Trying to decide which to buy. Would be 950 for a 557.

I don't think there's an Edelbrock that's going to come close to feeding a 557.

Demons, I've heard a slew of issues around them having casting flash and crap in their feed channels. Too many stories to trust them. Many guys have had good luck I'm sure, and the billet metering blocks and throttle plates have to be a good thing.

Holley, is the "standard". I don't think you can go wrong. I have a 950HP that has been great...I'd definitely look at getting a "custom" carb from somebody like Quick Fuel or Pro Systems. You're going to pay a good chunk of change for a 950 no matter what, it probably wouldn't be much (if any) additional cash to have a carb shop hook you up.

Any thoughts on those "budget" race prepped carbs in the jegs catalog?

- Pumped Up! Fired Up! Super Excited!
Primerica Financial Services.......:-D

Are you referring to the Quick Fuels or the Pro Comps in Summit?

Personally, if I'm going to spend that kind of coin on another carb...I'd go right to Quick Fuel directly and have the carb set up specifically for my combo. Those carbs that Summit sells are nice with the billet parts, but unless you fill out some kind of spec sheet and send it to Summit...they're just going to be a standard carb. I'd rather call the place directly and talk to the carb guy that will set it up for you.

I'm no carb wizard, but when you talk to a carb guy that knows what he's talking about...you start to realize about all the tuning of the different circuits that these guys do...and how much they take into account things like convertor/gear/cam overlap. There is a TON of stuff that can influence how they tweak them. Add to that, basic stuff like deburring the main body, thinning throttle shafts..I personally think it's money well spent. I've seen a good Quick Fuel carb pick up 15hp over a $650 Holley HP on a dyno...wouldn't think that you'd see that kind of gain over what is already a very good carb, but it's possible.

...Usable "as is" for a lot of 460 combos, (well, except street/towing), or do the need some reworking.

I haven't owned such a combo, but I've ridden in, and driven some.

These were well tuned combos, they both were somewhat "sloppy" at part throttle...motor wanted to load up a bit and stumble under light throttle. One was a modified 1250, one was a box stock 9375 3 circuit Dominator. I'm sure a carb guy could clean up part throttle though. My friend running the 9375 will pull some jet out of the primary side when doing a lot of street running, that definitely helps clean up part throttle. My guess is that a carb guy could restrict the intermediate fuel channel to help things out without effecting WOT, but that's just a guess by a guy that knows just enough to be dangerous...but has very little practical knowledge of actually modifying carbs.

If you want a good dominator that runs well out of the box, try an 8082 dominator. They are a 2 circuit rather than 3 circuit. They pretty much need nothing done other than your typical jet up or jet down for best perfomance. But they drive excellent out of the box.

Generally the 3 circuit carbs such as the 8896 are the ones that need more tuning. They normally don't run very well at part throttle out of the box.

You would think the 3 circuit would be better but in my oppinion it's not the case.

I had a 3 circut Dominator on a Cleveland and it idled great & ran faster using nitrous when compared to an 850 Holley I tried on nitrous. But straight motor the 3 circut Dominator had a dead spot or sag in the first 60 ft. I got some annular boosters for it from Barry Grant. They said this style booster would help with this problem (better signal), but I never got to try them.

For that 557 you want as much flow as you can possible get from a 4150 style carb. The best flow per dollar is the 850 mighty demon. They run about $500.

But as Chilly said, there are people out there who have had quality issues with Demons in the past so that's something to keep in mind. But others have had good luck.

If you're going with Holley, then per dollar a 4781 850 double pumper is hard to beat. You can find them on Ebay used or rebuilt for $150-300. An 850 holley has as big of venturis as any 4150 carb out there so don't underestimate how it can run.

True a 950 is considered to be a great all around carb if throttle response is a big concern, because they actually have smaller venturis than an 850 but a smoother enty on top. But with a 557 ci, throttle response and torque would also be in abundance with an 850 holley and it would run just as good at higher RPM.

