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"Big" 4150-type carbs w/ annular boosters #179514
12/31/08 11:41 AM
12/31/08 11:41 AM
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BradH Offline OP
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Anyone had good luck running "big" (1.56+ venturi) 4150-type carbs w/ annular boosters? One of the changes I made to my Gold Claw towards the end of the year was to switch from 1.42" venturi w/ downleg boosters to 1.56" venturi w/ annulars. I was expecting to see some MPH improvement, but the results were about a .02 improvement in 60-ft. time and no improvement in MPH with better atmospheric conditions. It also runs fatter down low and seems to transition onto the main ciruits too quickly on the street, even after some float level & jetting changes.

It sounds like my results aren't that untypical, based on some carb discussions I've had offline w/ a couple of knowledgeable people. However, it does leave me wondering if I should bother trying the 1.59" venturi w/ the annulars, or go back to the 1.42" / downleg combination. The latter definitely ran cleaner on the street, even though I didn't have the idle quite sorted out at the time. It may be that I have to give up some 60-ft. on the track to get the car to run better on the street.

I've also been told I should get a wide-band O2 sensor, but Santa must have forgotten to put that in his bag this year.

Re: "Big" 4150-type carbs w/ annular boosters [Re: BradH] #179515
12/31/08 12:27 PM
12/31/08 12:27 PM
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The 1.59 with annular might be the ticket since the boosters won't be taking up quite so much space. That is, the transition to the main circuit might slow down a little bit and you might pick up some more of the power up top.

I've never really figured out the annular booster vs. downleg thing and I'm not sure many others have either. Holley doesn't really give any clear advice on their 1000HP carb which can be ordered either way. If you call the tech line you mostly just get non-answers on which to use.

Vizard covered the subject a while back and he said that the annular booster design would pick up a lot of power on certain engines that needed the more atomized fuel coming out of the annular boosters. I don't think I ever really figured out exactly what Vizard was saying in that article though.

Re: "Big" 4150-type carbs w/ annular boosters [Re: AndyF] #179516
12/31/08 12:42 PM
12/31/08 12:42 PM
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I think annulars would help atomize fuel better. it seems like your car liked the change to a bigger venturi but the slow speed thru it is causing fuel to drop out of the downleg.

can you switch boosters easily? OriginalRT has a booster tool


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Re: "Big" 4150-type carbs w/ annular boosters [Re: BradH] #179517
12/31/08 01:14 PM
12/31/08 01:14 PM
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My experience with 4150 carbs. with annular boosters is the higher you rev the motor the fatter the AFR gets Changing the jets doens't fix it either, both of the carbs shop in SO CA that I talk to said to switch them(830 CFM 4150 carbs) to downlegs so I did. I do have two 1000hp 4150 with annular boosters off a tunnel ram set up that I bought and haven't used yet, I did loan one out to a fellow bracket racer that runs a 440 in a Duster, he made one run and took it off because it didn't have jet extensions in the rear and bog a little bit off of the line I had a set of extensions in the trailer but he didn't want to try it again, he said that it ran good in the pits, idle clean and ran good after the bog went away but it did slow down the 60 fts and the 1/4 ET but it may have ran a little bit more mph, but I can't really remember the exact details. I will try them on the tunnel ram soon with the wide ban on the car and on the engine dyno when I dyno it.


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Re: "Big" 4150-type carbs w/ annular boosters [Re: Cab_Burge] #179518
12/31/08 01:34 PM
12/31/08 01:34 PM
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i tried an annular 2 months ago and couldnt get it fat enough

was plenty fat at idle and cruise though


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Re: "Big" 4150-type carbs w/ annular boosters [Re: sixpackgut] #179519
12/31/08 02:20 PM
12/31/08 02:20 PM
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Quote:

i tried an annular 2 months ago and couldnt get it fat enough

was plenty fat at idle and cruise though


Hows your fuel system measure up


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: "Big" 4150-type carbs w/ annular boosters [Re: Cab_Burge] #179520
12/31/08 02:44 PM
12/31/08 02:44 PM
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Charleston
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Quote:

Quote:

i tried an annular 2 months ago and couldnt get it fat enough

was plenty fat at idle and cruise though


Hows your fuel system measure up




its fine with the six pack. mal 140 return reg. maybe the needle and seats were too small. it was a borrowed carb. i even drilled the PVCR. that helped some

i really dont care, carb is off and gone, i was just doing some testing. carb felt like a bear on the street but fell short on top


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Re: "Big" 4150-type carbs w/ annular boosters [Re: sixpackgut] #179521
12/31/08 04:51 PM
12/31/08 04:51 PM
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Not trying to hijack this thread, usually when you cannot get the carb. rich enough to slow the car down on the top end it is usually a fuel supply problem which can be caused by many things like you already alluded to, to small of size of needle and seat, to small of a pump, line size from the pump, to small of a filter, to small pick up size in the tank and so on, the list is almost endless I had this problem last year with a Magnafuel 275 pump, I couldn't slow the car down or show a enrichment on the wide ban by jetting up, I replaced the 275 with a Magnafuel 300 pump and immediatly slow the car down with the same jetting as with the 275 when I jetted the carbs up and the wide ban changed from 14.2 on the line to 15.1 during the run with the old pump to 12.2 during the complete run with the new pump


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Re: "Big" 4150-type carbs w/ annular boosters [Re: Cab_Burge] #179522
12/31/08 07:57 PM
12/31/08 07:57 PM
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i have a race demon with the removable venturie sleeves. it started as a 825cfm as it was doing dual duties street n strip. i stepped it up to a 1050 when we went race only with more cubes & cam but we had endless jetting issues. BG/Demon tech guys told me to swap it to a 1025cfm & suggested annulars which they supplied @ no cost when i bought the new sleeves.. i noticed that on their spec sheet if you swap in the annulars the cfm rating drops. still haven't fitted the annulars but now that the carb is 1025 cfm it's awesome. great idle, even plug readings. it's surprising what 0.040 more venturie effect can do.

