it with the annulars is more of a vacuum issue. When running larger cam profiles, vacuum is weak and the annulars are alot more sensitive to the fact?

[Herb Hagan]

That's exactly correct Lerry, the annular boosters improve the carb signal/atomization under low vacuum conditions... ie big duration cam @ idle. Have a 750DP w/annular boosters and can get perfect idle characteristics with only 4-5" vacuum @ idle. I can get the engine to idle below 500 RPM, other carbs would not idle below 1000 RPM's. Fully responsive to all 4 corner idle mixture adjustments as well.

Herb

[455T/A]

I like my boosters

[74t/a]

Using annular boosters has little or nothing to do with vehicle weight. It has to do with the type of cylinder heads, intake, cam etc. and other parameters. You can only find out on the dyno or track if the annulars work better.

Usually, pontiacs respond to annular boosters, but not always. Also, out of the box carburetors run very rich on the idle circuits.....which also effects part throttle mixture. You have to lean it out a bit to make it run well. I also like to balance out the front to rear circuits to make them more even. The rear is more rich than the front in factory calibration.

One more thing....Demon carbs are not all they are thought to be. I have made more than 50hp more with a Holley carb than a Demon on a 750hp engine. Demon metering blocks are very hard to "tune" the power back. If you substitute the holley blocks on there you can get some of the power back.

[Skip Fix]

I would think the track would really be the best test as the acceleration is the key not just Hp/torque numbers that could be similar on the dyno. I can only assume they said annular for a heavy car for better atomization to be more responsive on the heavy weight car.

It suprising how long the idle circuit stays on. After getting a wide band O2 sensor and putting around my son's 81 that right now has a 3310 on it you could see. When the idle was adjusted fat at 10.5:1(best vacuum!) cruising at 1500 was too fat in the 11.5-12 range. Leaned out the idle and part throttle cruise got 12.5-13.

[455-4+1]

Sorry to ghet off the topic a little but a very important note on Demon carbs with annular boosters

Be certain to check the annular boosters on your Demon carb prior to the first time you use it.

My car ran like crap at the end of the first run when we switched to an 850cfm mighty demon with annular boosters

Pulled over at the end and checked the carb and found the top section of one of the rear boosters lodged between the main venturi and the booster ring !!!!!!

The thing could be pulled in and out by hand

Would hate to think what would happen if it was ingested (probably not a gain in power!!!!)