If you want the ultimate carb for your combo though and you're not afraid to spend the bucks, go for a HP1000 Holley. They are pricey but they flow the most air.

I guess there are alot of options but it just depends on how much you want to spend.

I'm running one on my engine with no problems and perfect tuning. Bought it on Ebay new on a best offer deal for $485.00.
My engine builder has found that Demon carbs have a better and smoother fuel curve on his dyno than any Holley carbs he has tested.

Dave

DAVE-1977 F150 shortbox 4x4, 545 Cobra Jet that kicks butt in the mud. I also have one of the 1000 1976 Starsky & Hutch Gran Torino LE's w/ factory 460 patiently waiting for a restoration.

I think they were around 1000 CFM.

I have a couple which I've tested with; one is conventional vaccuum secondaries and one is converted to mechanical secondaries with Annular boosters in the secondaries.
If you are using a two-plane intake then they are a great addition and both work exceptionally well however, when used on a single plane intake at higher RPM, the third cylinder back on both sides, (3 and 7 on a Ford), tend to run lean. I've tried all kinds of fixes including different plenum mods and even raising the carb with spacers 4". The problem still continues though not as bad so, use 'em on two plane intake manifolds with the divider notched.

I have a 3 barrell 950 vac which has 50 CC pump. It hits the intake so I need a small spacer. Since it going on a shaker Torino Cobra I can't lift it much. Do you think I would ruin a good intake if I slotted it so the secondary butterfly won't hit? It's the SCJ style intake but it came from a boat. Only difference I can see in them is the nipple that goes to the waterpump is threaded.

Chilly & Mike could not have summarized this better. I've personally had Edelbrock 800 (joke), Holley 4150's 850 DP, 1000 HP and 4500 series 1050 3-circuit and now run a 8082 1050 2-circuit. I also own a wide-band O2 sensor which reads instant AFR from 11-18:1. Man-o-man......I've spent alot of money.........The Edelbrock is a junky cheap carburetor, and I believe the 800 cfm is bogus figure. I've never measured it, but its junky. The 850 Dp is great bang for the buck, with choke removed. The 950 is, like Mike said, good AFR curves through out the throttle range, and works great on street strip 466 in my opinion. The 1000 HP ran great all around, and was probably my favorite carb. Ran great, changeable air bleeds, which help immensely when tuning idle/transition AFR. Supports up to 650-700 HP ballpark. Regarding Dominators...I've spent alot of time tuning them on a 466 street/strip. The 8896 3-circuit is VERY VERY rich on intermediate circuits, and the int air bleeds have to be opened as much as .025" to get the AFR anywhere near 13:1. These really require restricting the fuel in this int circuit. The fuel jets arent changeable on the idle or int circuits on this carb, so barring inserting fuel restrictors, air bleeds are only way to tune these lower circuits. The 8082 is definately streetable on 466, just open idle air bleeds about .002-.005", and the best way to run is to drop main jets down to 84 range and open the power valve restrictors to .093". These ballpark numbers work vell on my 8082 1050. It will have light-load AFR in vicinity of 13.5 - 15:1, and WOT drops down to 12-13 range, which is where you want to be.....I agree Holley is way to go. Never had a Demon buy dont want to give Barry Grant a grand for a carburetor.

a down leg booster carb.I have a 1000HP annular booster carb on my 466 and wandered if my carb is set up close to what your carb was set up.

Thanks Mark.

...I run the 1000 annular on my 521 pump gas motor. I know everyone will scream 950 downleg. I bought the carb pretty close to new on e-bay for $500 and it had been "level 2"...definately been flowed...haven't touched it since I bolted it on aside from a small jet change.

As far a comparing an Edelbrock and stating it as junk is clearly a misapplication. I have run these carbs for 10+ years on mild street engines...and in my experience they have always performed very consistent and efficient (as what they are intened on a BBF) regardless of conditions. Anything over 400-425 hp run a Holley. Just my .02.

