1000 cfm race Demon

[6.50camaro]

Just get a used 1000 cfm Race demon carb . Does anyone have the standard calibration data as far as air bleeds {idle and hi speed} , emulsion jets and squirter sizes. on the general competition GC vs. The Drag Race DR version . Dan

[cpmotors]

Maybe this helps

[6.50camaro]

Maybe this helps

Yes that's what I was looking for . I had saw that a few years ago on BG 's website but could not find it now online .Holley does not have that info on their website like Demon did before Holley bought them out. Thanks so much , Dan

[1980RS]

Did you know the Race Demon's have replaceable thread in booster if you can find the tool and boosters to change them out. I am surprised more carburetor companies do do that.

[6.50camaro]

Yes I did know that . that easiest way to tell the difference between a Race demon and a Mighty demon. Dan

[6.50camaro]

So I took the bowls off to check the metering blocks . And I found all 5 holes had E-jets in them none plugged as on the spec sheet posted . I have to get a set of pin gauges to check the sizes of the E-jets installed along with the IAB and HSAB. No markings visible like on holleys .I am hoping Tuner or one of the other carb gurus will chime in with their thoughts. Dan

[PRH]

I doubt 5 active emulsion holes per venturi is the hot set up.

I wonder if the Holley or QFT bleeds fit/work in those blocks.

[6.50camaro]

OK ,My bad. I just went to check the thread size and pulled out a couple jets and found #2 and #4 or not drilled thru just drilled part way. The threads are 6-32 . Found a tip cleaner and #1 and #3 .027 would go thru but .031 would not quite go thru. #5 .031 would go thru but .033 again not quite . I didn't want to force them . So it likes like the E_jets are std calibration. Dan

[BradH]

Misc things off the top of my head...
- BG emulsion bleeds -- IIRC -- have a smaller diameter shoulder than QFT e-bleeds... don't remember if QFT will fit my BG Gold Claw blocks or not
- There are one or two eBarf vendors selling old stock BG blank bleeds... at a premium IMO; too bad the passages are drilled all the way thru, vs leaving a step so you could use cheap 6-32 set screws like BLP
- QFT pre-drilled bleeds are done by blind monkeys in the dark; if you use them, buy 'em blank by the 10-pack and drill your own
- Holley e-bleeds may fit BG blocks, but are priced absurdly... something like $10/pair last time I looked
- BG's as-delivered tunes for many of their race carbs were odd, or simply bad; lots of "too rich down low, too lean up high" complaints
- My BG Gold Claw (predecessor to Race Demon RS) was originally member PRH's carb that he flogged on the dyno for a couple of different venturi & booster combinations
- For the 1.562" venturi down leg config, he used .026" MAB; I'd have to dig up my notes to see what else he spec'd cuz I never ran it in that configuration
- If you're changing emulsion, etc., without being able to see some AFR #s just to get a feel for the trends, you're flying blind
- There's a Demon tuning book that was put out about 20 years ago with details of the differences across the various carb lines (but it pre-dates the Mighty Demon series) that you may find helpful

[BradH]

A FWIW re how my metering blocks are set up "for now". The emulsion bleed stack is a new baseline from which to see if my suspicions on where there was a lean swing seen during an older dyno session are correct. Keep in mind this is a 1.425" venturi down leg setup, not a 1.562".

[Alaskaracer]

For emulsion bleeds, IFR's, and air bleeds you can use brass set screws from McMaster-Carr. They are cheap and you just need a pin vise with bits to drill them. Best way to go when doing carb tuning....

[BradH]

Anybody tried staking, or some other method, to create an interference fit for a set screw to keep it secured when used as an e-bleed for a metering block designed to used a shouldered screw?

[6.50camaro]

I have never got into recalibrating meter block before, always just used Holley's factory calibration. If I under stand right the higher Ejet on the metering block the lower in the rpm range it effects. If that's the case then the typical Demon calibration I've read about of rich down low and lean up high would mean a larger orifice high (#1) and smaller down low (#5). If I have that right then, would swapping #5 .033 with #1 .031 be a start in the right direction ? Dan

[BradH]

I know you're looking for simple yes/no answers, but I don't have them.

If you want to start with a basic emulsion stack baseline from which to experiment, .028"/plug/.028"/plug/plug (a "traditional" Holley config) or .028"/plug/plug/.028"/plug to spread it out a little more.

Here's a bunch of stuff I've kept on the subject that gets far deeper into the topic than you probably want to go, but is actually beneficial in getting a better understanding of it. Hopefully the links cut-n-paste w/o breaking them.

