2-circuit, or 3-circuit Gen-3 Ultra Dominator?
 

I'm planning on getting one of the new Gen-3 Ultra Dominators (1050 CFM) for my 427 CI, SBC drag race engine which makes about 660 HP at the crank. And, I'm not sure if I should go with the 2-circuit, or the 3-circuit version. Sometimes I foot-brake the car leaving at 2500 RPM in No-E and in Super Comp I leave on the Trans-brake at 4000+ RPM. So, what does everyone think; 2-circuit, or 3-circuit for my application?

Warren,

Go over here and join. Lots of good info on carbs.

http://racingfuelsystems.myfunforum.org/index.php

Pro systems SV-1 . . Solves all the problems Holleys have . . Very simple. Two carbs, one on each end, literally, with one big hole in the middle . .

It's Magic, it very seldom needs a jet change (if ever) and it does it's job every time . . No misses . . It doesn't care about air or weather. Never seen anything as simple and works so damned good!

Buy it new, from Pro systems and let them set it up for your engine. You won't be sorry . .

Thanks Curtis, I've already signed up!

A 2 circuit is what I suggest, and I have a few out there running in the Super classes. They run well on the stop, yours makes about what my 23 degree 427 makes. Either the Quick Fuel or Holley will work, either may need fine tuning to suit your engine. You are signed up, check the for sale section out as well...

One more time on the SV-1 . .

We've had it on top of three different size engines, 6 camshafts and raced at altitudes from 3800 feet to 6200 and never touched it on Gasoline. This last season we sent it back and had it converted to alcohol and the only "Tuning" it needed to run a "9 Teen" was fattening up the idle air jet . .

It literally takes the carburetor (and the guess work) out of the tuning picture . .

And we've used it with and without the Biondo SLE, so it doesn't care how you leave the line, or what you do once you have . .

I've seen the other side, two different ones on a dirt track engine on an inertia dyno and it wasn't pretty. One local runs one, tells some it's great and tells others he can't get it right...

I've ran the new 3 circuit one, it was decent. Still no where near as good as the APD 3 circuit.

I've sv1's very few have great luck with them. The tend to stumble a lot around here. Just from observation, how do you control the fuel splatter going WOT from the squirters, it splatters all over. Not being a smart a$$ just wondering if anyone else has seen this ?

Is'nt that the issue when the Preditor carb came out?

Never seen a problem with that. It does seem kind of like old fashioned shower heads, but in our case it all goes down that big old hole . .

We've run the same SV-1 on a 468, a 498 and a 582, on Gas (VP-116), and had two different cams in both the 468, and the 498, along with the current 582, and we've never had to make an adjustment from the original setup the carb came with. The thing is so simple there ought to be a law against it, and if you have any "Holley Smarts" at all, diagnostics are easy. The biggest problem, going back to the "Holley Smarts" is, you have to be careful with the SV-1 or you'll overthink the problem.

Let me add, we haven't had to touch the Jetting, no matter the altitude or air density, or the fuel. The engine demands and the carb provides . .

We sent it back to Pro systems when we made the change to Methanol and they "opened it up" for alcohol, and sent it back with a new Fuel Regulator that works in conjunction with the engine vacuum, so that when vacuum drops the fuel pressure goes up, keeping the float bowls full . . Works like Magic, but you have to adjust the regulator a tad when air density (Thus air pressure) changes. That's kind of "Round by Round tuning" but it's the only thing we really have to watch.

I'll add that we do have all the bells and whistles, EGT monitor (#1 & #8 ), and a run recorder for pass by pass data, so we're pretty aware of how well the engine is working . .

The only problem we've had with it was, when we got it back from the Alky Overhaul, we discovered the car wouldn't idle worth a d@mn once it was warmed up, and wanted to stall when staging . . We were at the track, and overthought the problem . . Fussed with it until about 9:45 pm MDT . . called Tech Support and left a message, and within ten minutes, the CEO called us back (Midnight in Florida) and listened to our description of the problem, told use to fatten up the Idle Bleed Jets on the front system and told us to call him back if that didn't work . . It did and we've had no other problems.

As far as I know, in all the years of racing, I've never been able to call somebody that sold me any kind of speed equipment, on a Saturday night at 10 o'clock and got anything more than a hate call on Monday morning. Of course, for the most of that time I didn't have a phone in my pocket either!

Nonetheless, that's really service! I don't think Barry Grant would pick up the phone if I bought a system from him and had problems with it. Not that he's a bad guy or anything, it's just that most companies don't offer tech support to a racer on the weekends . . And those that do, most often don't offer contact with the Designer and CEO . . .

Now, let me qualify everything I know about Carburetors and Drag Racing. Not much. Most of my life has been spent fussing with Hilborn and (mostly) Enderle Fuel Injection. Always thought a carburetor was the Oddity on top of the tow truck's engine . . But, For many years I've listened to those who use Carburetors and learned one thing if nothing else.

"A Used Holley Carburetor is somebody else's mistake that they can't fix, so they sold it to you!"

95% of the time!

And I'd bet that goes pretty much for any other Carb off a race car . .

[quote="roadkill2"
"A Used Holley Carburetor is somebody else's mistake that they can't fix, so they sold it to you!"
95% of the time!
And I'd bet that goes pretty much for any other Carb off a race car . .[/quote]

Carbs are quite simple, and when they are calibrated and sized correctly they work as they were designed. It's when they are plundered by those that think they understand them that it becomes an issue. A fair amount of time the problem isn't even the carb, and even if it is most of the time it's not too tough to fix. A used Holley is a gem to someone that takes the time to understand it. Same goes for a Demon, nothing a little massaging won't fix.