Rick

If it were me I would have a carburetor built for your application by a good carburetor builder who knows his stuff. A properly built carburetor will have many of the same features as a stock Holley or Demon but it will work at a level that's a notch or two higher than an off the shelf piece. Carburetors are mass produced items and so it seems that it's about impossible to build them to as tight of tolerance that's really needed when you want it right or even close to right. Areas like the emmulsion package, booster configuration, idle and transision circuits can all be improved and made to work much better than stock. Special features(950HP with a PCV port for example) can all be done on a built carburetor because it's being built for YOU.

As always, I highly recommend Bobby Oliver at Competition Carburetion as a straight up guy who knows how to do the job right. He builds a top notch piece that works great with no bologna... He's friendly and easy to talk to and he will give you the best advice when it comes to selecting a model that will work best for you. While his work is not cheap buying a carburetor through him doesn't cost much more than a new Holley anyway and he can also work from a core carburetor. In fact in some instances he prefers the older carb bodies you should see a few of the sweet pieces I've sent him over the years.... Give him a call at 775-331-5609..

if you're not going to do extensive tuning (preferably with a wide band oxygen sensor) on a production carburetor, then you should have one custom built for your specific application. I've always said camshafts and torque converters should be custom made to the application, but in some cases, the carburetor should be too.

May God's Grace Bless You.

1978 BRONCO: 508" stroker, TFS Street heads, A/C, Lentech Strip Terminator AOD-FRPP wide ratio gearset, Atlas II Highlander transfer case, performance built Dana 44/60-lockers & 4.10 gears, 4 wheel disc brakes, heim joint cross-over steering, 4" suspension lift, 35" mud tires.

what jet size are you running.

Thanks Mark.

Mark,

Cam: Ultradyne hyd. roller 236/244 @.050 .612/.612 lift.

Converter: 2,500 Hughes, flashes to about 2,800.

Gears: 3.50 currently a 2.75

Jets: 80 prim. and 86 sec.

Rick

I have an 850 that sits on a 429 in a dirt track car. The absolute best thing you can do to an Edelbrock is take the weighted air valve out of them. On my race car it would have a flutter at high RPM that felt like an ignition miss. A local guy at the track said he had the same problem and took the valve out. It made a world of difference. I've removed several from friends street cars and it made a huge improvement for them.

I've also got a very healthy big block in a Monte Carlo with a Demon 950. The only issue I had with it was the needle valves aren't that great but the Holley needle is a direct replacement. It has always been a great carb.

All the Holleys I've had seemed like I had to rejet them with every season change.

On the weighted valve, what is the best way to remove it? I looked at mine and it is down in there pretty far. I would like to take if off.

the carb and it can be lifted out. Makes a world of difference.

Soory it took so long to respond, I've been out of town.

I will take off the secondary weights, butterflies and shaft tomorrow. I have an 800 Edelbrock on a 466, and I do feel a good secondary kick-in on it now at WOT. I will see what difference it makes when converted to what is essentially a mechanical secondary carb by by taking the other set out. Thanks for the tip.

I took it off today, and it does wake it up a lot. In my case, now there is 1-2 seconds of mild stumble, but then it catches a lot stronger than before. Seems like a good extra 10-15 HP if not more. I am going to leave it off.

Any ideas on how to smooth out the stumble now? It is really not that annoying, but smooth transition would be better.

I also took out all the choke hardware. I did not have it hooked up anyway. Next step....cut off the choke horn and smooth it off.

Thanks for the tip, Tim.

John

It made a world of difference in the carbs I've removed them from. I havent noticed any bad effects from taking them out.

Tim,

I moved it from middle to closest hole in the pump shot arm...I hope this was in the right direction to give more squirt, but of course shorter duration on it. Still a slight stumble. I will try going to the farthest one just for fun. Although mild by most standards, I may have too much motor for it without going to double pumper carb.

