[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?

[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.

[455T/A]

I like my boosters

[tempest455]

It will also idle much better w/ the annular.

[Skip Fix]

Braeswell has some really good stuff. Even Tom Vaught had good things to say about them. I know the NASCAR guys use him alot.

[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 need to make a correction regarding my situation with the annular boosters. Apparantly my slower ET had little, if anything, to do with the loss of cfm. For which I was told by an outside source might be as much as 20 cfm under some situations and the specific carb involved.
I talked with John today about our situation and he indicated our problem was in the 60-ft. Apparantly with the annular boosters we had a very bad stumble and dispite trying to overcome the situation it helped very little. Something about a very strong signal and not being able to make it lean enough, or something to that effect. Not 100 percent on that statement, but anyway after the change of boosters the 60-ft came back and we picked up 3 tenths.
Like 74t/a suggested the type of heads, intake, cam, etc and other parameters are involved and each combination is effected different. On mine they did not work.

[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.

[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.

[bmpmdf]

455-4+1; That is one reason I take all new carbs apart before even trying to use them. Between loose parts and shavings in every brand, I trust none of them.

[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

[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?

[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.

[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.

[esahlin]

Check out these Braswell patented Nascar boosters on the Braswell site....they dont seem to be much different than the older Holley downleg design....This braswell design supposedly has a shown a proven increase in torque. I dont have a car consistent enough nor dyno opportunities to test them adequately.....but i do have a Holley booster installation tool....so Ive though about giving them a try. Maybe they are only effective in the upper RPM range that Nascar sees.....dont know just interesting stuff. Must be something too them if Braswell went to the trouble to patent them.


http://www.braswell.com/prod_catalog...d_boosters.htm

[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?

[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.

[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.

[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..

[455-4+1]

bmpmdf

Ditto on that one

My carb had a list of problems longer than my arm. Even though it was "wet tested" and signed off (yeah right) it had the following

Float bowls full of swarf

Junk in the primary needle and seat (wouldnt move)

Drilled passages in metering block 1/2 blocked by tail out from intersection drillings

Accelerator pump linkages not adjusted properly (no clearance at bottom of stroke)

One side of secondary shooter not drilled properly (fuel only weeped out) signed off on check sheet (yea right)

I admit I never tried to remove any parts of the booster assembly. Somehow at the time I must have overlooked this as I never gave it a thought. Maybe something in the back of my mind told me things like that shouldnt fall out !!!!

Sorry for highjacking the post a little but I thought it important to bring up since the discussion was about annular boosters.

When you get your new (or used) carb with annular boosters, put your little finger inside the booster (size permitting) and see if you can pull out the top ring.