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This forum is a good place to get into more in-depth carb tuning "stuff", and there's a dedicated Holley (and Holley-like carbs) section: http://racingfuelsystems.com/viewforum.php?f=4

Mark Whitener: “You have to understand the reason for an emulsion system. Take your C&S Aerosol billet carbs, they do not us a booster, they use a discharge tube. There is no emulsion used, save for a very small main air bleed and one bleed above float level to act as a kill bleed. A tube senses airflow at a one to one ratio as the pressure difference or vacuum increases, so fuel flows in a direct proportion to the airflow thru the carb, so only a main jet is needed to set the correct amount of fuel. A booster however does not flow one to one, it flows in a straight line as pressure difference or vacuum increases, however the airflow curves towards a horizontal flatline.

As a result an air correction system, emulsion, is needed to allow the booster signal to follow airflow. And it is there mostly for air correction, emulsion or emulsified fuel is a result of the air correction, and should not be relied on to emulsify the fuel. This is where some carbs go off the deep end.

The second part of the air correction/emulsion passage on a standard Holley 4 barrel is that it holds fuel, so as air is pushed from the main air bleed down the well the fuel is pushed out of the emulsion bleeds, making it an added acceleration circuit. Remember this.

So what happens is as the signal becomes strong enough to start fuel flow it also tugs on the emulsion passage. Any bleed above fuel level will delay the start, and will depend on the total area of the bleed or bleeds and the size of the main air bleed. This is where bigger and smaller main air bleeds can delay or speed up a little the start. However once the fuel flow starts the large bleed can actually fatten it quicker, allowing the fuel in the emulsion well to be pulled faster into the mainwell. This can make it excessively rich early with a larger bleed, and combined with a lot of emulsion goes off the deep end. Then as RPM's and demand climbed it shoots the other way, goes lean. I see this when more than 3 bleeds and over .028" emulsions, and over .030 main air bleeds. What also happens is the air goes thru in big slugs making the fuel curve choppy, fuel is not mixed well with the air coming into the mainwell. It leaves the booster in spurts rather than an even mix. Once the fuel is depleted to the bottom open emulsion hole then it just feeds air, until the throttle is closed and the mains stop, and the emulsion well is allowed to fill again.

So what do you want to accomplish? It depends on the application, fuel type, engine demands... What I find is when you use a booster that atomizes fuel well to distribute fuel evenly you don't need any more air than what is needed for correction. For most gas carbs on the street a kill bleed and two .026-.028 holes spaced to go about half way down the well is plenty. I like smaller bleed for racing, and usually space three smaller bleeds. And if I can control the kill bleed size even better. With alcohols and oxygenated fuels, or big engines with two carbs you can place the bottom bleed all the way down, use all the fuel emulsion well. I set most race carbs up this way, but with a small bleed usually at .021 or smaller. I have a blow thru I reworking that will likely get a .021 at the top for a kill, .024 all the way at the bottom. And a last piece of this puzzle to remember is that at WOT the idle circuit that usually pulls from the bottom of the mainwell can now become a bleed into the main circuit, adding more air in....

Now with E85 you have a significantly different fuel in the mix. Too much air makes it stupid rich early, lean at the top. I've seen it chased on a dyno... once emulsion was set small it cleared things up. For E85 go real small, I've got an RS Demon that has .014 in the top, .016 third and .018 forth with the second and fifth plugged. For the Dominator get the top small, .014-.016, and .020-.021's in the third and fourth or third and fifth on 5 hole blocks.”

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https://www.tapatalk.com/groups/racingf ... g-t42.html

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An older Japanese research paper from the 1960's that has some interesting experimental vs theoretical testing results:

"Effects of Air-Bleed Systems on Carburettor Performance"
Yasuke ASANO, Toshitaka CHUMA, Heiichiro HAGA, Tadahiro MOCHIDA

Overview: https://www.jstage.jst.go.jp/article/js ... 1/_article
Download: https://www.jstage.jst.go.jp/article/js ... f/-char/en

It turns out there is also a "sequel", although I haven't found a copy that's been translated into English. Even though it's still in Japanese, the diagrams are presented in a similar manner to those in the original paper. I have figured out most of - possibly all - the diagrams, but haven’t documented it anywhere at this point.

"Effects of Multihole Air-Bleed Systems on Carburettor Performance"
Yasuke ASANO, Ichiro ISOBE

Overview: https://www.jstage.jst.go.jp/article/ki ... 6/_article
Download: https://www.jstage.jst.go.jp/article/ki ... f/-char/en >> IN JAPANESE <<

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I've been told this older paper has some good info, too. However, I have to admit that every time I've started to dig through it, my eyes glaze over:
NACA TR 49 - Metering Characteristics of Carburetors —> https://www.abbottaerospace.com/downloa ... rburetors/

[6.50camaro]

Thank you Brad H for your time , explanation and links . I see I have plenty of reading to do now. Dan