I have a 466 with:
218/228 cam, 114 LSA
10 to 1 compressionm
Hogged out exhaust port D3s with 2.19/1.76 valves
1 7/8 headers full length
2200 stall on C6
3.27 gears
Torker II.
Car weighs 2900.

My Holley 1000 HP was downleg; I've read many places that Holley never really got their annulars to work as well as donlegs on 4150's....but I never has an annular. What i meant by the Edelbrock comments were this: I never flowed one of thesw 800 cfm's but I would be surprised if it flowed 800. The design is age0old Carter, and they were abviously good for quite some time, I just thought the whole carb, the finish and linkages etc were kinds cheesey compared to Holley. Thats all I meant. SV

I worked at Holley for eight years - many moons ago. The guys at Quick Fuel were coworkers and friends - still are friends. I tried one of their triple throwdown Dominators on my Engine Masters engine and it worked great. Responded to tuning and bleed changes and once dialed in it delivered a really smooth A/F ratio throughout the pull. The O2 supplied data looked like an EFI map.

The Carter Edelbrock carb simply is not intended for hard core performance. Open the throttle (on a dry one) and look up through it from the bottom. Nothing is smooth, nothing is round, and there is a bunch of stuff hangin into the breeze. Not good for clean airflow. Done.

The Holley is lots better from an air management perspective. And the BG stuff is a functional clone of it. So now we're talking only features, quality, and cost. Both will work equally.

From a dollars spent view, an out of the box piece is hard to beat - especially if you are willing and able to fuss with things. If you're not comfortable with playing with multiple bleeds and such, an out of the box part might actually keep you out of trouble.

As to features I tend to prefer a carb that's "too big" since the popular formulas are all flawed. They don't take into account the fact that carbs are rated against a 1.5" vac. drop - a built in restriction. You need the restriction to generate a comparative rating value, but you don't want it on an engine! Then we work to tune around the big carb by trying to increase the signal at the booster so that we have enough "solid" fuel flow to tune with. Signal increase can come through downleg or annular boosters and booster position relative to the main venturi, as well as tweaks on the booster profile (skirts, undercuts). Now the bleed work becomes really a matter of introducing air leaks to reduce signal and fuel flow at various points in the curve.

The original intermediate circuit designs were for NASCAR where they would floor the car from 2/3 throttle coming off of a turn. There would be a huge hole in the fuel since the accelerator pump would not work at that throttle opening. Hence the intermediate was always pig rich - - it served as an air driven pump circuit! Back before drag guys realized how much fun they could have playing with them, it was pretty common the block off the intermediate completely. Still not a really bad idea on street cars. That O-8082 will run pretty darn nice on the street when you hang a set of annular booster in it....and pull a few jets out.

From my experience with the AFB carbs is they seem to make about the same amount of power as a similar Holley but to be fair I've always tested them on a fairly mild engine. I did some carb testing on my 460 that I built for my '79 Ford pickup. One evening just for fun we tried a Holley 750vacuum, the stock Ford Holley off of the truck, a Carter AFB and a Carter Competition Series Thermoquad.

On my dyno the Thermoquad made the best horsepower and the stock Ford Holley made the best torque but the difference in the numbers between all of the carbs, best to worst was no more than 4 horsepower and about 4 lbs/ft torque.

I really wish Edelbrock would start making the Thermoquad again. The one I've got is an EXCELLENT running carburetor on any engine I've ever tried it. In fact, in one test it beat a supposedly well built Holley(actually a very poorly modified piece) by over 15 horsepower much to the suprise of it's owner. All that money only to get beaten by a plastic carburetor...

that doesn't get the recognition it deserves. Off-roaders like it because it operates at any angle, has great throttle response, gets good fuel economy and is available in an 850 cfm model.

May God's Grace Bless You.

1978 BRONCO: 508" stroker, TFS Street heads, A/C, Lentech Strip Terminator AOD-FRPP wide ratio gearset, Atlas II Highlander transfer case, performance built Dana 44/60-lockers & 4.10 gears, 4 wheel disc brakes, heim joint cross-over steering, 4" suspension lift, 35" mud tires.