Holleys are pretty simple pieces, but you just have to look for hammer marks, saw cuts, grind marks and all those little things that indicate that someone up the ownership line understood other ways of making one work . . then it's time for Burial rather than "massaging" . .

And true, carbs don't (often) wear out. Usually a carb gets blamed for something else that went wrong all of a sudden. Most of the time it's a 'Lectrical Gremlin . .

On a Holley, that's just about all that can "Wear" out, save for an occasional Needle and Seat . . or a disintegrating pump diaphragm . . Anything else is either contributable to dirt or human . .

I'm wanting to upgrade to a Dominator and I really like the looks of the new Holley Gen-3 Dominators! I know there are many good carbs on the market now days and ton of people who can upgrade and customize carbs. I also plan to go with an Edelbrock 2970 intake that has the cloverleaf plenum and I plan to clean-up the runners and plenum myself and use one of the HVH Cloverleaf Super-Sucker spacers.

When you buy any new carb, it's your's to do whatever you want to do with it. A used one? You don't really know.

But,if your carb's jetted right, and is working as designed, you seldom EVER have to mess with it. If your Jetting is right for where you live, then it'll work fine anywhere else. The more air, and the denser, the more fuel it will pull through the systems, so you shouldn't have to mess with anything except the idle circuit tuning . . If you do, then you have something else wrong with your tuning combination!

But again, that's only what all my past mentors have had to say about a Carburetor . . In the last 4 years, now, all my experience has been with the SV-1, so I'm no Holley Expert!

2-circuit
 

I think if you like the looks of the new gen 3, then that's what I would go for. If you have money to purchase it, then be prepared to spend a little more to have it customized if it needs it by someone that specializes in throttle stop carbs for the Super classes.

As part of my hobby of racing, I have been building engines, rear ends and carbs for years to support my cash flow needs for the racing. I buy good used brand name carbs, rebuild, do minor upgrades and then find racers who want them over new carbs because of price.

I have had about every brand of customized carb and a bunch of throttle stop carbs. It seems the throttle stop carbs all have a common theme, intermediate circuit leaning or elimination. I assume this is to accommodate the time on the stop and coming off the stop. They all seem to work great as bracket race carbs too. There may be more than just changing the intermediate air jet to make a good throttle stop carb.

I prefer to get 3 circuit carbs and then lean out the intermediate circuit, and perhaps have to richen the main jetting. 3 circuits also seem to have better resale value as most people don't realize a 3 circuit can be rich on the fuel curve.

In your case, the 2 circuit may be a good choice for throttle stop racing as mentioned in an above post by someone who knows a lot more than I do on this subject.

If you want to see the most exotic throttle stop carb, look on DaVinci's site at the SPIDER 1050 and 1250. He completely eliminated the intermediate circuit and them added HARLEY motorcycle custom jet pods above the main boosters to bring in the new intermediate circuit after the main circuit was already in, above 5000 RPM. It has jets in the pods to tune it for the throttle stop. I had one and it worked great. But it had external fuel hoses that I was a little uneasy about. Not sure if he makes them anymore. And they were $1895 new.

What carb are you currently running? If your stuck on the Gen 3 look, go with the 80902 2 circuit 1050.

I’m currently running a 1000 CFM, 4150 Race Demon (not sure it actually flows the rated 1000 CFM), which was built just before Barry Grant when out-of-business (maybe 2010). Additionally, I’m not running a throttle-stop, primarily foot-braking it and running it wide-open!

I’ve seen several posts with suggestions for different carbs (person preferences), however, I haven’t seen any compelling “technical criteria” exactly when you should run a 2-circuit, or 3-circuit carb.

2 circuit
 

Guys, correct me if I am wrong.

Originally the annular discharge, 3 circuit dominator like 9375 was designed as a tunnel ram 2X4 carb combination. 3rd circuit was to help cover up the flat spot on a tunnel ram with their big plenum volumes.

Then someone,(anybody know who?), found out the annular discharge boosters were better for some single 4 applications and the 3rd circuit just came along for the ride. Now all Dominators are Annular discharge but you get the choice of 2 or 3 circuit.

Don't really need the 3rd circuit on any BBC unless tunnel ram? Maybe still needed on SBC?

Re: 2 circuit
 

Very good info!!! I noticed they show the 3-circuit for the 1x4, single carb application! My gut feeling is to go with the 3-circuit for my application.

Actually the intermediate circuit was derived from metering blocks used in a Chrysler emission carb, the application was to use them on individual runner intakes where pulsing below the throttle bore is high. 4 and 6 cylinder engines can suffer from this, it disrupts booster signal at lower RPM's. Dominators running methanol can benefit as well with the right 3 circuit blocks (not factory blocks with the idle tube in the mainwell), not so much because of booster signal issues but as a supplement to the main fuel as passage sizes are on the border to pass enough methanol. For a V8 on gas it's rare an intermediate circuit is needed at all if you calibrate the carb correctly. Plenum intakes dampen pulses so there is no hole to fill when tuned correctly. I have run up to a 2.400 throttle blade billet carb with no issues running the intermediate circuit plugged. That carb flows over 1800 CFM...

2 circuit
 

Thanks Mark, I knew you good for the correct info.

This is what I found on the Holley website, contained in their Dominator instructions.

Inclusion of this circuit was required as a means of obtaining a smooth transition from the idle to the main metering system. It is intended to overcome a dip in the fuel delivery curve of the Model 4500 carburetor. Increasing/decreasing restrictor size delivers more/less fuel to enrich/lean the mixture for transition.

Except there is no dip when the carb is set up correctly. Idle, transition, and main metering can be tuned to provide a smooth transition without it. The only reason it was added originally was for individual runner induction. Marketing told them if is two is good, three is better and will sell more. One for the bean counters.