Great post man!

are you using the Race demon carb? Im running a Race demon 1050 DR(RS)... almost 600hp but still too much carb... im was gonna re-sleeve it to a 775cfm, but im using the downleg boosters...

do you think it would be a good idea to go with the 825cfm sleeve and install the annular boosters?

you seem to know your stuff, and im new to the demon scene and always looking for tips/advice from people that arent afraid to dive right in and do it.

also, if you are using the Race Demon, like someone said that the Race demon is the only one that can be screwed in, i was wondering if that is true?

Thanks for your time man.

JOe

 

Joe,

Only the Race Demon, and RS Race Demon series come from the factory with screw in boosters. The other series carburetors use swedged in boosters. As far as what size, sleeve/booster combination to go to we'd need some more specific information about your combination.

Technical Support,

Barry Grant, Inc.

 

This is a great post and very interesting. One thought comes to my mind though..............If the performance is improved so much by this change, why don't all the other model carbs come with the same capabilities as the Race Demon? Is there some tradeoff when making the change that hasen't been mentioned (like economy or drivability on the street)?

 

There are pros and cons to annular boosters and down-leg boosters, its a matter of which is going to work best in a given application. It would make our job much easier if there was one that was best all of the time.

Now as far as having the ability to change the boosters with a spanner nut the reason we only offer that in our Race & RS Race series carburetors is due to cost.

Technical Support,

Barry Grant, Inc.

 

My 825 Race Demon flows 975CFM according to Barry Grant so I would imagine that the RD 1050 RS is flowing alot more than 1050CFM. So when I put in the the annular boostesr it probably knocked my overall CFM rating down substantially ( because of the size of the boosters ) but I would only be able to see if it adversly effected top end on a dyno or 1/4 mile, which has not been done as of yet. In the magazine test the annular booster carb picked up both HP and TQ over the downleg booster carb, so go figure.

YOu can look at the specs of the Demon carbs here :

http://www.barrygrant.com/demon/defa...e=29&specs=29q

You probably want a little smaller carb so if you look at the venturi size you get the idea of what sleeve to use with the annular boosters to get the size of the carb you want. Keep in mind that these carbs are not rated the same as Holley cfm wise so a 750 Demon flows alot more than a 750 Holley

 

Motorhead - I was looking at your pictures. You and I probably have the same Powermaster alternator.

The alternator came with a warning about max RPM of something like 17,400 rpm. I changed to a bigger diameter alternator pulley because i have a higher rpm motor that could exceed the alternator rpm very easy. Do to the damper pulley ratio.

Maybe you should look at it also.

As to the annular booster I went to a local carb only race shop with that Car craft article. I had also contacted BG about the cost of having the annulars installed on my 750 speed demon. This shop has a circle track test mule motor to dyno carbs before returning them to the customer. He also has flow benches. That article was bought and paid for by BG just to generate revenue.

The annular does in fact work better for a low RPM motor. Well your motor and mine have too big of a cam, heads, RPM range to even attemp to correct the fuel curve below 2000 rpm. Once you get over 5000 rpm the annular is more out to lunch than that article really shows on the HP graph. It does state that they couldn't get the jetting right. NoS$it! Because the fuel curve is all AFU at higher rpm.

The shop said that he could mod my speed demon and show me the flow bench and dyno it on the circle track motor with sniffers to show me the results. Just don't buy into every car rag article

 

gkull,

You may want to get your facts straight before accusing anyone of “Buying” an article. That particular article was written by Jeff Smith who is one of the most respected writers in the industry, and the only we had to do with it was that we supplied product for their testing. We had no control over the testing or the outcomes.

Stating that annular boosters only work on low RPM engines and have poor fuel curves would be another false statement. We routinely use annular booster carburetors on engines that turn well in excess of 10,000 RPM and tune the fuel curves accordingly.

As stated multiple times in this thread there is not a right or wrong booster, it’s a matter of which one is going to work in the particular application based upon Venturi size, engine/driveline specifications, and vehicle usage.

 

One thing for certain is that the annular boosters are going to cut air flow for the simple reason that they are physically bigger than the downleg boosters. That is why if you had a carb that flowed the exact correct CFM your motor required at max RPM then you switched to annualar boosters you would not be flowing correct CFM for your motor.

I wonder how many are running a carb that is the exact correct size, or even if they are in the ballpark ? Because mine flows 975CFM (and a 850 Holley would probably be OK on my motor ) then the annular boosters are not going to cripple my motor up top.

LIke I said I have not dynoed the motor since the change but I do know I can feel more power in the lower RPM's and to be able to feel it in the seat of your pants, it's a substantial gain. The throttle is crisp and responsive, I cannot imagine trying to get the "driveability" any better. It is like driving a stock cammed motor around with 550HP, I would not believe it if I wasn't driving it.

 

Don't get me wrong - I bought demon carbs when they first came out because they really did have some nice features.