I personally like Q-jets. No, I don't own any chevy stuff but an Olds instead. It is not an all-out performance piece, and is quite complicated, but are possibly one of the best street carbs around.

Excellent fuel economy and throttle response from small primaries, but plenty of flow capacity. And they are real cheap as most chevy dudes are too stupid to rebuild them properly! I got the one on my '72 442 for FREE!!! It worked measures better than the 600 Edelbrock that was on the 455 before.

I would urge you to try one on a 460, if I still had one I would. I would like to try a thermoquad but I haven't found one around for my budget (cheap...)

My '78 Fairmont has dual 500 edelbrocks on its 306. Still tuning....

For a high-effort street strip ride I would try a 850 annular Mighty Demon. I don't think much if any difference from a well-tuned holley could be seen, though.

Cheers,
Andy

Some of the 429 CJ cars came with them from the Ford factory ... as I understand it.

The Edelbrock Performer RPM intake is set up to bolt a Q-Jet directly onto.

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71 CJ Motors had a quadrajet, SCJ motors had a Holley

I saw where you had posted having some luck with tunning 8896's for the street.I just recently got one and it runs well wot, put idle and part throttle do not.It burble's at part throttle and is rich on idle.

My motor is a 466 .640ish solid, 12:1, 3000 stall, offy single plane. alum CJ's.

I've had a lot of success tuning 4150's, but this is my 1st dominator. I want to get all the info I can before I start changing a bunch of parameters.

any help would be greatly appreciated.

Thanks Casey

I had an 8896 and sold it and got the two-circuit 8082, since its essentially alot leaner on the idle & transition circuits. Regarding the 8896, the idle & transition circuits, as well as the intermediate circuit, are way way too rich, as confirmed by on O2 sensor and Quickfuel people I spoke with. The main circuit is OK, (main jet & power valve circuit). The idle & transition circuit is jetted from fixed, non-changeable (not easily anyways) fluid jet restriction and the idle air bleed. The emulsion feeds both the idle circuit and the transition circuit. The idle mixture screws merely limit the amount of the emulsion. But they both use the same emulsion/mixture. So you must lean this out by enlarging the idle air bleed by about .008-.010 or so. I forget exactly but alot. Holley says no more than .003-.005 on air bleed changes but that wont do it. Unlike main jets, you can drill these; Holley only sells in packs of (10). The intermediate circuit is way way too rich. The is no real fluid jet to speak of in this circuit to reduce, so again air bleeds open way up from .050 to .070 I believe. Whatever size it had, it got enlarged by .020, whicj is alot. The delays the activation of the circuit but this actually helped too. I also installed fluid jets in the metering blocks, right where the intermediate tubes flow from. I had .050 ID diamater brass tubes, which were .25 long. This combo worked reasonably well, but I still believe this intermediate circuit was unnecessary, and way too rich, so I got a two-circuit which works much better on similar engine. So in summary, if you open up idle/transition and intermediate air bleeds by alot (.010-.020), it will help immensely.

As I stated in my previous post, the E-brock definately has it's place on MILD applications. You can run them in a BB motorhome up to 6,000ft and not have the BS(rich) the multi-piece Holley's put out and you may even squeeze a little more fuel economy out of them. Both the T-Quad and the Q-Jet are excellent carbs on proper application. There are guys running in the stock apprearing classes in the low 11's with a properly tuned Q-jet and I also run one on my Cad. I have seen some real good running T-Quads as well. It doesn't mean you won't achieve the same with a Holley, sometimes it just isn't necessary as they are not the only carb out there. I am certainly no expert on every carb, but I have an example:

I ran 12.97@ 108.8 mph in a stock(no exhaust) '70 Caddy Eldo parts car with a Performer intake/E-brock 750 carb. w/ electric choke@ 4,440 lbs(slightly lightened), 3.07 gear and 150hp shot ...you think the carb wasn't working? I have a stack of time slips. The thing was consistent mph wise, just no traction. If you want to drag race an FWD Eldo...don't.

