Holley 1000hp: Annular or dog-leg boosters?
 

Since I'm building a 555 with high lift solid roller cam, AL heads, 10.5:1 compression, etc. which boosters should I get? My engine builder says the annulars help with low end performance but rob power and therefore, get the dog-legs.

I read in the archives that annulars are better for street manners and performance but that was on a small block where low-end torque is always needed. I shouldn't have that problem. :thumbs:

Your opinions are welcome! :cheers:

Hot rod mags....
 

I was reading a recent comparison on the stock, dog leg and annular boosters and they say stock for performance isn't good. Dog leg is better but the annular allows you engine to respond better at lower rpms. I'm not sure if the mag was hot rod but check back a few months on that and Chevy HIPO and car craft. I'm moving this week so everything is packed.

I’m running the Holley 1000HP on my 496, 10.5 to 1, with a Lunati solid roller 260, .701 lift. I went with annular boosters so I can speak only of them, I am very surprised of the response this motor has off idle. It is amazing; just snap the throttle and its there. MotorHead has run them both on the same motor and the same carb so he should be able to give you a better idea of the difference. I think he wrote a response on innovates web site about the difference between them. I think he is running a SB 406.


Neal

For a 555 get dog legs, you will need all the flow that 1000 can produce.

Annular boosters improve throttle response, heck it improves everything, you might loose a couple of HP on the top end, I don't care though because the annular boosters are a step up for a street driven car :thumbs:

Just a note here, some people will go to the next size up carb ( Holley 750 to 850 for example ) if they are going to buy an annular booster carb :D

True, but we are talking about a 555, not a 406. Annulars reduce flow by as much as 40 cfm. They will cost more than a little on the top end.

Get a 1050 HP and your all set :lol:

FYI from CarCraft

http://www.carcraft.com/techarticles...own/index.html

That is the article that I read that made me change to annular boosters, the annular booster carb made more power throughout the RPM both HP and TQ. When I installed the annular booster I got the same results as the article. Here are a couple of lines that really got my attention:

"An annular discharge booster’s multiple holes offer many points for the fuel to enter the venturi as opposed to a single discharge point. At lower air speeds, this offers measurable advantages, especially when combined with the annular’s better signal strength. This is important for situations where large-volume carburetors are used in conjunction with a long-duration camshaft. With a weak manifold-vacuum signal at idle, annular-discharge boosters can greatly improve throttle response and driveability."

And especially these lines :

"If you look at the power differences in the 1,800-2,400-rpm test points, it’s clear how well the annular boosters work. The annular discharge carb was worth a staggering 94 lb-ft of torque at 1,800 rpm"

The test from that article is comparring carbs on an LS-1 with a carb. I would expext the annular to make more power and tq on a mild small block. The same will not be true with a stout 540.

I think annulars are great in street carbs....as long as the motor is not a big inch big block. I ran annulars on my 620 hp+ solid roller 454 with a Holley 1000 anuular carb.

:iagree: John has it exactly right. A 555 at cruise will have planty of carb signal. Down leg boosters on a 4150 style HP for these big engines.

That is unless you're building a tow truck engine thats all done by 5000 rpm....

Mark

I run annular boosters on my 1000 cfm Holley carb and it works great for me.. It's possible that it works great for me because 1000 cfm is more flow than I need so I still get enough air even with the reduced flow due to the annular boosters. Therefore, if you go with a larger carb with annular boosters, you should get the advantages of the annular boosters (response) and enough air flow at the top end..

My part number is 80514..
Looks like ALL new Dominator carbs (at least those offered at Summit) have annular boosters.. Dominators are considered the ultimate Holley performance carbs and therefore it looks to me as annular boosters are the way to go for a performance application.

Click on each carb part number for detailed specs and you'll notice that ALL OF THEM have annular boosters!!!!

http://store.summitracing.com/egnsea...115+4294902722

Does anyone have any other explanation why all Dominators have annular boosters??

A Holley 1000HP seems kind of small for a 555. I think a Dominator would be more suitable for an engine of that size. How did you arrive at the 1000HP decision?

Brett

Annular vs. downleg boosters
 

I am building the LS-4 454 in my 74 coupe. It will have about 9 to 1 CR, CC XE270HR, GMPP 110cc aluminum oval ports, Hooker Super Competitons, and GM casting #569 factory LS-6 manifold. I called Demon for a carb recommendation, with the 850 Speed Demon vac. sec./annular in mind. The guy told me that carb would work but actually suggested the 750 with downleg boosters. He said it is rated very conservatively and can actually flow 930 cfm, so I bought it.

Which one do you guys think would have been better for me. Car is a daily driver with 3.08/auto. Thanks.

Marks69BB,

On an engine this large, going with a standard square flange (4150 bolt pattern) a Downleg booster carburetor is going to give you better overall performance. The annular boosters can actually draw too much fuel at your part throttle cruise and hurt your performance and fuel economy. (On this specific combination)


Yellow-fever,

With the mild 454 and only a 3.08 gear a 750 is going to give you much better throttle response, and drivability.


Technical Support,

Barry Grant, Inc.

www.barrygrant.com

Doug - The engine was a 8.5-1 509 with iron GM R-ports and a very mild hyd cam. It was running a Speed Demon 850 on it which performed flawlessly. Is there any way the 850 could be 'massaged' by you guys to get more CFMs without replacing it entirely? :bigears

I know you are competitors but do you know how your cfm ratings compare with the holleys?

I want to stick with the airbox in the 69's L88 hood since this car is kind of an L88 clone in appearance. No one makes a dominator intake that will fit up under there. Then there is the air cleaner base and screen which are also made for the 4150 style holley. :rolleyes:

The 850 Speed Demon you have is actually the same physical size as the 1000 HP Holley you're comparing it to.

1.562" Venturi
1.750" Butterflies

We run that same carburetor on the GMPP 572" Crate engines without any trouble. As long as the cam specs you're using are going to work with the carburetor you have, you're most likely not going to see any difference going to a 1000.

Technical Support,

Barry Grant, Inc.

www.barrygrant.com

Doug - The 572 crate you refer to most likely has a mild hyd roller for the street.


The new cam will be a solid roller with 262 @ .050, .715 lift. In a 555 I would think, unless the Demon can actually flow over 1000 cfm, it won't be enough. As I asked before, can it be modified to flow more?

And if not, what would be your recommendation from the Demon line? Price?

http://www.4secondsflat.com/Carb_CFM_Calculator.html

I plugged in 555 ci 90% VE and 6700 rpm and came up with 968 cfm carb required.

Now we all know that required is a low end figure. Just like most hot rodded 350's only need 600 some cfm, but run quite well with 25% bigger 750 carbs.

I don't know how high of rpm you're planning, but 25% bigger than 968 puts you right into the 1100 - 1200 cfm range.

Do you also have big CFM heads