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I was told the signal is optimized for dual carbs or single carb.

The experts should have much much better explanation.


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When I went from one carb to two, there was a little tuning involved, but not much. Biggest thing was to make the carbs both the same and when you make a change, you do the same change to both. Have since gone to injection (mfi for alky), but still have my carbs.

 

Jetting may be quite different for each cylinder/runner. Weston dynod one and every jet was different to get EGTs closer and it gained several HP.. 10 sizes different.

 

The common difference is the linkage ratio, as with the carbs crossways most tend to use 1:1 linkage instead of progressive. - That said though, I have the progressive linkage in my pair to lessen how touchy the throttle is with my pedal ratio/linkage.

Beyond that a good custom set will likely have the idle fuel and air bleed circuits metered differently, as you have 8 idle circuits instead of just 4 yet the motor is still going to want the same amount of fuel at idle as it did with just 4 circuits.

 

 

Check the specs. between the 1 x 4 and 2 x 4 carbs on the Holley web site.

Dominator

Designed for NASCAR, but now Dominating many forms of racing! The ultimate big bore racing carburetor!

www.holley.com

 

Might want to look into a set of these.

Quick Fuel 16-13-10QFT Nitrophyl Float Wedge Primary

Nitrophyl Float Primary Wedge - For circle track use on the primary bowl. Also used on 2X4 setups, allows fuel to move to the back of the bowl and not shut the needle off by raising the float. 10-Pack

www.holley.com

Quick Fuel 16-104QFT 2x4 Drag Race Float Kit

2x4 Drag Race Float Kit

www.holley.com

 

Thanks for the link. I need to freshen my carbs this winter.

 

Good info guys, I also got a killer deal on a pair of SV1's that were matched on an engine already but I'm still not completely sold on them. I don't want to spend the first 10 plus passes trying to figure out the carb tune, I'll get enough of the trying to introduce 2 foggers together.

 

Squirters are smaller too

 

Look into APD or Pro Systems. I'm switching to a sheetmetal tunnel ram with two 1150 APDs here in a couple of weeks.

 

I use 2-circuit carbs on single set up and 3- circuit carbs on dual set up. I ran a pair of 1150 holeys on my 540 with a off the shelf holley intake and was very easy to tune coming off the trans-brake and 8100 in the traps.Also got a nice idle around 900 rpm. This was in 1992 and don't know how the modern carbs are for quality thou.The 3rd circuit is supposedly for transbrake rpm and a clean leave,worked for me.Tom..

 

PS I am sure 1050s are too small for the 598. I would check on that size carb with some knowledgeable person. Tom..

 

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That's weird, I was told to use the 3 circuit on my single dom engines, and the 2 circuit on my tunnel rams???


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I put a 3-circuit on my 548 street Monte (by mistake) 1050 cfm and I chased that damn thing for two summers.It still doesn't perform as good as the 2-1150's on my tunnel ram 8100rpm( max ) 540 race engine. And maybe that's the clue,maybe the 3-circuit is calibrated better used in pairs on the tunnel ram. I even had a holley guru come over and work on 1050 and he couldn't get any closer than me. And after messing with it for several years and being tired of fighting with it ( I have oxygen sensors on it) everything was pretty good except high rpm went lean. Put 100 jets in it and still went lean. I was on the Team Chevelle sight and posted about it and a gentleman by the name of Mark from Fla. told me to drop the high speed air bleeds down about 18 sizes. Seemed risky but he works on these carbs ,his business,so I tried it and low and behold it was super rich,100 jets still in it,.Worked the jets down to a reasonable size and the AFR came right in. Great! so off to the track we go and after 1 pass the trans blew again,4 th. time for that, 4L80E, now my trans guy won't even work on. So it's been in the barn for 4-years,i'm pissed at it. And so it goes.Anyway The intermediate on the 3-circuit is suppose to work with a trans brake and or tunnel ram.Mark from Fla. said the same thing that the 2-circuit would work better on the single carb,said he could convert it to a 2-circuit at his shop,or he would sell me the parts and I could do it. It runs pretty good and I'm still pissed at it and don't have a trans. I'll worry about it later. Tom.. PS. Sorry for the book length version.

 

This float might give you a little more room for fuel.

Quick Fuel 16-14QFT Nitrophyl Float (Road Race)

Nitrophyl Float (Road Race) - molded wedge on both sides to control fuel when turing right and left! Alcohol compatable.

www.holley.com

 

Don't really need 3 circuit dominators on single carbs with transbrake use unless maybe throttle stops. Mostly "more is better" mentality promoted by Holley, (like 5 emulsions is "better" than the original 2 that worked fine.) When annular boosters came along on 4500 carbs, it was for very limited applications for tunnel rams and individual runners, which did not last long. The annular boosters were carried over as they helped and the 3 circuits just came with them. Dominators as big as 1250 singles work just as well or better as 2 circuit than the intermediate 3 circuit and are simpler to tune. (Just my experience.)

 

If you use a PV, that adds another curcuit, if you keep the float bowls full, why do you need more emulsion "holes", if you use a "larger" needle and seat you can use less fuel pressure.

 

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My 468" & 557" both used the 3 circuit 8896 and they ran excellent.
The 468" used to get tons of attention it ran so well, 9.30 at 3000 lbs,
small tire car with crap 60' times was getting it back then.

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I used a three circuit dominator at first when it was a single carb. Had some serious tuning issues. When I got it tuned so it would run without fouling plugs down low and loading up, I couldn't get enough fuel to it on the top end....converted to two circuit, problem solved. When I went to duals, two 1295 king demons, never even tried three circuit. Both converted to two circuit, easy to tune, responsive, and great drivability part throttle. You don't need three circuits on anything we do.....and most three circuit carbs are way out anyway....Dave Braswell uses 4 or 5, but he's also changed where the discharge tubes are located in the throttle bore, which affects when the circuits become active, along with other changes......BUT......If a carb is properly matched and properly tuned to the engine its on, there will be little if any difference in performance going from one carb to another, keeping the same criteria...

You don't need a 3 circuit....two works perfectly and is easier to tune....

 

Biggest difference is in the idle/transition calibration. Main jets usually end up being smaller than with a single. And I still like 2 circuit over 3 for almost all applications. Stick with dual 4 barrels, the one hole wonder will most likely keep you wondering...

 

3 circuit was designed i thought primarily for the two speed trans. Has richer intermediate circuits to over come the bigger rpm drop.