Rick

Do you have a kinda choppy sound from your car say between 1,800 to 2,500 rpm with your 1000 HP carb.And what kind of fuel do you run in your car.Here's my combo 1989 Mustang Coupe,466,flattop SRP pistons,Eagle Rods,Herbert Solid Roller cam .670-.690 lift 256-266 .050 duration,Victor Intake,Holley 1000 HP carb,about a 5/8" carb spacer,86-93 jets,C-4 trans and 3.73 gears.Here's the thing between 1,800 to 2,500 it has that choppy sound i was talking about.I thought maybe it was to lean since the plugs always come out looking real clean.But when i richened it up seemed like it got worst.I was always using AV gas in it but just mixed some 94 Sunoco with the AV gas.I had a 850 downleg DP on this motor a couple years ago and i don't think i ever noticed this problem with that carb.I bought the 1000 HP carb for only $375.00 off the N.M.R.A boards,so i can't complain about the price i guess.Sorry about writing a book.

Thanks Mark.

I would try inserting a restrictor into the idle feed restriction to lean the mixture in the idle and transision circuits before doing anything else. I would start with a small piece of wire, something around .012 or so. Take a piece of stranded copper wire and use one of the strands. It's easy to insert a piece about 1/2 inch long through the hole and then bend it so that it stays in place. Put the carburetor back together and try it, see if it wants to surge (too lean) or it's much better(most likely). You will have to adjust the idle screws slightly farther out to compensate but not much. You might want to experiment with a larger or smaller wire depending on what it wants till you get it just right. This is VERY important because it saves gas and wear on the engine by having the transision circuit right. Another fact to remember and it's something that many folks over look is that the idle and transision circuits are ALWAYS working. Even at wide open throttle they are still a part of the picture. Their influence becomes less and less but it's still in there so therefore it pays to get it right or at least much closer.

This is an easy mod to try because it's easy to undo and it won't involve modifying anything on your carburetor.

you wouldnt happent o have a diagram or picture to so I could be sure as to which hole to put the wire in?

Thanks Casey

Mark,

I run 92 pump gas for the most part...that's as good as it gets around here. I had a barrel of 100 unleaded in the shop and it always seemed to run a little better with a couple gallons mixed in. I can't say that I have experienced any of the 'choppy sounds' you mentioned. I bought my carb on the Bay from a guy who had it on a pretty ratty Mopar 440 very briefly. He explained something similar you have mentioned and he never got it running very well. The carb is a custom job intended for his application but it seems to work pretty well on my 521, maybe it's my smallish cam. I am no carb expert, but I feel Dave McLain has nailed it as a transitional problem. It would be nice to have it on the dyno and see where your A/F ratio is at between 1800-2500rpm. Give his idea a try, at least you are not changing the carb permanently and it will give you an idea of if you are too rich or lean in the transition.

Rick

If you have an electric fuel pump,shut the pump off when you are cruising along and it's burbling,it should clean out and run good just before the carb runs out of gas.My carb was WAY too rich at part throttle also. Hope this helps.Gregg

If i get some more good weather i'll try the things you suggested.The weathermen are calling for snow here in the next couple of days.If they don't put any salt down on the roads i'll try the tricks you suggested and take the car for a ride and see what happens.

Thanks Mark.

you wouldnt happent o have a diagram or picture to so I could be sure as to which hole to put the wire in?

Thanks Casey

What I would like to know is if you're supposed to install the wire strand in each (2) of the idle feed restriction passages (from main well).