But just like anything out of a box, you have to fight with adjustments and things just wrong from the manufacturer. I just happened to get the 750 speed demon made on Friday or something. It had the major off idle bog. So I had to dork with everything including drilling out the primary squirters and replacing the little accelerator pump flapper valve. All in attempts to get it to squirt right

It did not occur to me that some moron at the factory installed the Pink accelerator cam wrong on the primary side. It was installed screwed into the bottom hole so it didn’t even move the arm until you were way into the throttle.

I also had to drill out all four throttle blades on both of my demon carbs before the four corner idle adjustment screws could get lean enough to actually work. You guys corrected this problem in the later models.

What I was saying is that an annular booster is not a cure all for big single plane manifolds in combination with big CFM heads and cams. A motor that has low vacuum and idles at 1000 rpm is just not made to run well under 2000 rpm. So with booster changes it can be optimized for low rpm which is really kind of useless if your whole system isn’t designed to run that well at lower rpm in the first place.

As to your 10,000 rpm statement. In my lifetime of being around racing I have not ever seen a 10K rpm stock block chevy. I have be the proud owner driver of a 9000 rpm dragster and it took a lot of money to make it reliable. So when some bubba tells me about his 10k rpm motor I can say because I know first hand what it takes.

 

That is the thing, there isn't going to be an exact carburetor that works best for each combination everywhere. For most combinations you will have to have some compromise. For most cars you can get something that will work better down low, or up high, or drivability, or whatever unless you’re dealing with a specific race application that has a very small RPM window you’ll have to find what works best for what you’re working with. Also keep in mind that the rest of your combination can alter what is optimal. If you’re dealing with a car that has limited traction, decreasing some of the throttle response, and low end torque may not be a bad thing, but dealing with a short track car or autocross giving up some top end power in exchange for throttle response would be optimal.

Technical Support,

Barry Grant, Inc.

 

We apologize for the problems you had with your particular carburetor, as with anything assembled by real people mistakes can happen. We are continually working on our systems and processes to prevent mistakes from happening. As far as having to drill holes in the throttle plates that is an issue that was common on modular carburetors for decades which is why we came out with out Idle-Eze™ system in 2005 to eliminate the need to have to drill holes.

I never said that annular boosters were a catch all, there are many places were they are not appropriate, and do not perform as well. The only comment I had was based upon yours that we paid for that story, the only thing we did was to lend the writer some carburetors for testing.

Also, never said anything about a stock block turn 10+ these are DRCE pieces with thousands of Spin-Tron® hours to get there. What class are you running your dragster in that you’re turning it 9,000? I would imagine it would have to be some type of Competition Eliminator class, since there wouldn’t be any reason to turn anything else that high in most other classes.

Technical Support,

Barry Grant, Inc.

 

My 9000 rpm alki injected 359 ci motor was just your typical 360 class sprint car motor with a hotter drag race cam. 4.040 X 3.5 stroke 15:1 compression 2 1/8 inch spread port headers. Half filled block water jackets and only water in the heads with a pressure relief to a puke can. The injectors would have ice on them even on a 90 degree day while running and it was hard to get the motor up to temp. You had to have it running in the staging lanes before a burnout to warm the motor. If you didn't use the chute you just drove it back to the pits because it never really got much over 200 during a run.

It's class was Jr. fuel in Nastalga drag racing with 8.40s at mid 170 mph or at most NHRA events it was 8.90 super comp or quick 16 for bracket racing. It had near 1 second sixty foot times 1.05's

Years later on we got smarter and installed a 1000 hp 8000 rpm alki injected 509 ci big block chevy to run the 7.90 class as a low 7 second car. Its weight was only 1340 pounds. We sold it to some race team out of redding california.

 

gkull: On your alternator comment (not to hi-jack). I had the plastic fan on my alternator explode this weekend and it broke my hood, and the alternator burnt up on the way home...

I figured out the pulley drive ratio and the alternator was spinning at 20,000rpm when it let go. Last year I ran the alternator to 22,000rpm and it has been like this for 3 years... I personally am suprised it lasted this long, did not even think about it. I will be getting a larger pulley.

Wayne: Try a dominator... I have ran both a 750 and 1050 dominator on my 406 and the driveability was much better than my 750 Mighty Demon. However, the 1050 was a 3 circuit so the midrange was insanely rich.. The 1050 ran the hardest of them all, sadly I only had it for the weekend.

 

I also switched to an annular carb setup and wow what a difference. I was running a typical double pumper before the switch. It is truly like two different cars. Not to take away from any other manufacturer but I went with a Quick Fuel Technology 750 annular because it was best for me. I liked the price, customer service and the fact that I could dial it in with more precision. What I don’t like is there web page! If you need to get a new carb you should shop around and do some comparisons. This carb has removable (changeable) HSB, IAB, IFR, and 8 replaceable Emulsion jets per metering block plus all the typical changeable stuff. With all that adjustability if you cant get it setup correct you are doing something wrong. Now I just need the wideband to dial it in. Going to the Dyno on the 15th.