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Author Topic:   2 barrel carb
bigcitycowboy
Member
posted October 22, 2003 05:56 PM
Is there such a thing as a 850 2 barrel made by Holley?? The numbers on the carb are 12R 10824B.I saw one for sell the other day. Looked alittle different than a 4412. Any info on this carb. Thx Jeff


KPLugnut
Member
posted October 22, 2003 08:59 PM
To my knowledge, the largest 2bbl Holley ever mass produced was rated at 650cfm. It was the model # 6425, and was a special application carb that had annular discharge venturi sleeves instead of banjo style booster venturi in the throat of the carb.
There was never a 2bbl from the factory (that I've ever heard of) that flowed 850cfm.
Now....
There IS 2bbls out there that are called "split Dominators", that can flow that much, but one needs to keep in mind that the 2bbl carbs are flowed at 3"Hg on the flowbench, and 4bbls are flowed at 1.5"Hg, so one cannot compare flow ratings without knowing this difference.
What I'm getting at is that you can't "split" a Dominator 1200cfm carb and just say "that's two 600's"....

Hope that helps,
KP


tilley88
Member
posted October 23, 2003 01:48 AM
Hey KP, in your opinion what is the actual flow of a non-touched 6425?


KPLugnut
Member
posted October 23, 2003 07:52 AM
Every flowbench is going to yield slightly different numbers.
It's a bit under 650cfm, most likely. But again, flowbench numbers mean nothing when used for "braggin' rights".
It's all about how the airflow is calibrated along with fuel flow and how well the carb is set up for throttle response.

JMHO,
KP


tilley88
Member
posted October 23, 2003 12:29 PM
KP, we had a guy at the track get disqualified for too large a carb using the drop down the carb type go/no go gauge. He he miked the gauge and said it was too small. He offered to let the track promoter take the carb into his possession and let him ship it off to Holley to spec it. Promoter declined. This guy won the race, but was DQ'ed. He races at all the big races, wins everywhere, gets tore down everywhere, so you would think he'd be legal anywhere he went. My questions are this; Who makes these gauges, and where do you get them?


KPLugnut
Member
posted October 23, 2003 01:05 PM
There's several places that make tech guages. Braswell, BLP, etc. There's also no way of knowing exactly where the guages came from that the tech man that particular night was using. I've heard of a tech man using a cut down exhaust valve once, for pete's sake! He made it himself....sheesh...
I find it hard to believe that a tech man can use a no-go guage and determine some part of a carb to be too SMALL unless it was the guage that measures the height of the venturi booster itself. If that guage slips over the booster, you're out. Or maybe it was the guage that measures the inside diameter of the booster? If it falls in, you're done...
Or maybe it was the guage that measured the combined thickness of the throttle shaft, and butterflies?
See, there are several guages commonly used, not just the venturi diameter guage alone.
Let me rephrase that....there SHOULD have been several guages used....

It's hard to answer without knowing the facts and details about that particular incident.

And a side note on guages....they're a precision instrument (or meant to be anyway) and any tech man who just throws them into his toolbox afterwards is not doing his job right, as those little "dings" created on the outside edge of the guage create false readings.
The guages are also not as cheap to purchase as one would think.
Lastly, keep in mind (fwiw) that the venturi guage is measuring a spot on carbs that is NOT a machined measurement done to very close tolerances at all. There have been cases where a Holley carb right out of the box will not pass the guage test.
That is one reason why many top carb builders own guages, so they will be sure they are selling legal carbs.

Hope that helps,
KP


bigcitycowboy
Member
posted October 23, 2003 01:25 PM
hey KP can u take a look at these pics and be able to tell what kinda carb this is. thx jeff
i hope this works first time posting pics


KPLugnut
Member
posted October 23, 2003 02:49 PM
That started out life as a 6425 650cfm 2bbl. It's got the phenolic spacer between body and base that has been made for some years by several carb builders such as C&S Specialties. It's HEAVILY modified and yes, it probably does flow in the mid-700's on a bench calibrated for the 2bbl scale.
It's definitely NOT stock by any means and would only be allowed in a class that just says "it has to be a 2bbl" and has no tech whatsoever.

Is this the carburetor you were asking about as to whether Holley ever made an 850cfm 2bbl? The answer is no, Holley never made one, but C&S and many other builders make hybrid 2bbls from Holley 2bbl cores that they call the "890" or something, and that is exactly what that thing appears to be.

Hope that helps.
KP


66jj
Member
posted October 23, 2003 04:39 PM
is that phenolic spacer imca legal?? im assuming not.