1. To discharge nozzle from acc.pump. - 10. To timed spark port
2. To main air bleed. - 11. Fuel bowl vent
3. To main discharge nozzle. - 12. To main air bleed.
4. To Idle air bleed. - 13. To main discharge nozzle.
5. Used w/auxiliary air bleed. - 14. To Idle air bleed.
6. Not use (not drilled). - 15. Dowel for metering block.
7. Dowel for metering block. - 16. Used w/auxiliary air bleed.
8. To curb idle transfer slot. - 17. To curb idle transfer slot.
9. To curb idle discharge. - 18. To curb idle discharge.


1. Acc.pump discharge. - 13. Fuel bowl vent
2. Main air bleed from main body. - 14. Main air bleed from main body.
3. Main passage to discharge nozzle. - 15. Main passage to discharge nozzle
4. Idle air bleed from main body. - 16. Idle air bleed from main body.
5. Air bleed to main well. - 17. Air bleed to main well.
6. Main body dowel. - 18. Timed spark passage.
7. Main air well. - 19. Main body dowel.
8. Idle feed restriction from main well. - 20. Idle feed restriction from main well.
9. Idle fuel from main well. - 21. Idle fuel from main well.
10. Idle transfer to main body to curb idle adjusting screw. - 22. Idle transfer to main body to curb idle adjusting screw.
11. Curb idle discharge. - 23. Curb idle discharge.
12. Powervalve channel restriction. - 24. Powervalve channel restriction.


May God's Grace Bless You.

1978 BRONCO: 508" stroker, TFS Street heads, A/C, Lentech Strip Terminator AOD-FRPP wide ratio gearset, Atlas II Highlander transfer case, performance built Dana 44/60-lockers & 4.10 gears, 4 wheel disc brakes, heim joint cross-over steering, 4" suspension lift, 35" mud tires.

Well as long as theres a lot experience focused here on carbs, I've got a question that's been bugging me for awhile.

For a certain size engine,if an 850 cfm carb with downleg boosters was found to be the optimum, would about a 900 cfm carb with annular boosters provide better part throttle response and fuel economy than the downleg booster carb? The additional 50 cfm is to make up for the restriction of the annular boosters.

Does anyone have a link to websites for Quick fuel or any other carb specialty shops?

If the world was an honest place an 850 annular would flow 850 and a 900 downleg would flow 900....

If your comparing boosters it really depends on what your combination likes. The annular tends to come on sooner in a given application, comes on "solid" once it is flowing, and get weird at a lower airflow velocity level than a downleg.

The downleg comes on a little later, starts out a little fuzzy/drippy/blobby (those are technical terms), but seems to go further on velocity before it gets funky.

Airflow velocity is a function of engine size, RPM, and overall air flow area through the venturii. Your comparison assumes that this is fixed and nonvariable. Either booster can be made to work, and in race engine that see modest RPM band ranges the difference may be very small. A wider RPM band application (street car, Engine Masters) would probably favor the annular.

Thanks very much Barry, that's exactly the input I was looking for.

BTW, the Quick Fuel website is http://www.quickfueltechnology.com/>

They have/carry much more than is on the website, guess they are too busy to update it.

The boosters that are used in a carburetor are always a compromise, some produce a stronger signal, some allow slightly more airflow and some don't do either of these things. All of them have their place too.

From my understanding in a 4150 style Holley the down leg style booster esspecially one that's machined to have a small groove around the ID is the overall best compromise. The reasons are: It produces a good signal with a minimal loss of flow. It produces good mixture distribution and it delivers the fuel to the engine with good atomization. But most importantly, it produces a signal that allows the fuel curve to be controlled and taylored to the engine very effectively using the emulsion and air bleed arrangement of the Holley carburetor. The annular style booster tends to sometimes be too much of a good thing but only under certain conditions. For some reason it can be very in tune and very out of tune I'm not sure why.

The situation changes somewhat with the Dominator style carburetors. In those the annular style booster insert seems to be the best compromise in many instances.

In the Engine Masters' Challenge I never used less than a Competition Carburetion built billet annular insert equiped 1050 Dominator even when pulling the engine down to 2500 on 408cid. It's a dyno test not the real world and it was the best for our combo..

This is a GREAT topic.