Re: "Big" 4150-type carbs w/ annular boosters [Re: rebel] #179523
01/01/09 03:09 AM
01/01/09 03:09 AM
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I ran the Holley HP 1,000 CFM Vacuum secondary carb with anular boosters and it worked really good for me. I did add the screw-in jet extentions and pluged the power valve on the rear metering block. Also ran the lightet secondary spring and changed the accelerator pump cam for a bit more fuel at launch. The engine ran great on the street and track with very good throttle response, and the air/fuel ratio when checked on the chassis dyno looked very good too.

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Re: "Big" 4150-type carbs w/ annular boosters [Re: 451Mopar] #179524
01/01/09 03:24 AM
01/01/09 03:24 AM
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I just pulled up the chassis dyno data, and from 4500 RPM to 6800 RPM the Air/Fuel ratio was nearly flat, showing between 12.6:1 to 12.8:1

Re: "Big" 4150-type carbs w/ annular boosters [Re: BradH] #179525
06/18/09 06:35 PM
06/18/09 06:35 PM
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BradH Offline OP
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Bringing this one back from the dead because it's time to pull the carb apart to either put it back to the 1.42" venturi w/ downleg boosters OR keep the annulars and go up from 1.56" to 1.59" venturi. I'm leaning towards going back to the downleg setup, but figured it's worth hearing any more input before the wrenches start turning.

Re: "Big" 4150-type carbs w/ annular boosters [Re: BradH] #179526
06/18/09 06:43 PM
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ever try the downlegs with the current sleeve?


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Re: "Big" 4150-type carbs w/ annular boosters [Re: sixpackgut] #179527
06/18/09 07:23 PM
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Quote:

ever try the downlegs with the current sleeve?



Naaaaahhhh... you have to run in the 9's for that combination to work.

Re: "Big" 4150-type carbs w/ annular boosters [Re: BradH] #179528
06/18/09 07:35 PM
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I'd think that for your car (street driven, bigish cam, single plane intake, etc) that the annular boosters would work the best. Typically the annular boosters really help out on the bottom end which you should notice in daily driving. You might not notice the difference at the track because the difference in the torque curve is probably below your stall speed.

Re: "Big" 4150-type carbs w/ annular boosters [Re: BradH] #179529
06/18/09 07:48 PM
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I got too Bgs a 850 annular and a 1000 downleg they both have 1.56 bores and are almost the same carb, we just square jetted the to 87s without the pv up front and are still testing, the annular carb is a little funkey on the set up ya gotta keep tryin till ya get it , I think goin to the 1.59 bore is worth the try , we found that the annular is good down low and trickey to get good wot, My buddys got a annular on his chevy 400 thats dialed in perfect , he picked up .3 after a lot of workin on it from stock out of the box so the potential is there ya just gota find it,

Re: "Big" 4150-type carbs w/ annular boosters [Re: BradH] #179530
06/19/09 12:31 AM
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Brad, have you seen the article that Car Craft did on this subject? They had a Demon carb where they changed venturi sizes as well as booster designs. Seems right up your alley.

Re: "Big" 4150-type carbs w/ annular boosters [Re: AndyF] #179531
06/19/09 09:11 AM
06/19/09 09:11 AM
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Haven't seen the article, IIRC. I've let all my magazine subscriptions expire and don't see this stuff on a regular basis.

EDIT - I'm assuming you mean this article .

"In theory..." I'd think the 1.59" venturi w/ annular boosters would be the best all-around setup. The problem is that moving from theory to reality could take a lot more time getting it dialed in than I probably have to mess with it.

Last edited by BradH; 06/19/09 09:43 AM.
Re: "Big" 4150-type carbs w/ annular boosters [Re: BradH] #179532
06/19/09 10:03 AM
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Yep, that is the article. The picked up almost 100 ft-lbs of torque with the annular boosters at one point in the torque curve. I've seen other dyno tests with similiar results. I've never figured it out exactly but the big cam + single plane intakes combinations seem to be the most likely to pick up big with the annular boosters.

That doesn't mean it will be any faster at the track though because the point where the torque increase is made usually doesn't come into play.

Re: "Big" 4150-type carbs w/ annular boosters [Re: AndyF] #179533
06/19/09 10:32 AM
06/19/09 10:32 AM

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Quote:

Yep, that is the article. The picked up almost 100 ft-lbs of torque with the annular boosters at one point in the torque curve. I've seen other dyno tests with similiar results. I've never figured it out exactly but the big cam + single plane intakes combinations seem to be the most likely to pick up big with the annular boosters.

That doesn't mean it will be any faster at the track though because the point where the torque increase is made usually doesn't come into play.




i think Andy is right about this. what i've personally seen is the annular carbs work best on shorter stroke combos that have less signal to the carb, or any combo that has just a bit tooo much plenum area/port cross section.

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