Jeff

madmodshoe
Member
posted October 23, 2003 10:57 PM
Kp, can you really gain that much cfm and still have good throttle response? Thats the reason Detroit started in with the 4bbls isn't it? Wouldn't this particular carb be very fickle and hard to keep in tune?Thanks in advance!


bigcitycowboy
Member
posted October 24, 2003 12:29 AM
KP our rules state any 2 barrel carb or a holley 4412. may remove choke, and only 1.25 carb spacer. doesnt say anything about size or CFM...... what u think??? sounds like they left to open as long as u can read between the lines


KPLugnut
Member
posted October 24, 2003 08:20 AM
Yes, hybrid carbs of that sort tend to have a VERY finicky personality and fine tuning them into their "sweet spot" can be a chore on some motors.
As for the legality of that carb in your class, Cowboy, I'd say they left the rule written like that so they can excersize the classic "judgement call" and leave it open to the tech inspector's mood that night or whether or not he likes you as opposed to a tech man who's working under a rulebook that is specifically spelled out and clear to all those involved.
Ahhh, what a wonderfull world it would be....
One final thought on this...."Bigger is NOT always better"....just ask Ryan Newman (aka Mr. Mileage) :-)

KP


dirtbuster
Member
posted October 24, 2003 10:26 AM
KP

Do you have some insight on how the #12 dodge is stretching fuel. I have my own thoughts but just wondering if you had something else.

KPLugnut
Member
posted October 24, 2003 11:00 AM
They've been running a 750cfm carb instead of the 830cfm carb and working gaining back the 2-4hp loss that the 750cfm carb took away, while reaping the benefits of the mileage improvement.
That information was in an article someone passed me on some NASCAR news site.
Now that most of the other teams are doing the same thing, his "advantage" is not as noticeable.

At least that's what I read, anyway....

It's funny how not so many years ago, Harry Gant was known as the "mileage king" but he didnt' raise nearly the stink that Newman has....yep, the times have changed...

KP

madmodshoe
Member
posted October 24, 2003 10:05 PM
I have spoke with you before about this, but is there really that much to be gained by hogging out a 4412 vs a properly tuned fuel curve, boosters and a tapered spacer? So much of the racing parts industry seems to be about $$$ for the newest, latest, greatest techno piece. Don't get me wrong, it takes the correct pieces and some $$$ to win, but does it really take a $700.00 2bbl to win the local street stock feature? Most everyone on this forum is a budget racer (oxymoron) otherwise they wouldn't be looking for an advantage. So lets have it! Dayton, let cat out of the bag. What's your best performer for 2bbls on a budget? Providing that the rules only state 2bbl, no aerosol. Just in general, as many different motor combo's require different things! Thanks in advance and sorry to put you on the spot!


Donnie Ross
Member
posted October 25, 2003 04:53 AM
the c&s 890 is a good carb to run but like kp says can be finicky to set up but when compared to my 4412 on 406 huge power difference.but throttle response and drivability the 4412 would win on a slick track much easier to control.


KPLugnut
Member
posted October 25, 2003 07:20 AM
Modshoe,
Probably the biggest reason I started Kinetic Performance as a business was because of the reasons you touched on in the carburetor building industry. We don't even HAVE a 2bbl that sells for that high. Not even our Outlaw Gold Series 2bbl (an aerosol-based carb that flows over 700cfm).
There is truly a lot of sales "hype", false promises and catch phrases used in this field (and many others for that matter) that are more of a psychological thing than something that's honestly measurable on the stopwatch or dyno.
BUT....
There really is going to be a noticeable difference between a 4412 that is right out of the box and a modified piece that, say, has 1.75" butterflies, enlarged and recontoured venturi, custom boosters, and a heavily modified metering block. The real trick with that is the builder has to be able to recontour and calibrate the fuel curve when doing those mods so that the carb still meters fuel properly thru all rpm ranges. Otherwise, you're right, on a slick track, the smaller less-modified carb will prevail.
That right there makes the difference, because blindly enlarging holes here and there KILLS throttle response, driveability, and the potential power an engine can make.
So I guess what your question was, is if there really is a difference between a properly tuned stock carb and those high dollar pieces. Well...there is a difference, but one has to be well aware of how to make use of those differences and that is a skill that doesn't usually come in the box with the carb.
I guess what I'm trying to get at is you are right, racers don't HAVE to spend that kind of money to win races.
To get a carb from us that'll win races at that level would only be $400 and it's much less if you have a core carb to start with.

Sorry for rambling a bit. Dang ol' head cold... :-)

KP

madmodshoe
Member
posted October 25, 2003 09:38 AM
Well said. I have seen far to many "new" racers spend way too much for trick parts that utimately end up causing more heartache than pleasure. I already knew what your answer was going to be, but it seems all to many racers are resigned to spend money rather than work to aquire knowledge. I, as well as many others, really do appreciate what you do on this forum. Thanks kp.


Donnie Ross
Member
posted October 26, 2003 06:49 AM
also if the diff between you and the winner is really small and he has a big carb that may be it, but if you are midpack save your money and work on set up. I ran the 890 c&s
vs stock 4412 in back to back tests while there is a power difference it is not 1/2 second a lap, not a cure all if I had it to do over I would by kps carb and save about $500.00.just my opinion


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